A Phase II Study of Neoadjuvant PLD/Cyclophosphamide and Sequential nab-Paclitaxel Plus Dual HER2 Blockade in HER2-Positive Breast Cancer

Abstract

Background

Neoadjuvant trastuzumab/pertuzumab (HP) plus chemotherapy for HER2-positive breast cancer (BC) achieved promising efficacy. The additional cardiotoxicity still existed. Brecan study evaluated the efficacy and safety of neoadjuvant pegylated liposomal doxorubicin (PLD)/cyclophosphamide and sequential nab-paclitaxel based on HP (PLD/C/HP-nabP/HP).

Patients and Methods

Brecan was a single-arm phase II study. Eligible patients with stages IIA-IIIC HER2-positive BC received 4 cycles of PLD, cyclophosphamide, and HP, followed by 4 cycles of nab-paclitaxel and HP. Definitive surgery was scheduled after 21 days for patients completing treatment or experiencing intolerable toxicity. The primary endpoint was the pathological complete response (pCR).

Results

Between January 2020 and December 2021, 96 patients were enrolled. Ninety-five (99.0%) patients received 8 cycles of neoadjuvant therapy and all underwent surgery with 45 (46.9%) breast-conserving surgery and 51 (53.1%) mastectomy. The pCR was 80.2% (95%CI, 71.2%-87.0%). Four (4.2%) experienced left ventricular insufficiency with an absolute decline in LVEF (43%-49%). No congestive heart failure and ≥grade 3 cardiac toxicity occurred. The objective response rate was 85.4% (95%CI, 77.0%-91.1%), including 57 (59.4%) complete responses and 25 (26.0%) partial responses. The disease control rate was 99.0% (95%CI, 94.3%-99.8%). For overall safety, ≥grade 3 AEs occurred in 30 (31.3%) and mainly included neutropenia (30.2%) and asthenia (8.3%). No treatment-related deaths occurred. Notably, age of >30 (P = .01; OR = 5.086; 95%CI, 1.44-17.965) and HER2 IHC 3+ (P = .02; OR = 4.398; 95%CI, 1.286-15.002) were independent predictors for superior pCR (ClinicalTrials.gov Identifier NCT05346107).

Conclusion

Brecan study demonstrated the encouraging safety and efficacy of neoadjuvant PLD/C/HP-nabP/HP, suggesting a potential therapeutic option in HER2-positive BC.

To date, no studies have assessed the combination of trastuzumab/pertuzumab (HP) with pegylated liposomal doxorubicin (PLD) and nab-paclitaxel. This study evaluated the efficacy and safety (especially cardiotoxicity) of concomitant HP-based sequential neoadjuvant chemotherapy with PLD/cyclophosphamide followed by nab-paclitaxel (PLD/C/HP-nabP/HP).

Implications for Practice.

The pathologic complete response was 80.2% (95%C I, 71.2%-87.0%). Four (4.2%) experienced left ventricular insufficiency with an absolute decline in LVEF (43%-49%). No congestive heart failure and ≥grade 3 cardiac toxicity occurred. Age of >30 years (OR = 5.086) and HER2 IHC 3+ (OR = 4.398) were independent predictors for superior pCR. This regimen may provide a new promising treatment option with a relatively higher pCR and lower cardiac toxicity for patients with HER2-positive positive breast cancer. Patients with age of >30 or HER2 IHC 3+ tumors seemed to achieve a higher pCR rate.

Introduction

The overexpression of human epidermal growth factor receptor 2 (HER2) accounts for 15%-25% of breast cancer (BC),¹ which conferred an aggressive phenotype and poor prognosis.² However, the application of targeted drugs as the neoadjuvant therapy significantly improved the survival, tumor resectability, and breast conservation rate of HER2-positive BC.^3,4 A previous trial suggested that the addition of trastuzumab to neoadjuvant chemotherapy increased the pathological complete response (pCR) rate significantly compared with the chemotherapy-alone arm (65.2% vs. 26.3%, P = .016).⁵ In addition, increasing studies demonstrated that neoadjuvant dual-target therapy-based regimens were superior to single-target therapy-based regimens.⁶ In the KRISTINE trial, patients with dual HER2 blockage (trastuzumab plus pertuzumab [HP]) plus chemotherapy in the neoadjuvant setting of HER2-positive early-stage BC achieved an absolute difference of −11.3% in the pCR rates.⁷ Moreover, further improvements in pCR rates were achieved with the administration of dual anti-HER2 therapy with HP in the NeoSphere and TRYPHAENA trials.^8,9 Taken together, dual HER2 blockade plus chemotherapy as neoadjuvant therapy have been extensively used in HER2-positive BC, including operable subjects.

Several trials demonstrated that concurrent administration of trastuzumab with neoadjuvant chemotherapy could achieve high pCR.^5,10 Nonetheless, the additional cardiotoxicity as primary safety endpoint induced by dual-target-based chemotherapy required specific attention.¹¹ Nonetheless, this regimen was not recommended for anthracycline-based chemotherapy backbone due to cardiotoxicities with concurrent doxorubicin in the pivotal metastatic trial.¹² However, recent studies suggested that compared with conventional anthracyclines, the application of pegylated liposomal doxorubicin (PLD) has shown better efficacy and lower specific toxicities.^13-15 The data regarding cardiotoxicity were particularly encouraging, with a lower incidence of asymptomatic (~10%) and symptomatic cardiotoxicity (~2%).^13,14,16 In addition, substituting solvent-based paclitaxel with nanoparticle albumin-bound (nab)-paclitaxel significantly increased progression-free survival (PFS)¹⁷ and the proportion of patients achieving a pCR rate after anthracycline-based chemotherapy.^18-20 Meanwhile, the safety of the preferred nab-paclitaxel in therapy seemed manageable and promising. Especially, the incidence of serious cardiotoxicity (grade 3 or more) in patients with nab-paclitaxel was lower than solvent-based paclitaxel (0.17% vs. 0.33%).¹⁸

To date, no studies have assessed the combination of HP with PLD and nab-paclitaxel. Further elucidation of the efficacy and the cardiac safety of this combination regimen is required. In the Brecan study, we evaluated the efficacy and safety (especially cardiotoxicity) of concomitant HP-based sequential neoadjuvant chemotherapy with PLD/cyclophosphamide followed by nab-paclitaxel (PLD/C/HP-nabP/HP).

Materials and Methods

Study Design

The Brecan study was an investigator-initiated, single-arm, open-label, phase II clinical study (Trial registration ID: NCT05346107) conducted at the Xijing Hospital of the Air Force Military Medical University (Xi’an, China). This study was approved by the Medical Ethics Committee of Xijing Hospital (No. KY20223267-1) and was conducted in accordance with the Declaration of Helsinki (revised in 2013), the International Conference on Harmonization of Good Clinical Practice guidelines, and applicable local laws and regulations. The primary goal of this study was to evaluate the efficacy and safety of sequential chemotherapy plus concomitant dual HER2 blockade as neoadjuvant therapy for patients with HER2-positive early-stage BC. The patients were informed of the investigational nature of the study and provided written informed consent before registration.

Patient Population

Eligible female patients were aged 18-80 years with histologically or cytologically confirmed HER2-positive BC (stages IIA–IIIC; cT2-3/N0-1/M0), according to the American Joint Committee on Cancer’s Staging System for Breast Cancer (the eighth edition).²¹ Patients with Eastern Cooperative Oncology Group Performance Status (ECOG PS) of 0-1, left ventricular ejection fraction (LVEF) of ≥55%, a minimum of 3-month predicted survival time duration, and adequate organ function were included.

Patients with metastatic BC (stage IV), inflammatory BC, and a history of heart, liver, kidney, or psychiatric disease were ineligible for this study. Additionally, patients who had previously received other HER2-targeted therapies (including trastuzumab, pertuzumab, and pan-HER tyrosine kinase inhibitors [TKIs]), chemotherapy, endocrinotherapy, or radiotherapy were excluded from the study. Pregnant or lactating patients, as well as patients with childbearing potential who did not use contraception if sexually active, were also excluded. Detailed eligibility criteria were listed in Supplementary Table S1.

Procedures

Eligible patients intravenously received PLD (35 mg/m²), cyclophosphamide (600 mg/m²), trastuzumab (8 mg/kg loading dose and then 6 mg/kg), and pertuzumab (840 mg loading dose and then 420 mg) on day 1 every 3 weeks for 4 cycles. Subsequently, 4 cycles of nab-paclitaxel (260 mg/m²), trastuzumab (6 mg/kg), and pertuzumab (420 mg) were intravenously administered on day 1 of each cycle. Definitive surgery was scheduled for patients who completed neoadjuvant therapy (after 21 days) or experienced intolerable toxicity. The type of surgery (modified radical mastectomy or breast-conserving surgery) depended on the patient’s choice or surgical indications. Adjuvant therapy was conducted as per postoperative pathological examination, with a recommendation to complete a total of 1 year of dual HER2 blockade with trastuzumab (6 mg/kg) and pertuzumab (420 mg) for patients with pCR or trastuzumab emtansine (T-DM1) treatment for non-pCR. In parallel, endocrine therapy was given together with postoperative adjuvant therapy for hormone receptor (HR)-positive patients. Asymptomatic LVEF reductions were managed according to a protocol-specified cardiac toxicity algorithm.²² To investigate the true toxicity of this neoadjuvant regimen, no granulocyte-colony stimulation factor (G-CSF) in primary prophylaxis was used in all enrolled patients; however, prophylactic G-CSF was given in the next treatment cycle if febrile neutropenia (FN) or grades 3-4 bone marrow suppression occurred in the previous treatment cycle.

Dose and schedule modifications of study drugs varied according to severity, duration, and occurrence of toxicity (Supplementary Tables S2 and S3). All study drugs should be simultaneously delayed or suspended. Generally, dose adjustment of trastuzumab was not recommended unless the body weight of subjects changed ≥10% from the baseline. Of note, pertuzumab was meanwhile discontinued when trastuzumab was withdrawn. An overview of the therapeutic procedures was shown in Fig. 1.

Figure 1.

Treatment schedule. The treatment procedures for patients with HER2-positive breast cancer. PLD = pegylated liposomal doxorubicin, HER2 = human epidermal growth factor receptor 2, pCR = pathological complete response.

Assessments

Tumor responses were assessed by imaging (mammogram, bilateral breast ultrasound, or magnetic resonance imaging [MRI]) at baseline, every 2 cycles, and before surgery (after 8 cycles of neoadjuvant therapy). The radiological response was evaluated by investigators as per Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1.²³ The pCR was assessed by the local pathology review of the resected breast specimens and ipsilateral axillary lymph node tissues after neoadjuvant therapy according to the Miller & Payne system.²⁴ Safety was assessed by adverse events (AEs) and severity. AEs were confirmed by vital signs, electrocardiogram, ECOG PS, physical examination, and laboratory tests (including hematology, serum biochemistry, and urinalysis). AEs were graded according to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) version 5.0.

Cardiac assessments included a careful clinical evaluation for signs or symptoms of congestive heart failure (CHF) with an electrocardiograph and echocardiogram. LVEF was measured with an echocardiogram. A drop in LVEF was to be reconfirmed within 3-4 weeks of occurrence. Clinical cardiac assessment occurred at baseline, before each cycle of therapy, post cycle 8, and at each follow-up visit. An electrocardiogram weekly evaluation and LVEF assessments were conducted at baseline, within 2 days before day 1 of every cycle during the neoadjuvant period, within 7 days before surgery, and then every 3 months during the adjuvant therapy, for a total of 12 months.

Biomarker Analysis

For biomarkers analysis, tumor tissues were collected at baseline and evaluated for potential biomarker expression by independent pathologists. The expression of HER2 status was immunohistochemically analyzed according to the 2010 American Society of Clinical Oncology/College of American (ASCO/CAP) Guidelines.²⁵ HER2 positive was defined by the ASCO/CAP Guidelines and confirmed according to local assessment.²⁶ Patients with immunohistochemistry (IHC) 3+ tumors were diagnosed as HER2 positive, and HER2 was identified positively by fluorescence in situ hybridization (FISH) for patients with HER2 IHC 2+ tumors. The detection and analysis of HER2 were detailed in Supplementary Methods.

DNA was extracted from the paraffin blocks of tumor tissues and was analyzed for the mutations in the BRCA1 and BRCA2 genes. Patients were categorized by BRCA status as follows: i) BRCA mutated: harboring “pathogenic” or “likely pathogenic” BRCA1/2 variants in germline DNA; ii) BRCA wild type: harboring wild-type BRCA1/2 and benign variants. Patients with BRCA1/2 genetic variants of “unknown significance”: insufficient data to be considered pathogenic mutations.

Endpoints

The primary endpoint was pCR, which was defined as the absence of invasive lesions in the breast and axillary lymph nodes (ypT0/is ypN0) after neoadjuvant therapy. Patients with residual in situ carcinoma in resected breast specimens were also counted as achieving the pCR. The key secondary endpoint was the cardiac safety of neoadjuvant therapy assessed by incidence of New York Heart Association (NYHA) classes III-IV HF (type A cardiac events) and LVEF reduction (10% from baseline and to a value of <50% or any absolute decrease in LVEF ≥20%; type B cardiac events). Other secondary endpoints included objective response rate (ORR, calculated as the proportion of patients achieving complete response [CR] and partial response [PR]) and disease control rate (DCR, defined as the percentage of patients with a CR, PR and stable disease [SD]) after 8 cycles of neoadjuvant therapy, breast-conserving rate (BCR), and the overall cardiac and non-cardiac safety profile of the regimen up to 1 year after surgery. CR was defined as the complete disappearance of all measurable lesions for at least 4weeks. Taking as reference the baseline sum diameter, PR was defined as ≥30% decrease in the sum of the maximum diameter of measurable lesions for at least 4 weeks, without new lesions appearing. Progressive disease (PD) was defined as the appearance of any new lesions or ≥20% increase in the size of the existing lesions. SD was defined as less than 30% decrease and less than 20% increase without the appearance of new lesions. Moreover, the exploratory endpoint was the association between pCR and potential biomarkers in tumor samples.

Statistical Analysis

Sample size estimation was based on the primary endpoint of pCR. From the pCR reported in the Opti-HER HEART study,²² we regarded a proportion of patients with a pCR of 74.0% or more as proof of the efficacy of the combination and of less than 56.6% as insufficient to continue the assessment. Eighty-one cases were enrolled with the one-sided α error of 5% and power of 90%. A total of 90 patients were recruited, considering an approximate dropout incidence of 10%.

Efficacy analysis was performed in the intention-to-treat (ITT) population, which was defined as all participants who received at least one dose of the study treatment. Safety analysis was performed in the safety analysis set (SAS), which was defined as the ITT population with safety records.

Patient characteristics, safety outcomes, and tumor responses were summarized descriptively. Categorical variables were summarized as frequencies (percentage [%]), and continuous variables were presented as medians with interquartile range (IQR) or range. The 95% confidence interval (CI) of the ORR and DCR were calculated using the Clopper-Pearson method. Statistical comparisons of pCR according to clinicopathological factors were performed using the Chi-square test. Univariate and multivariate analysis was performed using logistic regression for corresponding clinicopathological factors associated with pCR and reported with an odds ratio (OR) and 95%CI. OR <1 implied a lower risk of progression or death with the exposure in patients. All statistical tests were 2-sided, with significance set at P < .05. All statistical analyses were performed with SPSS software (version 22.0, SPSS Institute, IL, USA).

Results

Patient characteristics

Between January 2020 and December 2021, 120 patients were screened for eligibility, and 96 were ultimately enrolled in this study and received neoadjuvant therapy. A total of 96 patients were included in the ITT and the SAS (Fig. 2). The baseline characteristics of the 96 patients are presented in Table 1. All patients had a median age of 49 (range, 21-71 years) years and the majority of the patients were aged >30 (78/96, 81.25%). Only 1 (5.6%) patient experienced BRCA mutation in totally 18 patients with age of ≤30 years. The median tumor size was 3.5 (range, 2.0-6.3 cm) cm. Most (91/96, 94.79%) patients had T2 tumors. The majority were pre-menopausal (56/96, 58.3%) and had HR-positive (58/96, 60.42%) disease. HER2-positive mainly included IHC 2+/FISH+ (50/96, 52.08%). The median follow-up time was 11.2 (IQR, 5.4-16.9 months) months at the data cutoff of December 2021.

Figure 2.

Trial profile. ITT = intention-to-treat, SAS = safety analysis set.

Table 1.

Baseline characteristics.

Characteristics	All patients (N = 96)
Age, years-median (range)	49 (21-71)
≤30	18 (18.75%)
BRCA mutation	1 (5.6%)
>30	78 (81.25%)
Tumor size, cm-median (range)	3.5 (2.0-6.3)
Tumor stage
T2	91 (94.79%)
T3	5 (5.21%)
Lymph node status
Negative	45 (46.88%)
Positive	51 (53.12%)
Hormone receptor status
ER and/or PR positive	58 (60.42%)
ER and PR negative	38 (39.58%)
HER2 status
IHC 2+/FISH+	50 (52.08%)
IHC 3+	46 (47.92%)
Histologic grade
1	15 (15.63%)
2	43 (44.79%)
3	38 (39.58%)
Menopause
No	56 (58.3%)
Yes	40 (41.7%)

Data are presented as the median (range or interquartile range [IQR]) or n (%). HER2 = human epidermal growth factor receptor 2, IHC = immunohistochemistry, FISH = fluorescence in situ hybridization, ER = estrogen receptor, PR = progesterone receptor.

Treatment Exposure and Surgery

Of the 96 patients enrolled in the ITT population, 95 (99.0%) patients completed all planned 8 cycles of neoadjuvant therapy, whereas 1 (1.0%) discontinued due to disease progression and ultimately received a mastectomy. Ninety-five (99.0%) patients subsequently received adjuvant therapy. Thereinto, 77 (100.0%) patients with pCR had the dual HER2 blockade with HP, and 2 (10.5%) patients with non-pCR received T-DM1 treatment due to economic burden.

All underwent surgery, of whom 45 (46.9%) patients had breast-conserving surgery and 51 (53.1%) received mastectomy. Thirty (31.3%) treatment and coronavirus pandemic-related surgical delay occurred in this study, and the median interval between the last administration of neoadjuvant therapy and surgery was 23 (range, 21-28 days) days.

No patients required dose reductions. Fifteen (15.6%) patients experienced a dose delay of 1 week due to peripheral sensory neuropathy and febrile neutropenia. The median relative dose intensity (RDI) across all drugs was 100.0%.

Efficacy

Seventy-seven (80.2%; 95%CI, 71.2%-87.0%) patients of 96 patients achieved a pCR in the breast and axilla (Table 2) and 19 (19.8%; 95%CI, 13.1%-28.9%) did not.

Table 2.

Curative effect of neoadjuvant therapy schemes.

	All patients (N = 96)
Pathological data
pCR	77 (80.2%, 71.2%-87.0%)
Non-pCR	19 (19.8%, 13.1%-28.9%)
Imaging data
ORR	82 (85.4%, 77.0%-91.1%)
DCR	95 (99.0%, 94.3%-99.8%)
CR	57 (59.4%)
PR	25 (26.0%)
SD	13 (13.5%)
PD	1 (1.0%)

Data are presented as n (%) or n (%, 95% confidence interval).

Abbreviations: pCR, pathological complete response; CR, complete response; PR, partial response; SD, stable disease; PD, progressive disease; ORR, overall response rate; DCR, disease control rate.

With respect to imaging data, ORR was observed in 82 (85.4%; 95%CI, 77.0%-91.1%) patients, including 57 (59.4%) CR and 25 (26.0%) PR, per RECIST v.1.1, respectively (Table 2). The number of patients who achieved SD was 13 (13.5%); thus, the DCR was 99.0% (95%CI, 94.3%-99.8%). Only 1 (1.0%) patient had PD. Moreover, 57 (57/77, 74.0%) of pCR patients achieved CR, while other (20/77, 26.0%) patients with carcinoma in situ achieved PR. Of 19 non-pCR patients, 13 (68.4%) achieved SD, 5 (26.3%) achieved PR and 1 (5.2%) achieved PD (Fig. 3).

Figure 3.

Tumor response. Waterfall plot of tumor size change from baseline to maximum percentage in each patient as per RECIST version 1.1. CR, complete response; PR, partial response; PD, progressive disease; SD, stable disease.

Safety and Tolerability

Cardiac Toxicity

The mean LVEF at baseline was 62.8% (range, 56%-70%). No patients missed or did not perform at least one LVEF assessment within the protocol-specified interval. Left ventricular insufficiency was observed in 4 (4.2%) patients, with a decrease in LVEF up to 48%, 43%, 49%, and 48% from baseline, respectively (Fig. 4). No symptomatic CHF and ≥grade 3 cardiac toxicity, and cardiac deaths occurred.

Figure 4.

Left ventricular ejection fraction (LVEF) changes during neoadjuvant treatment in the intent-to-treat population.

Overall Safety

All AEs in the SAS population were presented in Table 3. All safety populations experienced at least one AE. Common AEs of any grade were neutropenia, anemia, peripheral sensory neuropathy, nausea, asthenia, and drug-induced liver injury. Grade 3 or higher AEs occurred in 30 (31.3%) patients and mainly included neutropenia (29/96, 30.2%), of which 9 cases (9/96, 9.4%) had febrile neutropenia, followed by asthenia (8/96, 8.3%) and peripheral sensory neuropathy (7/96, 7.3%). G-CSF was initiated in 29 (30.2%) patients. Fifteen (41.7%) patients required dose adjustments of neoadjuvant therapy following the AEs. No patients discontinued due to AEs. No AEs of grade 5, SAEs, or treatment-related deaths were observed.

Table 3.

Adverse events of neoadjuvant therapy in patients with HER2-positive breast cancer.

	Safety population (N = 96)
	Grade 1	Grade 2	Grade 3	Grade 4	All grade
Neutropenia	28 (29.2%)	31 (32.3%)	15 (15.6%)	5 (5.2%)	79 (82.3%)
Febrile neutropenia	0	0	5 (5.2%)	4 (4.2%)	9 (9.4%)
Anemia	46 (47.9%)	22 (22.9%)	0	0	68 (70.8%)
Thrombocytopenia	15 (15.6%)	6 (6.3%)	0	0	21 (21.9%)
Left ventricular dysfunction	2 (2.1%)	2 (2.1%)	0	0	4 (4.2%)
Dry skin	5 (5.2%)	6 (6.3%)	0	0	11 (11.5%)
Peripheral sensory neuropathy	46 (47.9%)	33 (34.4%)	7 (7.3%)	0	86 (89.6%)
Peripheral edema	2 (2.1%)	0	0	0	2 (2.1%)
Mucositis	33 (34.4%)	13 (13.5%)	4 (4.2%)	0	50 (52.1%)
Vomiting	30 (31.3%)	15 (15.6%)	2 (2.1%)	0	47 (49.0%)
Diarrhea	26 (27.1%)	23 (24.0%)	3 (3.1%)	0	52 (54.2%)
Nausea	44 (45.8%)	26 (27.1%)	3 (3.1%)	0	73 (76.0%)
Asthenia	57 (59.4%)	21 (21.9%)	8 (8.3%)	0	86 (89.6%)
Increased ALT concentration	43 (44.8%)	28 (29.2%)	5 (5.2%)	0	76 (79.2%)
Increased AST concentration	44 (45.8%)	30 (31.3%)	5 (5.2%)	0	79 (82.3%)

Data are N (%).

Biomarker Analysis

The pCR of the evaluable patients was outlined according to clinicopathological characteristics in the subgroup analyses (Supplementary Table S4). In China, female BC was strongly related to age,²⁷ with the increasing Chinese BC patients being younger than 30 years of age with poor prognosis.²⁸ The proportion of this population was up to ~20% in our study and we thus focused on this population. Therefore, the age of 30 years was set at the cutoff value. Age (14.29% in the ≤30 years group vs. 85.71% in the >30 years group; P = .02) and HER2 status (46.75% in the IHC 2+/FISH+ group vs. 53.25% in the IHC 3+ group; P = .04) were found to be associated with pCR. No differences were found between other clinicopathological factors and pCR (P > .05). Although the pCR of the HR-positive patients was numerically higher than that of the HR-negative patients (82.8% vs. 76.3%), the difference was not statistically significant (P = .44).

We further evaluated the association between the expression of the biomarker measured at baseline and pCR (Supplementary Table S5). According to the univariate analysis, age and HER2 status were significant predictors of pCR. Moreover, age and HER2 status were also independent predictors of pCR by the multivariate logistic regression analysis. Age of >30 was significantly associated with a higher pCR rate. Age of >30 was significantly associated with a higher pCR rate (P = .01; OR = 5.086; 95%CI, 1.44-17.965). Compared with HER2 IHC 2+/FISH+ tumors, HER2 IHC 3+ tumors were associated with a higher likelihood of achieving a pCR (P = .02; OR = 4.398; 95%CI, 1.286-15.002).

Discussion

Based on the AC-THP regimen as the level I recommendation for HER2-positive BC,²⁹ we additionally used the HP at the early stage of neoadjuvant therapy and improved dosage forms of anthracycline (to PLD) and paclitaxel (to nab-paclitaxel) to limit the toxicity of chemotherapy. Results from the Brecan study suggested that the regimen including the active drugs (trastuzumab, pertuzumab, paclitaxel, and anthracycline) for HER2-positive BC was effective and achieved an encouraging pCR (80.2%). In parallel, no episodes of symptomatic HF and cardiac deaths were observed, and only 4.2% experienced asymptomatic cardiac events.

Despite recent controversies surrounding the role of anthracyclines in the adjuvant treatment of BC, these agents remain a cornerstone of therapy. Recently, several further studies have assessed the concurrent administration of trastuzumab and pertuzumab with anthracyclines. The pCR was reported at 56.2% in arm A of the TRYPHAENA trial,⁹ and 56.6% in the Opti-HER HEART trial.²² In contrast, the numerically higher pCR reported in our study was 80.2%. Our findings might be partially attributed to the following reasons. The emerging further understanding of targeted drug delivery showed that the preferential release upon reaching the targets of PLD enhanced tolerability and patients’ compliance, thus resulting in increased anticancer efficacy.^30,31 In parallel, a retrospective study compared the use of traditional anthracyclines and PLD in neoadjuvant therapy for patients with BC. The study revealed higher pCR rates in PLD-based cohorts.³² These data may provide compelling support for the application of PLD in our protocol. In addition, increasing studies indicated that only women with HER2-positive BC might derive incremental benefits from anthracycline use, while most HER2-negative seem not to.^33,34 The higher pCR was merited due to all HER2-positive patients enrolled in this study and thus the results of pCR should be interpreted with caution. It was also important to point out that substituting solvent-based paclitaxel with nab-paclitaxel significantly increases the proportion of patients achieving a pCR rate after anthracycline-based chemotherapy.^18,35 Breast-conserving surgery was performed in 45 patients (46.9%) and mastectomy in 51 patients (53.1%). In spite of a promising BCR of 46.9% and pCR of 80.2%, we observed surprisingly high mastectomy rates, which was consistent with the trend of rising mastectomy rates.³⁶ This trend may be triggered by patients’ preferences to avoid a second future BC despite the evidence indicating that an early stage is highly curable BC with only 0.5-1% annual risk of a new primary cancer in the breast.³⁷ All patients enrolled in the present study had a median age of 49 years and a median tumor size of 3.5 cm. However, 85.4% of patients had objective responses and 99.0% of patients achieved disease control, even 57 (59.4%) patients attained CR. Furthermore, only 30 (31.3%) treatment and coronavirus pandemic related surgical delay occurred, suggesting that our combination regimen could heavily improve patients’ medical compliance and quality of life, especially in the Covid-19 era. Taken together, the impressive efficacy of using this combination as the neoadjuvant therapy seemed favorable.

The identification of predictive biomarkers was particularly important for the selection of optimal candidates for targeted therapy. Thus, we conducted an analysis of the association between potentially sensitive biomarkers and the treatment effects of the proposed regimen. Our subgroup analysis found that pCR was associated with the HER2 status of patients. The pCR rate was higher in tumors with HER2 IHC 3+ than in tumors with HER2 IHC 2+/FISH+ (P = .04). This was consistent with previous studies,^38,39 that is, the pCR rate was highly correlated with the HER2 IHC score in neoadjuvant anti-HER2 treatment. The multivariate logistic regression analysis further confirmed that HER2 status was an independent predictor for better pCR in patients with BC (P = .02; OR = 4.398; 95%CI, 1.286-15.002). The results were consistent with those of a real word study, in which patients with HER2 IHC 3+ tumors had better pCR than patients with HER2 IHC 2+/FISH+ tumors (71.8% vs 13.9%; P < .001; OR,11.958).⁴⁰ Moreover, patients with an age of ≤30 achieved a lower pCR rate than those with an age of >30 and the difference was significant (P = .02). It was suspected that young women may be more likely to have an aggressive and heterogeneous biological subtype of BC compared with older women, thus leading to a lower response.^41-43 Previous studies demonstrated that genetic factors (BRCA mutation status) are even more meaningful in younger patients^44,45 and tumors arising in patients with BRCA mutations were shown to be particularly sensitive to anthracycline-taxane-containing regimens.^46,47 However, only 1 (5.6%) patient experienced BRCA mutation in totally 18 patients with age of ≤30 years, which may contribute to a lower pCR rate in younger patients in our study. Additional analysis indicated that age was the key factor that influenced the pCR with a P-value of.01, OR of 5.086, and 95%CI of 1.44-17.965. Nonetheless, this trial could not differentiate whether the relationship was prognostic or predictive because of its single-arm design. Importantly, all potential biomarkers for monitoring treatment responses to this regimen in patients with HER2-positive BC, require additional observation and confirmation in randomized prospective trials with a larger sample size, which may allow further customization of treatments and prediction of individualized therapeutic responses.

When HER2-targeted agents were combined with anthracyclines, cardiotoxicity was a major concern. Comparisons of cardiotoxicity as common primary safety endpoint across trials were difficult because diverse trials defined cardiotoxicity differently. The proportion of patients experiencing left ventricular dysfunction, while receiving concurrent dual HER2 blockade plus anthracyclines in various clinical trials ranges from ~2%-11%.^9,37,48,49 In the GeparSepto trial,⁴⁹ patients with HER2-positive early BC received 4 cycles of weekly paclitaxel (either solvent-based or nab-paclitaxel) followed by 4 cycles of epirubicin plus cyclophosphamide, with concurrent trastuzumab and pertuzumab and 2.0% of patients showed an LVEF decline to <50%. The definition of cardiac dysfunction in the Opti-HER HEART trial was the same as in our study. The results showed that patients received neoadjuvant trastuzumab, pertuzumab, paclitaxel, and non-PLD for 6 cycles, and 2.4% experienced an asymptomatic type B cardiac events, with the LVEF decline of 45% and 38%.²² In arm A of the phase II TRYPHAENA trial, 75 patients received 6 cycles of HP plus 5-fluorouracil, epirubicin, and cyclophosphamide followed by docetaxel.⁹ Four (5.6%) patients experienced a reduction in LVEF of ≥10% from baseline to <50%, and no patient experienced symptomatic cardiac toxicity. During post-treatment long-term follow-up, the cardiac toxicity remained manageable, with 2.8% of left ventricular systolic dysfunction of any grade and 11.1% of an LVEF reduction.⁴⁸ The cardiac safety showed in above studies using regimens of anthracycline-taxane chemotherapy plus HP supported rational design of our study. Among our 96 patients, we observed no congestive HF or symptomatic cardiac dysfunction, but 4 patients (4.2%) experienced an asymptomatic decrease in LVEF of 43%-49%. In addition, no cardiac toxicity of ≥grade 3 and cardiac deaths occurred. Overall, the application of dual HER2-blockade throughout the neoadjuvant did not significantly increase cardiotoxicity. Given the finding in previous studies,^{15,17,18,50,51} it might be partially ascribed to the alternations of the dosage form of doxorubicin and paclitaxel. Nevertheless, this hypothesis is warranted to be tested in a larger, randomized phase III trial. In parallel, it was critical to consider non-cardiac toxicities when patients receive potentially effective drug combination regimens. In general, the combination was well-tolerated since most cases were mild-to-moderate and were resolved. Of note, the incidence of FN was lower than 20%, which may be ascribed to the use of G-CSF. Moreover, no new safety signal was observed in our study compared with the previous similar studies.

Certain limitations of our study should be acknowledged. First, the present study was limited by the single-arm, non-randomized phase II design and the relatively small sample size, thus assessment of the contribution of the combination regimen in this setting was difficult. Meanwhile, given the relatively small sample size, the number of observed events led to a lack of precision of the estimated rate, which was exacerbated by the fact that patients had a low probability of cardiac events due to their mean age and lack of risk factors. Despite the stringent response evaluation, a limited sample size cannot fully exclude an inclusion bias. Second, long-term cardiac safety was not evaluated and no survival outcome data were available. Therefore, a longer follow-up is warranted to fully assess the benefits of this treatment regimen. Third, this non-global study with data from a single center was conducted only in China, which might affect the generalizability of the results to broader populations. Fourth, the biomarker correlative analyses were exploratory. Therefore, we were limited regarding the ability to identify new biological processes associated with treatment response. As well, the exact distribution of clinicopathological characteristics and potential biomarkers versus cardiac events could not be determined. Nevertheless, the present study confirmed that the combination regimen could be considered a promising neoadjuvant therapy for HER2-positive BC. Further evaluation of this combination therapy in a randomized phase III trial with a larger sample size and longer follow-up period is warranted in the near future.

Conclusions

PLDCHP-nab-PHP regimen showed encouraging anti-tumor activity and manageable safety profiles in the neoadjuvant therapy of patients with HER2-positive early-stage BC. Since the existing neoadjuvant setting for HER2-targeted therapies plus chemotherapy has reached the therapeutic plateau, further improvements in pCR rate and cardiotoxicity in our study may provide a novel feasible therapeutic modality for this population. Further evaluation of this combination regimen in a larger randomized clinical trial is warranted in the near future.

Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Ethical Approval

This study was approved by the Medical Ethics Committee of Xijing Hospital (No. KY20223267-1). All procedures in the present study conformed to the ethical standards of the institutional and/or national research committee, Good Clinical Practice guidelines, and the 1964 Helsinki Declaration and its later amendments or comparable ethical standards. Written informed consent was obtained from each patient.

Conflict of Interest

The authors indicated no financial relationships.

Author Contributions

Conception/design: F.F.L., N.L.L. Administrative support: L.W., F.F.L., N.L.L. Provision of study material or patients: J.X.Y., Y.Q.Y., L.Y., X.X.W. Collection and/or assembly of data: W.Y.H., J.W., J.Y. Data analysis and interpretation: M.L.H., D.D.X., D.C.T. Manuscript writing, revisions, and final approval of manuscript: all authors.

Data Availability

The datasets supporting the results of the present study can be obtained from the corresponding author upon reasonable request.