Abstract
Introduction
Breast cancer in males constitutes approximately 1% of all breast cancer cases globally. Despite extensive treatment experience with abemaciclib in women with metastatic breast cancer (MBC), real-world evidence in male MBC is lacking.
Methods
This analysis was a part of a broader, retrospective study that analyzed electronic medical records and charts of 448 men and women with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) MBC who initiated an abemaciclib-containing regimen from January 2017 through September 2019. Data were collected from the Florida Cancer Specialists & Research Institute and the Electronic Medical Office Logistics Health Oncology Warehouse Language™ databases and summarized descriptively. Real-world best response was described: complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD).
Results
Data for six male patients with MBC who were treated with abemaciclib in combination with an aromatase inhibitor (AI) or fulvestrant are presented. Four patients were aged ≥ 75 years, and four patients had ≥ 3 metastatic sites, including visceral involvement. Abemaciclib was initiated in/after third-line (≥ 3L) in four patients, and patients had history of treatment with AI (n = 4), chemotherapy (n = 3), and/or prior cyclin-dependent kinase 4 and 6 inhibitors (n = 2) in the metastatic setting. Abemaciclib + fulvestrant was the most common abemaciclib-containing regimen (n = 4). Best response was documented in four patients: 1 each with CR, PR, SD, and PD.
Conclusion
Prevalence of male MBC in this dataset was consistent with expected prevalence in the broader population. Most male patients received an abemaciclib-containing regimen in ≥ 3L, with anti-cancer activity observed despite heavy metastatic burden and prior treatments in a metastatic setting.
Keywords: Abemaciclib, Male patients, Metastatic breast cancer, Outcome, Treatment pattern
Key Summary Points
| Why carry out this study? |
| Despite extensive treatment experience with abemaciclib in women with metastatic breast cancer (MBC), there is limited real-world treatment evidence in male MBC. |
| What did the study ask?/What was the hypothesis of the study? |
| This study aimed to add to the body of evidence characterizing the effectiveness of abemaciclib for male patients with hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) MBC treated in the real-world. |
| What were the study outcomes/conclusions? |
| Prevalence of male MBC in this dataset (1.3%) was similar to the prevalence in the broader population with MBC (~ 1.0%) and the abemaciclib-containing regimes were used in ≥ 3L. Anti-cancer activity of treatment was observed despite heavy metastatic burden and prior treatments in metastatic disease. |
| What has been learned from the study? |
| These data add to the limited body of evidence for male patients with HR+, HER2– MBC treated with abemaciclib in routine clinical practice. |
Introduction
Male breast cancer constitutes 0.5–1% of all breast cancer cases globally [1, 2]. More than 90% of male patients have the hormone receptor-positive (HR+), human epidermal growth factor receptor 2-negative (HER2−) subtype, and treatment recommendations for these patients are often extrapolated based on breast cancer treatment in women, despite well-recognized differences in the clinicopathological features between genders [2–6].
The addition of cyclin-dependent kinases 4 and 6 inhibitors (CDK 4&6Is: palbociclib, ribociclib, and abemaciclib) to endocrine therapy has now become standard of care for patients diagnosed with HR+, HER2− metastatic breast cancer (MBC) [7, 8]. Palbociclib [9], ribociclib [10], and abemaciclib [11, 12] are each approved by the United States Food and Drug Administration (US FDA) for the treatment of MBC in males; however, published real-world data are limited. Hansra et al. published a case study of second-line (2L) abemaciclib plus fulvestrant therapy in a male patient with MBC, and reported a complete tumor response [13]. From a real-world study conducted in 15 male patients with HR+, HER2- advanced breast cancer treated with palbociclib, Blum et al. showed that when palbociclib was administered as first-line (1L) in nine patients and as 2L in six patients, one patient experienced complete response (CR), and four patients experienced partial response (PR). Patients received palbociclib in combination with aromatase inhibitor (AI, n = 7), fulvestrant (n = 7), or tamoxifen (n = 1) [14].
Abemaciclib is FDA-approved for use in men with MBC, either in combination with an AI, fulvestrant, or as monotherapy [15]. The purpose of this study is to add to the body of evidence characterizing the effectiveness of abemaciclib for male patients with HR+, HER2− MBC treated in the real world.
Methods
Study Design
This descriptive analysis was a part of a broader retrospective study, which analyzed electronic medical records (EMR) and charts collected from the Florida Cancer Specialists & Research Institute (FCS) and the Electronic Medical Office Logistics (EMOL) Health Oncology Warehouse Language (OWL)™ databases.
Patients (n = 448) diagnosed with HR+, HER2− MBC, who were treated in a US-based community oncology practice with an abemaciclib-containing regimen between January 2017 and September 2019, were included in the initial group of patients for data analysis. From the initial dataset, patients with male breast cancer patients were selected for the planned subset analyses. Patients were followed from the initiation of abemaciclib-based regimen (index date), inclusive, through earliest date of death, loss to follow-up (last structured activity in the EMR), or study end date (December 31, 2019) (Fig. 1).
Fig. 1.
Study design. EMR electronic medical record
There was no overlap or duplication of available patient data from the two databases, and the study was approved with a waiver of consent and a full waiver of Health Insurance Portability and Accountability Act authorization by the Advarra Institutional Review Board.
Patient Population
Male patients aged ≥ 18 years with evidence of breast cancer prior to or at the index date, distant metastatic disease prior to or within 30 days following the index date, and HR+ and HER2− status based on the closest valid test any time prior to or within 60 days following the index date were included.
Patients were considered ineligible for analysis if they were treated with abemaciclib in the context of a clinical trial, were receiving treatment for primary malignancies other than MBC, or did not have ≥ 90 days of follow-up from the index date (patients who died within 90 days of the index date were not excluded).
Patients were classified based on the index abemaciclib-containing regimen, including abemaciclib + AI (letrozole, anastrozole, or exemestane), abemaciclib + fulvestrant, and abemaciclib monotherapy. Patients in combination therapy group received abemaciclib 150 mg twice daily (BID) in combination with fulvestrant or an AI, and those in monotherapy group received abemaciclib 200 mg BID. The reasons for discontinuation were reported for each group.
Assessments and Statistical Analysis
Patient characteristics (age, region, disease stage, metastatic sites, and number of metastatic sites) and treatment patterns (index regimen and index line of therapy) were summarized descriptively. Non-cancer comorbidity burden was characterized using the cancer-adapted Elixhauser comorbidity index [16–18]. Primary endocrine resistance (PER) or secondary endocrine resistance (SER) was defined per European Society for Medical Oncology (ESMO) guidelines [17].
Among patients with response data available in their chart, real-world best response [defined as CR, PR, stable disease (SD), or progressive disease (PD) while on index regimen] as documented in the charts and/or radiology reports was recorded. Patients without documentation of response, indeterminate response, or not defined, were not included in the response calculation.
Results
Baseline Demographics and Clinical Characteristics
A total of six male patients with MBC were identified, representing 1.3% of the cohort of 448 patients in the broader study. Most patients (n = 4) were aged ≥ 75 years. At initial diagnosis, three patients were diagnosed with stage II breast cancer, and one patient each with stage III and stage IV. Stage at initial diagnosis was unknown for one patient. At abemaciclib initiation, three patients had Eastern Cooperative Oncology Group performance status (ECOG PS) 1, one patient had ECOG PS 2, and two patients had unknown ECOG PS. Most patients (n = 4) had ≥ 3 metastatic sites at abemaciclib initiation, including bone (n = 5), visceral (n = 4), and lung (n = 4) metastases. One patient had PER at abemaciclib initiation, and three patients had SER. Endocrine sensitivity status was unknown for 2 patients due to missing data (Table 1). All patients had a cancer-adapted Elixhauser comorbidity index score ≥ 2, three of whom had a score of ≥ 3 (Table 2).
Table 1.
Patient demographics and tumor-related characteristics
| Characteristic | n = 6 |
|---|---|
| Age in years, mean (SD) | 71.2 (16.0) |
| Age groups | |
| ≤ 49 years | 1 (16.7) |
| 50–64 years | 1 (16.7) |
| 75–84 years | 3 (50.0) |
| 85 + years | 1 (16.7) |
| Race | |
| White | 5 (83.3) |
| Other | 1 (16.7) |
| Region | |
| South | 5 (83.3) |
| West | 1 (16.7) |
| Smoking history | |
| Past | 3 (50.0) |
| Never smoked | 2 (33.3) |
| Unknown | 1 (16.7) |
| Disease stage at initial diagnosis | |
| Stage II | 3 (50.0) |
| Stage III | 1 (16.7) |
| Stage IV | 1 (16.7) |
| Unknown | 1 (16.7) |
| ECOG status | |
| 1 | 3 (50.0) |
| 2 | 1 (16.7) |
| Unknown | 2 (33.3) |
| Number of metastatic sites | |
| 1 | 2 (33.3) |
| ≥ 3 | 4 (66.7) |
| Metastases sitesa | |
| Bone | 5 (83.3) |
| Visceral | 4 (66.7) |
| Lung | 4 (66.7) |
| Liver | 1 (16.7) |
| Brain | 1 (16.7) |
| Bone (only) | 2 (33.3) |
| Developed endocrine resistancea | |
| Primary | 1 (16.7) |
| Secondary | 3 (50.0) |
| Unknown | 2 (33.3) |
All data are presented as n (%), unless specified. ECOG status, number of metastatic sites, and metastases site are reported at abemaciclib initiation. Data were collected from FCS and EMOL Health Oncology Warehouse Language™ databases
ECOG Eastern Cooperative Oncology Group, EMOL Electronic Medical Office Logistics Health Oncology Warehouse Language, FCS Florida Cancer Specialists & Research Institute, n number of patients, SD standard deviation
aCategories are not mutually exclusive
Table 2.
Comorbidities at baseline
| Characteristic | n = 6 |
|---|---|
| Patients with history of other primary cancers | 1 (16.7) |
| Cancer-adapted Elixhauser comorbidity index categories | |
| 2 | 3 (50.0) |
| ≥ 3 | 3 (50.0) |
| Cancer-adapted Elixhauser comorbidities | |
| Hypertension | 2 (33.3) |
| Diabetes, uncomplicated | 2 (33.3) |
| Hypothyroidism | 1 (16.7) |
| Renal failure | 1 (16.7) |
| Coagulopathy | 1 (16.7) |
| Weight loss | 1 (16.7) |
| Fluid and electrolyte disorders | 2 (33.3) |
| Deficiency anemia | 1 (16.7) |
All data are presented as n (%)
Most patients had a history of treatment with AIs (n = 4), chemotherapy (n = 3), and/or prior non-abemaciclib CDK 4&6Is (n = 2) in the metastatic setting. Prior ribociclib- or palbociclib-based treatment was discontinued due to disease progression in one patient and due to adverse events/ intolerability in the other patient (Table 3).
Table 3.
Treatment characteristics
| Characteristic | n = 6 |
|---|---|
| Index abemaciclib line of therapy (L) | |
| 1L | 2 (33.3) |
| 3L | 1 (16.7) |
| 4L | 1 (16.7) |
| 5L | 1 (16.7) |
| 6L | 1 (16.7) |
| Number of prior lines of therapy in the metastatic setting, mean (SD) | 2.3 (2.1) |
| Prior therapy in metastatic setting | |
| Chemotherapy | 3 (50.0) |
| Hormone therapy | 4 (66.7) |
| AI | 4 (66.7) |
| Selective estrogen receptor modulators | 1 (16.7) |
| Selective estrogen receptor down-regulators | 3 (50.0) |
| Targeted and immunotherapy | 3 (50.0) |
| CDK 4&6Is | 2 (33.3) |
| Reason for discontinuation of prior CDK 4&6Is in metastatic setting | |
| Adverse event/Drug toxicity/Intolerability | 1 (16.7) |
| Disease progression | 1 (16.7) |
All data are presented as n (%), unless specified
AI aromatase inhibitor, CDK 4&6Is cyclin-dependent kinase 4/6 inhibitors, ESMO European Society for Medical Oncology, SD standard deviation
Treatment Patterns
Four of the six patients were treated with abemaciclib in combination with fulvestrant. One patient was treated with abemaciclib in combination with an AI and one patient with abemaciclib monotherapy. Abemaciclib 150 mg BID was the most common initial dose and administered to four patients; the other two patients were treated with initial doses of 50 mg BID (n = 1) and 100 mg BID (n = 1). Most patients initiated abemaciclib in or after third-line (3L) therapy (n = 4). Two patients discontinued their index abemaciclib regimen before the end of follow-up: one due to progression and the other based on physician’s choice.
Response to Treatment
Real-world best response was documented in four patients while on abemaciclib treatment. One patient each experienced CR, PR, SD, and PD. The anti-cancer response for the remaining two patients was not documented.
Discussion
The rarity of breast cancer in males (~ 1.0%) has historically led to these patients being excluded from clinical trials; as a result, treatment recommendations have largely been based on clinical experience and data generated in female patients [5]. Limited real-world evidence (RWE) studies for abemaciclib and other CDK 4&6Is make up the body of evidence for their use in males with HR+, HER2– MBC [13, 14, 19]. The current study in particular adds to this body of evidence for male patients with HR+, HER2− MBC who were treated with an abemaciclib-containing regimen [13], as previously published RWE describe results for a single patient. Information on clinical characteristics, treatment history, and response to abemaciclib-containing treatment for six patients is described here. Similar to other RWE analyses of CDK 4&6I in men [13, 14, 19], the number of male patients included in this analysis is small; however, on a percentage basis (1.8%), this aligns with the US and global prevalence of MBC in males [1, 2].
In the current study, the male patients had a high metastatic burden (4 patients with ≥ 3 metastatic sites) and a high score on the Elixhauser comorbidity index, ≥ 3 for three patients. Most patients were treated with abemaciclib + fulvestrant, and one patient each with abemaciclib + AI and abemaciclib monotherapy in/after 3L. The patients had prior treatment history with AIs, chemotherapy, and/or prior non-abemaciclib CDK 4&6Is in the metastatic setting. Despite these characteristics, three male patients in this study experienced tumor response or stabilization, with one patient each experiencing CR, PR, and SD. The patient characteristics in this study were similar to the heavy metastatic burden of patients in the real-world POLARIS study, in which males with HR+, HER2− MBC were treated with palbociclib in the 1L or 2L settings [14]. Of 15 patients, 1 experienced a real-world CR, and 4 experienced a real-world PR. The anti-cancer activity in these studies reinforce the utility of CDK 4&6Is in male patients with MBC. The National Comprehensive Cancer Network guidelines for treatment of MBC recommend CDK 4&6Is including abemaciclib in 1L in combination with an AI or fulvestrant, and in combination with fulvestrant as 2L or subsequent therapy as an additional systemic treatment option in patients with a high metastatic burden [5]. Abemaciclib monotherapy is also a treatment option in subsequent lines in patients who have received prior endocrine therapy and/or chemotherapy [5]. These recommendations are based largely on studies of women as well as published data from routine clinical practice [5, 13, 14, 19].
Historically, the treatment for male patients has been based on the clinical trials and treatment options available for female patients with MBC [5], which has led to no specific treatment guidance for males. However, the recent FDA guidance for developing drugs for breast cancer in males recommends including both females and males in clinical trials of breast cancer drugs. Furthermore, clinical trial findings from the female population may be extrapolated to male patients when males have not been included or the number of males included in the trial is small. The guidance also recommends that sponsors conduct non-clinical general toxicology studies in male and female animals when they have included male patients in clinical trials of breast cancer drugs. This guidance for drug manufacturers will hopefully lead to increased participation of male patients in breast cancer trials and, hence, a more patient-centric approach for male patients with breast cancer [20]. Abemaciclib is FDA-approved in combination with endocrine therapy for male patients with early breast cancer and MBC, and as monotherapy in male patients with MBC [15].
This study has certain limitations. The number of patients in this analysis is small; however, the overall prevalence of males with MBC in the present study is consistent with the prevalence in the overall population, and provides additional real-world data for male patients with HR+, HER2− MBC treated with abemaciclib. Second, data are presented in aggregate to maintain patient confidentiality of patients in this small cohort; therefore, patient characteristics cannot be linked to results for individual patients. Additionally, we have used the term “anti-cancer activity”, instead of “effective or effectiveness”, to not overstate the results presented here. In addition, the start date of this study coincides approximately with abemaciclib approval in 2017. Future analyses are warranted to determine if observations documented here persist over time.
Conclusions
Abemaciclib-containing regimens were initiated in ≥ 3L in most patients in this study, and showed anti-cancer activity despite endocrine resistance status, heavy metastatic burden, non-cancer comorbidity burden, and prior treatments for metastatic disease. These data provide additional evidence for male patients treated with abemaciclib for HR+, HER2− MBC in a community oncology setting.
Acknowledgements
Funding
This study was performed under a research contract between Xcenda LLC and Eli Lilly and Company and was funded by Eli Lilly and Company. Publication for this study, including the journal's Rapid Service and Open Access Fees, was also funded by Eli Lilly and Company.
Medical Writing/Editorial Assistance
The authors would like to thank Karan Sharma from Eli Lilly Services India Pvt. Ltd. (funded by Eli Lilly and Company) for providing medical writing and editorial support.
Author Contributions
Conception of work: Emily Nash Smyth, Tasneem Lokhandwala, Sarah Rybowski. Design of the work: Emily Nash Smyth, Tasneem Lokhandwala, Joanne Willey, Zhanglin Lin Cui. Data acquisition: Tasneem Lokhandwala, Orsolya Lunacsek, Joanne Willey. Data analysis: Joanne Willey, Orsolya Lunacsek. Data interpretation: Alistair Ring, Meghan Karuturi, Emily Nash Smyth, Tasneem Lokhandwala, Kristin M. Sheffield, Joanne Willey, Orsolya Lunacsek, Francisco Sapunar, Zhanglin Lin Cui, Anna Coutinho, Sarah Rybowski. Manuscript writing and critical revision: Alistair Ring, Meghan Karuturi, Emily Nash Smyth, Tasneem Lokhandwala, Kristin M. Sheffield, Joanne Willey, Orsolya Lunacsek, Francisco Sapunar, Zhanglin Lin Cui, Anna Coutinho, Sarah Rybowski. Final approval: Alistair Ring, Meghan Karuturi, Emily Nash Smyth, Tasneem Lokhandwala, Kristin M. Sheffield, Joanne Willey, Orsolya Lunacsek, Francisco Sapunar, Zhanglin Lin Cui, Anna Coutinho, Sarah Rybowski.
Disclosures
Alistair Ring – Employment: The Royal Marsden NHS Foundation Trust, London, UK. Consulting Fee: Eli Lilly and Company; Non-CME Services Fee: Eli Lilly and Company, Novartis, and Pfizer; Other: Eli Lilly and Company and Novartis; Honoraria for advisory boards: Daiichi-Sankyo, Roche, Stemline, Seagen, Gilead, Novartis, Eli Lilly and Company; CME: Eli Lilly and Company and Pfizer. Meghan Karuturi – Employment: MD Anderson Cancer Center, Houston, Texas, US; Consulting Fee: Eli Lilly and Company and Pfizer. Emily Nash Smyth, Kristin M. Sheffield, Francisco Sapunar, Zhanglin Lin Cui, and Sarah Rybowski are employees and stockholders at Eli Lilly and Company. Tasneem Lokhandwala, and Joanne Willey, are employees at Xcenda LLC. Anna Coutinho* and Orsolya Lunacsek* are former employees at Xcenda LLC and were associated with Xcenda LLC at the time of study completion and manuscript writing. Anna’s current affiliation is GlaxoSmithKline, US VEO. Orsolya’s current affiliation is Bayer AG.
Compliance with Ethics Guidelines
There was no overlap or duplication of available patient data from the two databases (Florida Cancer Specialists & Research Institute [FCS] and Electronic Medical Office Logistics [EMOL] Health Oncology Warehouse Language [OWL]™), and the study was approved with a waiver of consent and a full waiver of Health Insurance Portability and Accountability Act authorization by the Advarra Institutional Review Board.
Data Availability
The datasets generated during and/or analyzed during the current study are not publicly available in order to i) maintain confidentiality of the small cohort of patients and the ii) contract between Xcenda and Eli Lilly and Company did not include the sharing of the analytical file.
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Associated Data
This section collects any data citations, data availability statements, or supplementary materials included in this article.
Data Availability Statement
The datasets generated during and/or analyzed during the current study are not publicly available in order to i) maintain confidentiality of the small cohort of patients and the ii) contract between Xcenda and Eli Lilly and Company did not include the sharing of the analytical file.