Changes in peri-operative chemotherapy and radiation use among patients with resected pancreatic ductal adenocarcinoma (PDAC) between 2004-2021 in the US SEER dataset.

697 Background: PDAC peri-operative management changed over 20 years. Randomized data supports adjuvant and multiagent chemotherapy (CT), while peri-operative chemoradiotherapy (RT) was used selectively in the US. We examined recent trends in treatment with outcomes in surgically resected PDAC patients. Methods: Using the Surveillance, Epidemiology, and End Results (SEER) 17 dataset, we identified surgically resected primary M0/MX PDAC cases from 2004-2021 over 3-year periods (P1-P6). Neoadjuvant (NCT), adjuvant (ACT), or multiagent (MACT) CT scheduling was included. χ² analysis assessed cohort characteristics over time and multinomial logistic regression assessed odds of CT allocation adjusted by cohort characteristics. Multivariable Cox proportional hazards model assessed treatment-related overall survival (OS) adjusted for cohort characteristics. Results: Among 55,293 cases of M0/MX PDAC, 21,904 (40%) completed surgery. Median age was 66 years; stages were T1/T2/T3/T4 (8.0/25/59/6.0%) and N0/N+ (38/54%). RT use declined (P1:P6, 41%->18% p<0.001) while CT use increased (P2:P6, 63%->79%, p<0.001). NACT (P2:P6, 4.1%->23% p<0.001) and MACT (P2:P6, 1.6%->20%, p<0.001) use increased while ACT decreased (P2:P6, 58%->36%, p<0.001). CT is likely to be allocated to young patients (<65yo) with Stage II-III tumors located at the pancreatic head (OR>1.00, p<0.001). Median OS increased over time (P1:P6, 18mo->32mo, p<0.001). Multivariable analysis shows that Adjuvant RT (HR 0.84 [0.81-0.87], p<0.001) and all CT (NCT: HR 0.71 [0.66-0.77], p<0.001; ACT: HR 0.63 [0.60-0.66], p<0.001; MACT: HR 0.65 [0.60-0.71], p<0.001) improved OS. Conclusions: This study shows decreased RT and increased CT adoption from 2004-2021. Median OS improved over the years, potentially due to peri-operative advances during this study period. Trends in treatment use over 3-year periods. RTN (%) CTN (%) Neo CTN (%) MACTN(%) P1: 2004-2006N=2661 1087 (41) 0 (0) a 0 (0) a 0 (0) a P2: 2007-2009N=3185 1185 (37) 2021 (63) 129 (4.1) 50 (1.6) P3: 2010-2012N=3536 1226 (35) 2460 (70) 267 (7.6) 138 (3.9) P4: 2013-2015N=3947 1210 (31) 2880 (73) 434 (11) 244 (6.2) P5: 2016-2018N=4224 971 (23) 3256 (77) 676 (16) 491 (12) P6: 2019-2021N=4351 787 (18) 3430 (79) 1003 (23) 857 (20) a No cohorts reported chemotherapy use during period 1. RT: Radiation Therapy; CT: Chemotherapy; NCT: Neoadjuvant Chemotherapy; MACT: Multiagent Chemotherapy.