Clinical Implications of the Serum CA19-9 Level in "biological Borderline Resectability" and "biological Downstaging" in the Setting of Preoperative Chemoradiation Therapy for Pancreatic Cancer

Background: Biological factors are emphasized in borderline resectable pancreatic cancer (BRPC), and CA19-9 is an important factor for biological borderline resectability (b-BR). The aim of this study was to investigate the cut-off value of CA19-9 for biological borderline resectability and "biological downstaging" in chemoradiation therapy (CRT) for pancreatic cancer (PC).

Methods: A total of 407 patients with anatomically resectable PC (a-R) and BRPC (a-BR) received preoperative gemcitabine-based CRT. The b-BR was determined, according to the CA19-9 value prior to preoperative CRT (pre-CA19-9), as the subgroup of a-R cases in which the survival was comparable with that in a-BR cases. "Biological downstaging" was determined based on prognostic analyses regarding the CA19-9 value after preoperative CRT (post-CA19-9) in association with the survival of R cases (a-R cases without the b-BR factor).

Results: The 5-year survival of a-R patients with pre-CA19-9 > 120 U/mL was comparable with that of a-BR patients (44% vs 34%, p = 0.082). The survival of b-BR patients with post-CRT CA19-9 ≤ 37 U/mL (normalized) was comparably favorable with that of R patients (56% vs 65%, p = 0.369). The incidence of distant recurrence was higher in b-BR patients without post-CA19-9 normalization than in those with post-CA19-9 normalization (70% vs 50%, p = 0.003), while the incidence of local recurrence was comparable between these two groups (12% vs 13%, p = 0.986).

Conclusions: Biological BRPC was determined to be an anatomically resectable disease with pre-CA19-9 > 120 U/mL, and post-CA19-9 normalization indicated "biological downstaging" in b-BR in the preoperative CRT strategy.