The 30% reduction of baseline CA19-9 could stratify the prognosis of advanced pancreatic ductal adenocarcinoma with RECIST stable disease after first-line chemotherapy

Abstract

Background

Radiological assessment based on RECIST criteria has limited accuracy in evaluating chemotherapy response in advanced pancreatic ductal adenocarcinoma (PDAC), particularly in patients classified as stable disease. Additional clinically accessible biomarkers are needed to better stratify treatment response and prognosis in this population.

Methods

This study retrospectively included patients with advanced PDAC who received first-line chemotherapy and completed an 8-week response assessment. Contrast-enhanced CT and serum CA19-9 were evaluated every 8 weeks for disease surveillance. The primary endpoints were progression-free survival (PFS) and overall survival (OS).

Results

Of 182 patients included, 117 (64.3%), 21 (11.5%), and 44 (24.2%) patients were classified into SD, partial response (PR), and progressive disease (PD) at the first radiological evaluation. The SD cohorts presented OS similar to the PR cohort (P = 0.348). In SD patients with elevated baseline CA19-9 levels, the cohort with a 30% reduction of baseline CA19-9 levels was defined as the CA19-9 response group. Compared with the nonresponse group (decreased < 30% or increased CA19-9 cohorts), the response group presented significantly better PFS (P < 0.001) and OS (P = 0.010).

Conclusions

After 8 weeks of first-line chemotherapy, most patients with advanced PDAC were classified as SD and exhibited survival outcomes comparable to those with partial response. In patients with stable disease and elevated baseline CA19-9 levels, a ≥ 30% reduction in CA19-9 provided additional prognostic stratification.

Supplementary Information

The online version contains supplementary material available at https://doi.org/10.1186/s12885-026-16353-z.

Introduction

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal and challenging malignancies in the field of oncology, with a 5-year overall survival (OS) of around 10% [1]. Most PDAC patients present with locally advanced tumors or distant metastasis at diagnosis, with only a minority being eligible for curative surgery [2]. Systemic chemotherapy remains a crucial intervention to improve the prognosis for advanced PDAC. Currently, AG (nab-paclitaxel plus gemcitabine) and FOLFIRINOX (fluorouracil, leucovorin, irinotecan, and oxaliplatin) regimens are recommended as first-line chemotherapy options [3]. However, chemotherapy resistance restricts the oncological benefits of first-line chemotherapy for PDAC [4]. Therefore, it is essential to accurate assessment of chemotherapy response for early clinical reassessment and decision-making.

The Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 is recommended for response evaluation in most solid tumors including PDAC, which classifies patients into complete response (CR), partial response (PR), stable disease (SD), and progressive disease (PD) [5]. Nevertheless, previous studies have reported the limitations of RECIST in assessing treatment response in pancreatic cancer; patients with stable disease presented great heterogeneity in prognosis [6, 7]. Given the limited accuracy of RECIST-based imaging assessment in PDAC, particularly among patients classified as stable disease, reliance on radiographic criteria alone may delay identification of patients who derive insufficient benefit from ongoing chemotherapy, thereby postponing clinical reassessment and potentially exposing patients to continued toxicity without meaningful benefit. Previous research tried to evaluate chemotherapy response using tumor metabolic volume, sequencing data, and radiomic features, but the clinical accessibility remains limited [8–10]. Serum carbohydrate antigen 19 − 9 (CA19-9) is acknowledged as an effective biomarker for reflecting the biological activity of PDAC, which could effectively assess the therapeutic response, long-term prognosis, and surgical resectability [11–13]. Here, we hypothesized that monitoring CA199 levels during peri-chemotherapy could accurately stratify chemotherapy response in advanced PDAC patients with SD.

This study aims to assess whether CA19-9 dynamics could complement RECIST and enhance the evaluation of chemotherapy response after first-line chemotherapy in advanced PDAC.

Method

Definitions of the study

The first-line chemotherapy regimen includes gemcitabine-based systemic therapy and modified (m) FOLFIRINOX was performed according to the guidelines after comprehensive estimation by multi-disciplinary teams [3, 14]. In this cohort, gemcitabine-based systemic therapy primarily consisted of the AG regime. The AG regimen consisted of nab-paclitaxel at 125 mg/m² administered by intravenous infusion on days 1 and 8, and gemcitabine at 1,000 mg/m² administered by intravenous infusion on days 1 and 8, repeated every 3 weeks. FOLFIRINOX was consisted of oxaliplatin 85 mg/m² (intravenous infusion, day 1), irinotecan 180 mg/m² (intravenous infusion, day 1), leucovorin 400 mg/m² (intravenous infusion, day 1), followed by 5-fluorouracil (5-FU) 400 mg/m² as an intravenous bolus on day 1 and then 5-FU 2,400 mg/m² as a continuous intravenous infusion over 46 h, repeated every 2 weeks. (m) FOLFIRINOX was consisted of oxaliplatin 85 mg/m² (intravenous infusion, day 1), irinotecan 150 mg/m² (intravenous infusion, day 1), leucovorin 400 mg/m² (intravenous infusion, day 1), followed by 5-FU 2,400 mg/m² as a continuous intravenous infusion over 46 h, repeated every 2 weeks. Each patient who receives chemotherapy undergoes an abdominal radiological examination and CA19-9 assessment every eight weeks to evaluate the chemotherapy response. Serum CA19-9 levels were measured using an enzyme-linked immunosorbent assay (ELISA). A CA19-9 level greater than 37 U/mL was considered abnormally elevated in our center. RECIST 1.1 was used to evaluate the radiologic disease response on CT imaging after 8 weeks of chemotherapy. We attempted to evaluate chemotherapy response by comparing the dynamics of CA19-9 levels and quantifying the change from baseline. Therefore, serum CA19-9 was collected before the first course of chemotherapy and after 8 weeks of chemotherapy. The American Joint Committee on Cancer (AJCC) TNM staging system was used to determine the tumor stage of PDAC. The primary outcome of this study was the overall survival (OS) and progression-free survival (PFS). OS was calculated from the date of the first course of chemotherapy to the date of the last follow-up or death. PFS was defined as the time from the first course of chemotherapy until disease progression or death from any cause. All patients after the first course of chemotherapy were routinely followed up.

Patients selection

We conducted a single-center retrospective research at the First Affiliated Hospital of Sun Yat-sen University, all consecutive patients who pathologically confirmed PDAC between January 2015 and August 2022 were included. Patients were included as the following criteria. The inclusion criterion was as follows: (i) patients were diagnosed as unresectable PDAC including PDAC with distant metastasis and locally advanced PDAC; (ii) patients who received > 4 cycles (m)FOLFIRINOX or > 2 cycles gemcitabine-based chemotherapy; (iii) the complete information of CT and CA 19 − 9 levels at baseline and at 8 weeks after initial therapy. The exclusion criteria were as follows: (i) accompanied by other concurrent malignancies; (ii) incomplete clinicopathological data and follow-up data; (iii) insufficient chemotherapy cycles received. The Ethics Committee of the First Affiliated Hospital of Sun Yat-sen University approved this study.

Data collection and statistical analysis

Clinicopathological information was collected from the retrospective database, including age at diagnosis, sex, tumor size, tumor location, CA19-9 level, tumor stage, chemotherapy regime, and follow-up information. Due to the potential impact of obstructive jaundice for abnormal CA19-9 levels, the serum bilirubin levels were assured to the normal level (< 17 µmol/L) before the CA19-9 level measurement; patients who did not achieve a normal bilirubin level were excluded [15]. Statistical analyses were conducted with R 4.0.0 (http://www.Rproject.org). Continuous data were reported as medians with interquartile (IQR), and were compared using Mann–Whitney U tests. Categorical parameters were presented as frequencies and percentages and were compared through chi square test or Fisher’s exact test. Kaplan–Meier curve and log-rank test were performed to compare the long-term survival. A two-tailed P value less than 0.05 was considered significantly different.

Results

Patients’ characteristics

A total of 182 patients who received palliative first-line chemotherapy for advanced PDAC were included. Of included patients, 110 patients (60.4%) were males and 72 patients (39.6%) were females, with a median age of 58 years (range from 51 to 65 years). The clinicopathological features of the included patients were presented in Table 1. Twenty-two (12.1%) patients received (m) FOLFIRINOX treatment and most patients received gemcitabine-based chemotherapy (n = 160, 87.9%). After the normalized serum bilirubin levels were assured, the median CA19-9 values at baseline and post-chemotherapy were 705.8 U/mL (IQR 71.9-3022.5) and 193 U/mL (IQR 48.8-2552.4). At baseline, CA19-9 levels were found to be elevated in 155 patients (85.2%), and 27 (14.84%) patients presented normal CA19-9 levels. After 8 weeks of treatment, serum CA19-9 levels decreased from baseline in 100 patients (54.9%), whereas 82 patients showed an increase (45.1%). The median follow-up months were 17.0 (14.4–19.6), and the median PFS and OS of all 182 patients were 8.0 (6.2-9.0) and 15.0 (12.8–17.2), respectively.

Table 1.

Clinicopathological features of patients with advanced PDAC

Features	Total (n = 182)
Age, years, median (IQR)	58(51–65)
Sex, n (%)
Female	72 (39.6)
Male	110 (60.4)
ECOG score, n (%)
≤ 1	174(95.6)
> 1	8(4.4)
Chemotherapy Regime, n (%)
FOLFIRINOX or modified FOLFIRINOX	22 (12.1)
Gemcitabine-based	160 (87.9)
Tumor location, n (%)
Head	80 (44.0)
Body or tail	102 (56.0)
Tumor size, mm, median (IQR)	38.0 (32.0–49.0)
Tumor size, n (%)
≤40 mm	101 (55.5)
>40 mm	81 (44.5)
AJCC T group, n (%)
T1	2 (1.1)
T2	36 (19.8)
T3	28 (15.4)
T4	116 (63.7)
Distant metastasis n (%)
No	94 (51.7)
Yes	88 (48.3)
AJCC, TNM stage, n (%)
III	94 (51.6)
IV	88 (48.4)
CA 19 − 9 at baseline, U/ml, median (IQR)	705.8 (71.9-3022.5)
CA 19 − 9 after therapy, U/ml, median (IQR)	446.6 (48.8-2552.4)
Baseline CA19-9, n (%)
Elevate (> 37 U/ml)	155 (85.2)
Normal (≤ 37 U/ml)	27 (14.8)
Dynamic of CA19-9 from baseline, n (%)
Down	100 (54.9)
Up	82 (45.1)
RECIST1.1, n (%)
PD	44 (24.2)
PR	21 (11.5)
SD	117 (64.3)
Median overall survival (m), median (95%CI)	15.0 (12.8–17.2)
Median follow-up time (m), median (95%CI)	17.0 (14.4–19.6)

Abbreviations: PDAC Pancreatic ductal adenocarcinoma, IQR Interquartile range, ECOG Eastern Cooperative Oncology Group, FOLFIRINOX Fluorouracil, leucovorin, irinotecan, and oxaliplatin, AJCC American Joint Committee on Cancer, CA 19 − 9 Carbohydrate antigen 19 − 9, RECIST Response Evaluation Criteria in Solid Tumors, PD Progressive disease, PR Partial response, SD Stable disease

Survival analysis of the whole cohort

Univariable Cox analysis showed that AJCC TNM stage (HR 1.49, 95% CI 1.04–2.14; P = 0.028) and the increase of post-therapy CA19-9 level (HR 1.88, 95% CI 1.31–2.70; P < 0.001) were significant prognostic factors for PFS (Supplementary Table S1). We also conducted the Cox regression analyses for OS in advanced PDAC. The AJCC TNM stage, the increase of post-therapy CA19-9 level, and RECIST 1.1 response category were significantly associated with OS (Supplementary Table S2). According to the RECIST 1.1, 117 (64.3%), 21 (11.5%), and 44 (24.2%) patients were classified into SD, PR, and PD after 8-week chemotherapy, respectively (Fig. 1A). No patients were found CR after 8 weeks of chemotherapy. The SD and PR cohorts all presented significantly better OS compared with the PD cohorts (P = 0.004 and P < 0.001) according to the KM curve for OS. However, no significant prognosis difference was observed between the SD and PR cohorts (P = 0.348) (Fig. 1B).

Fig. 1.

The performance of the RECIST in evaluating the chemotherapy response. A Kaplan–Meier survival curve based on the CT response for advanced PDAC after 8 weeks of chemotherapy. B The proportion of patients based on the RECIST after 8 weeks of chemotherapy

The prognosis of the reduction of CA19-9 in SD patients

Of 117 patients with SD after 8-week chemotherapy, elevated CA19-9 levels were found in 98 (83.8%) patients at baseline. The median PFS of these patients was 10.0 (8.8–11.2), and the median OS was 17.0 (13.7–20.3) months. The optimal cut-off values were determined based on the long-term prognosis of advanced PDAC (Table 2). Patients were categorized according to post-chemotherapy CA19-9 dynamics. A ≥ 30% decrease in CA19-9 from baseline defined the CA19-9 response group; a < 30% decrease or any increase defined the CA19-9 nonresponse group.

Table 2.

The optimal cutoff of CA19-9 for the prognosis of advanced PDAC

Variables	Patients Number	Progression-free survival	Overall survival
		Median PFS (months; 95% CI)	P value	Median OS (months; 95% CI)	P value
CA19-9			0.220		0.970
Normalized	15	13.0 (8.3–17.7)		17.0 (5.9–28.1)
Non-normalized	83	9.0 (7.9–10.1)		17.0 (13.2–20.8)
10% cutoff			< 0.001		0.059
No	27	6.0 (4.3–7.5)		13.0 (7.6–18.4)
Yes	71	11.0 (9.2–12.8)		17.0 (9.5–24.5)
20% cutoff			0.099		0.049
No	29	9.0 (7.6–10.4)		14.0 (11.3–16.7)
Yes	69	10.0 (7.9–12.1)		17.0 (7.3–26.7)
30% cutoff			< 0.001		0.010
No	38	5.0 (3.2–6.9)		13.0 (7.5–18.5)
Yes	60	11.0 (9.2–12.8)		17.0 (9.5–24.5)
40% cutoff			0.084		0.368
No	47	8.0 (5.7–10.3)		16.0 (11.8–20.2)
Yes	51	11.0 (8.6–13.4)		18.0 (10.1–25.9)
50% cutoff			0.074		0.263
No	52	9.0 (7.3–10.6)		14.0 (11.0–17.0)
Yes	46	12.0 (8.3–15.7)		22.0 (13.6–30.4)
60% cutoff			0.080		0.137
No	60	9.0 (7.3–10.7)		14.0 (11.4–16.6)
Yes	38	11.0 (4.9–17.1)		22.0 (14.6–29.4)
70% cutoff			0.178		0.240
No	72	9.0 (7.8–10.2)		15.0 (12.7–17.3)
Yes	26	12.0 (6.7–17.3)		23.0 (14.4–31.6)
80% cutoff			0.237		0.395
No	79	9.0 (7.8–10.2)		15.0 (12.6–17.5)
Yes	19	14.0 (5.2–22.8)		23.0 (11.1–34.9)
90% cutoff			0.930		0.648
No	90	10.0 (8.8–11.2)		17.0 (14.2–19.8)
Yes	8	8.0 (4.0-26.2)		24.0 (8.0–40.0)

Values in parentheses are 95% confidence intervals

Abbreviations: PDAC Pancreatic ductal adenocarcinoma, PFS Progression-free survival, OS Overall survival, CA 19 − 9 Carbohydrate antigen

From the K-M curve, the response group presented significantly better PFS (5.0 months vs. 11.0 months, P < 0.001) and OS (13.0 months vs. 17.0 months, P = 0.010) compared with the nonresponse group (Fig. 2). The Cox analysis was conducted to verify the prognosis values of CA19-9 in these patients (Table 3). The CA19-9 response was the sole prognosis factor for PFS (HR 0.35, 95% CI: 0.21–0.60, P < 0.001) and OS (HR 0.45, 95% CI: 0.24–0.85, P = 0.014). Representative patients of the CA19-9 response group and the CA19-9 nonresponse group were shown in Fig. 3. Nevertheless, other conventional parameters including age, sex, tumor size, tumor location, AJCC TNM stage, and chemotherapy regime were not significantly associated with PFS and OS.

Fig. 2.

Kaplan–Meier curve shows the performance of the CA19-9 response in stratifying the long-term prognosis of advanced PDAC with SD. A Kaplan–Meier curve analysis for PFS based on the CA19-9 response. B Kaplan–Meier curve analysis for OS based on the CA19-9 response

Table 3.

Univariable Cox analyses for the long-term prognosis of advanced PDAC

Variables	Progression-free survival		Overall survival
	HR (95%CI)	P value	HR (95%CI)	P value
Age (years)	0.99 (0.97 ~ 1.02)	0.600	0.99 (0.96 ~ 1.02)	0.616
Sex
Female	Reference		Reference
Male	1.01 (0.62 ~ 1.65)	0.957	0.93 (0.52 ~ 1.67)	0.817
Tumor location
Body or tail	Reference		Reference
Head	1.10 (0.68 ~ 1.78)	0.685	1.42 (0.79 ~ 2.54)	0.238
Tumor size
≤ 4 cm	Reference		Reference
> 4 cm	0.99 (0.61 ~ 1.61)	0.960	1.02 (0.56 ~ 1.87)	0.945
AJCC T stage
T1-T2	Reference		Reference
T3-T4	0.98 (0.56 ~ 1.71)	0.946	0.88 (0.46 ~ 1.67)	0.688
Multiple organ metastasis
No	Reference		Reference
Yes	1.24 (0.77 ~ 2.01)	0.371	1.11 (0.62 ~ 1.97)	0.730
Chemotherapy regime
(m) FOLFIRINOX	Reference		Reference
Gemcitabine-based	0.89 (0.40 ~ 1.94)	0.762	0.71 (0.32 ~ 1.60)	0.408
CA199 Response
Nonresponse	Reference		Reference
Response	0.35 (0.21 ~ 0.60)	< 0.001	0.45 (0.24 ~ 0.85)	0.014

Abbreviations: PDAC Pancreatic ductal adenocarcinoma, FOLFIRINOX Fluorouracil, leucovorin, irinotecan, and oxaliplatin, AJCC American Joint Committee on Cancer, CA 19 − 9 Carbohydrate antigen

Fig. 3.

Representative patients of the CA19-9 response group and the CA19-9 nonresponse group. A case of a 59-year-old man with pancreatic ductal adenocarcinoma (PDAC), who received nab-paclitaxel plus gemcitabine (AG) for chemotherapy. A The baseline contrast-enhanced axial CT image shows a 32-mm tumor at the pancreatic head, which was regarded as unresectable PDAC. B After 8 weeks of chemotherapy of AG, the contrast-enhanced axial CT image shows the size of the tumor slightly increased (35 mm), classified as stable disease (SD) as RECIST criteria. The AG regime was continued for this patient. The baseline CA19-9 level of this patient was 177.67 U/mL. Following eight weeks of AG chemotherapy, the CA19-9 level decreased to 57 U/mL, reducing more than 30%. This patient experienced tumor progression after 12 months of chemotherapy and ultimately survived for more than 24 months. Another case was a 55-year-old man with PDAC, who also received AG for chemotherapy. C The baseline contrast-enhanced axial CT image shows a 38-mm tumor at the pancreatic head. D The contrast-enhanced axial CT image after 8-week chemotherapy shows the tumor size slightly decreased, classified as SD as RECIST criteria, and the AG regime was continued. The baseline CA19-9 level of this patient was 3624.75 U/mL. The CA19-9 level decreased to 3468.18 U/mL following eight weeks of chemotherapy, reducing less than 30%. This patient experienced tumor progression after 6 months of chemotherapy and ultimately survived only 11 months

Discussion

Early assessment of tumor response to chemotherapy and subsequent adjustment of chemotherapeutic regimes are crucial for improving clinical outcomes in PDAC treatment. This study found that relying solely on the RECIST was insufficient for accurately assessing the efficacy of chemotherapy in advanced PDAC. In our study, the majority of patients (n = 117, 64.3%) were classified as SD after 8 weeks of first-line chemotherapy, which presented a similar prognosis to the PR cohorts. Specifically, in SD patients with abnormal baseline CA19-9 (n = 98, 83.8%), the cohort who achieved a ≥ 30% reduction in CA19-9 from baseline experienced significantly improved survival outcomes. Monitoring the dynamics of serum CA19-9 could help further stratify the prognosis in these patients, which helps guide clinical decision-making.

The limitations of the RECIST in assessing the chemotherapeutic response of PDAC have been frequently reported. The primary tumors of PDAC are characterized by abundant fibrosis, which therefore appear as hypovascular tumors [16, 17]. On the other hand, the chemotherapy for PDAC also induces a dense fibrotic reaction, which cannot be distinguished from the fibrosis of residual tumors in radiology [18, 19]. The slight alternations of tumor size caused by the chemotherapy-induced fibrosis affect the accuracy of RECIST in evaluating the chemotherapy response for PDAC. Therefore, most patients are classified as SD at the initial imaging assessment, negatively impacting the treatment strategies. To our knowledge, only one study has attempted to further stratify the prognosis of PDAC with SD based on the radiomics features, but the relatively poor clinical accessibility restricts the clinical value [20]. In this study, we found that conventional clinicopathological parameters like age, sex, tumor location, and size weren’t significantly associated with the prognoses of patients with SD. By monitoring the dynamics of peri-chemotherapy CA19-9, we could effectively stratify the prognosis for these patients.

Serum CA19-9 is the most widely used biomarker for disease monitoring and treatment response assessment in PDAC. The National Comprehensive Cancer Network (NCCN) guidelines incorporate CA19-9 into the longitudinal management of PDAC, and CA19-9 levels are commonly considered alongside imaging when clinicians evaluate disease extent and treatment planning [3]. Abundant evidence supports elevated baseline CA19-9 as an independent adverse prognostic factor, reflecting more advanced tumor biology and higher tumor burden [21]. Importantly, in the potentially resectable preoperative CA19-9 has been associated with a higher likelihood of occult metastatic disease or local unresectability [22]. As a treatment-response marker, the prediction for differential benefit across regimens remains uncertain, and randomized evidence for baseline CA19-9 as a true predictive biomarker is limited [22]. Many studies have shown that dynamic changes in CA19-9 levels after treatment may better reflect treatment efficacy than a single baseline measurement. Previous studies demonstrated that the reduction or normalization of CA19-9 baseline levels could reflect the chemotherapeutic efficacy [23–25]. A multicenter retrospective study indicated that CA19-9 decreases > 60% baseline levels could predict the prognosis of induction chemotherapy for locally advanced PDAC [15]. However, relying solely on dynamic changes in CA19-9 to guide clinical decision-making is generally insufficient. Few studies combined the CA19-9 and radiological images to evaluate the chemotherapy response in advanced PDAC. Our study aimed to enhance the precision of evaluating chemotherapy response by complementing radiological response with CA19-9 monitoring. A ≥ 30% reduction in CA19-9 from baseline may help more accurately evaluate chemotherapy response and stratify prognosis among patients with advanced PDAC who are classified as SD. Based on our findings, the detection of CA19-9 levels and CT during chemotherapy for advanced PDAC was strongly recommended. The following recommendations were given according to the radiological images and CA19-9 response. The current chemotherapy regimen could be continued for PR cohorts but wasn’t recommended for PD cohorts. Especially for SD patients with elevated CA19-9 baseline levels, the initial chemotherapy regimen could be maintained for CA19-9 response cohorts. The adjustment of the chemotherapy regimen should be considered in the CA19-9 nonresponse group (Fig. 4).

Fig. 4.

The flowchart of the recommendation based on the radiological response and CA19-9 response

Several limitations should be noted in this study. Our research was mainly aimed at patients with abnormal baseline CA19-9, and the subgroup analysis wasn’t conducted due to the small sample size. Although the proportions of the cohorts with normal CA19-9 levels in PDAC were relatively small [26]. In this study, data on subsequent (second-line) treatments were not systematically collected. Although these post-progression therapies typically do not affect PFS, they may substantially influence OS and therefore represent an important limitation of our analysis. And this study was a single-center retrospective study, the cut-off for CA19-9 reduction (≥ 30% from baseline) was defined in a post-hoc manner based on its association with survival outcomes. Prospective research from multiple centers is required to verify the effectiveness of the recommendations.

Conclusion

After 8 weeks of first-line chemotherapy, most patients with advanced PDAC were classified as SD and exhibited survival outcomes comparable to those with partial response. In patients with stable disease and elevated baseline CA19-9 levels, a ≥ 30% reduction in CA19-9 provided additional prognostic stratification.

Abbreviations

AG

Nab-paclitaxel plus gemcitabine

AJCC

The American Joint Committee on Cancer

CA19-9

Carbohydrate antigen 19 − 9

CR

Complete response

FOLFIRINOX

Fluorouracil, leucovorin, irinotecan, and oxaliplatin

IQR

Interquartile

NCCN

National Comprehensive Cancer Network

OS

Overall survival

PD

Progressive disease

PDAC

Pancreatic ductal adenocarcinoma

PFS

Progression-free survival

PR

Partial response

RECIST

Response Evaluation Criteria in Solid Tumors

SD

Stable disease

Authors’ contributions

Protocol/project development: Yin; Data collection or management: Zhang, Fu, Xi-Tai Huang, Liang; Data analysis: Chen-song Huang, Xu, Cai, Lai; Manuscript writing/editing: Zhang, Xi-Tai Huang, Fu; Manuscript review: Yin. All authors read and approved the submitted version.

Funding

This work was supported by grants from the Guangzhou Science and Technology Plan Project (No. 2023A04J2211) and the National Natural Science Foundation of China (No. 82203105).

Data availability

The datasets generated in this study are available on request from the corresponding author.

Declarations

Ethics approval and consent to participate

The research protocol was approved by the Institutional Ethical Review Boards of the First Affiliated Hospital of Sun Yat-sen University in accordance with the declaration of Helsinki (Approved ID: IIT-2024-582).The need for written informed consent was waived by the Ethical Committee of the First Affiliated Hospital of Sun Yat-sen University due to the retrospective nature of the study.

Consent for publication

Not applicable.

Competing interests

The authors declare no competing interests.