Comparison of radiological and pathological tools to assess response to neoadjuvant treatment in resected pancreatic ductal adenocarcinoma patients.

Background: In non-metastatic pancreatic adenocarcinoma (PDAC), the appropriate evaluation of tumor response to neoadjuvant treatment (NAT) has a substantial prognostic impact, but the tools used to assess it are imperfect and sometimes discordant. Objectives: We aimed to explore the prognostic impact of morphological and pathological evaluations of tumor response to NAT. Design: Single-center retrospective observational study. Methods: We retrospectively studied all patients with borderline or locally advanced PDAC who underwent surgery after neoadjuvant chemotherapy (NAC) with FOLFIRINOX, ±additional chemoradiation (NACR) between 2016 and 2022 in a tertiary center. Morphological response was evaluated according to RECIST 1.1, and pathological response was assessed according to the CAP score and proportion of viable tumor cells (VTC). The primary endpoint was recurrence-free survival (RFS), and the secondary endpoint was overall survival (OS). Factors associated with the risk of recurrence were analyzed using ROC curves and multivariable Cox proportional hazard models. Results: We included 91 patients (52% male, median age 66, 83% with borderline PDAC) who underwent surgery following NAC with additional NACR in 85% of patients. Overall, 38% of patients had an objective morphological response according to RECIST 1.1, which was not associated with prolonged RFS HR 1.16, 95% CI (0.62-2.10), p = 0.64). Conversely, poor pathological response was associated with shorter RFS on multivariable analysis, notably VTC ⩾ 30% (HR 2.28, 95% CI [1.08-5.13], p = 0.037). Median OS was 62.2 months with VTC ⩾ 30% versus 45.1 months with VTC < 30% (p = 0.025). Identifying PDAC with VTC < or ⩾30% had a strong reproducibility (kappa 0.86). Conclusion: Morphological response per RECIST should not be the aim of NAT in patients with PDAC. Conversely, the proportion of VTC could be a reproducible, simple, and effective prognostic tool. Should this marker be further confirmed as valuable, it may help inform the adaptation of adjuvant treatment and follow-up in this setting.