Chemotherapy-induced early transient increase and surge of CA 19-9 level in patients with pancreatic Adenocarcinoma✰.

This study aimed to characterize chemotherapy-induced transient increase and surge of CA 19-9 level to treatment response in patients with advanced pancreatic ductal adenocarcinoma (PDAC). A retrospective case series was performed of advanced PDAC patients treated with first-line chemotherapy at City of Hope Comprehensive Cancer Center from Jan 2017 to May 2020. CA 19-9 surge was defined as an increase of >20% from baseline followed by a >20% drop in one or more subsequent CA 19-9 levels compared to baseline. Out of 106 advanced PDAC patients, 38 were evaluable for CA 19-9 surge. Fourteen (51.9%) patients treated with FOLFIRINOX and 3 (27.3%) patients treated with nab-P + Gem chemotherapy demonstrated an early transient rise in CA 19-9 level. A CA 19-9 surge was documented in 9 (23.7%) patients, all with duration of surge lasting < 16 weeks. Five out of 9 (55.6%) patients (4: FOLFIRINOX, 1: nab-P + Gem) with CA 19-9 surge demonstrated partial objective response rate on surveillance cross-sectional imaging. One patient (FOLFIRINOX) had stable disease, and 2 patients (1: FOLFIRINOX, 1: nab-P + Gem) were found to have disease progression after treatment interruption. The initial early rise of CA 19-9 levels during chemotherapy in patients with advanced PDAC may not indicate tumor progression. Rather, it may represent a chemotherapy-induced transient increase or surge phenomenon of the tumor marker in patients responding to treatment.