Effect of Radiotherapy (RT) on Outcomes in Patients (Pts) With Borderline Resectable and Locally Advanced Pancreatic Ductal Adenocarcinoma (BRPC, LAPC).

PURPOSE/OBJECTIVE(S) The role of RT remains controversial in treating BRPC and LAPC following Alliance A021501 and LAP07. These studies shifted our institutional practice to more selective use of RT, whereas in the past, we most often consolidated with RT after chemotherapy (chemo). We reviewed our experience using modern multi-agent chemo with or without RT. MATERIALS/METHODS We utilized a retrospective registry to analyze 454 pts (240 M, 214 F, median age 65 [28 - 89]) who were diagnosed with BRPC (n = 172) or LAPC (n = 282) between 2011 to 2019 and who underwent chemo alone (n = 167) or chemo then RT (n = 287). For those pts who received RT, the median dose and fractionation was 50 Gy (30 - 98 Gy) and 15 fractions (4 - 28). Median biological effective dose was 60 Gy (33 - 132 Gy). All pts received FOLFIRINOX (n = 274) or gemcitabine/nab-paclitaxel (GnP, n = 180). Associations between chemo regimen (FOLFIRINOX vs. GnP), resection (surgery vs. no surgery), CA19-9 response (normalized vs. not vs. not applicable [N/A]), and other demographic characteristics were tested using the likelihood-ratio. CA19-9 normalizers were defined by the minimum CA19-9 value between the start of chemo and 6 mos post-chemo start that was < 40 U/mL. Pts were classified as N/A if the pt either had an abnormal bilirubin level or a CA19-9 < 40 U/mL at baseline, or were missing CA19-9 data. Kaplan-Meier and Cox proportional hazards tests were used for survival analyses. RESULTS For all pts, median overall survival (OS) was 17.5 mos and median distant metastasis free survival (DMFS) was 11.5 mos. The chemo then RT group had a greater proportion of pts who received FOLFIRINOX than the chemo only group (64% vs 54%, P = 0.03). The chemo then RT group also had a greater percentage of pts who went to surgery than the chemo alone group (33% vs 16%, P < 0.0001). Pts with BRPC were more likely to receive surgery than pts with LAPC (48% vs. 14%, P < 0.0001). Univariate analyses showed that baseline stage (BRPC vs LAPC), surgery, CA19-9 response, and receipt of chemo then RT were associated with both OS and DMFS. Chemo regimen was associated with OS but not DMFS on univariate analysis. Multivariate analysis identified that surgery, CA19-9 response, and receipt of chemo then RT were independent prognostic factors for both OS and DMFS (Table). Multivariate analysis of only LAPC showed the same associations with OS and DMFS as with all pts. CONCLUSION RT following chemo was associated with better OS and DMFS compared with chemo alone in a modern retrospective BRPC and LAPC cohort. Additional studies are needed to clarify the role of RT.