Impact of histological response after neoadjuvant chemoradiotherapy on recurrence-free survival in UICC-T3 pancreatic adenocarcinoma but not in UICC-T4

Objectives: Although the prognostic benefit of neoadjuvant chemoradiotherapy (NCRT) against pancreatic cancer has been indicated by several reports, it is controversial whether histological response is associated with prognosis. The objective was to explore the relationship between histological response and prognosis in T3 and T4 pancreatic adenocarcinoma. Methods: We histologically examined the resected specimens obtained from 58 patients (T3, n = 40; and T4, n = 18) for whom we performed curative-intent resection after NCRT. Histological response was evaluated according to Evans's criteria to determine whether it influenced survival. Results: In T3 tumors, 13 (32.5%) belonged to high responders (tumor destruction of >50%) (R0, n = 13) and 27 (67.5%) belonged to low responders (tumor destruction of ≤50%) (R0, n = 22, R1, n = 3, R2, n = 2). Recurrence-free survival rate was significantly higher in high responders than in low responders (3-year recurrence-free survival rates: 71.3% vs 13.1%, P = 0.0095). In T4 tumors, however, only 1 (5.6%) was a high responder, and R0 resection was obtained only in 5 patients (27.8%). Conclusions: In T3 tumors, histological response is considered a significant prognostic indicator, securing the surgical margin, whereas in T4 tumors, NCRT did not provide beneficial histological response, not securing the surgical margin.