The role of platinum-free interval in advanced endometrial cancer treatment: A real-world study of 843 patients.

5609 Background: Time between completion of last platinum-based chemotherapy (PBC) and recurrence is predictive of outcomes in recurrent ovarian cancer; however, its applicability to endometrial cancer (EC) remains uncertain. This retrospective real-world study assessed (1) platinum-free interval (PFI) duration between first-line (1L) PBC and second-line (2L) therapy for EC, (2) differences in patient (pt) and clinical characteristics by PFI, and (3) the association between PFI and outcomes. Methods: Using the US Flatiron Health electronic health record–derived deidentified database, we analyzed pts with advanced or recurrent EC who received 1L PBC between 1/1/2013 and 8/31/2022. PFI was defined as the time between completion of PBC and the start date of any 2L therapy. Overall survival (OS), time to treatment discontinuation (TTD), and time to next treatment (TTNT) were analyzed using Kaplan-Meier methods. The association between PFI and clinical outcomes was examined using Cox regression models. Results: Of 843 pts, 575 (68%), 147 (17%), and 121 (14%) had a PFI of <6, ≥6 to <12, and ≥12 months (mo), respectively. Pts with advanced disease, carcinosarcoma histology, or a history of surgery or radiation were more likely to have shorter PFI; those with a body mass index of ≥40 kg/m 2 or PD-L1 negative/not detected were more likely to have longer PFI ( P <.05 for all). Pts with a PFI of <6, ≥6 to <12, or ≥12 mo had a median OS of 12.7, 17.9, or 30.5 mo and median TTNT of 9.8, 8.3, or 12.6 mo, respectively. Compared with pts with a ≥12-mo PFI, those with shorter PFI had a significantly higher risk of death, after adjusting for potential confounders (HR, 1.71 [95% CI, 1.27-2.29] for PFI of <6 mo; HR, 1.57 [95% CI, 1.12-2.20] for PFI of ≥6 to <12 mo). Median OS, TTD, and TTNT, and their association with PFI, are summarized in the Table. Conclusions: Our data suggest that platinum sensitivity is an applicable concept in advanced or recurrent EC and is associated with OS. These results may have implications for treatment selection and informing clinical trial designs in EC. OS, TTD, and TTNT from the start of 2L treatment by PFI duration. Total(N=843) PFI <6 mo(n=575) PFI ≥6 to <12 mo(n=147) PFI ≥12 mo(n=121) OS, median (95% CI), mo 14.9 (13.3-17.3) 12.7 (11.3-14.4) 17.9 (14.7-23.9) 30.5 (19.0-41.3) OS association with PFI, HR (95% CI) a 1.71 (1.27-2.29) b 1.57 (1.12-2.20) b REF TTD, median (95% CI), mo 3.9 (3.6-4.2) 3.6 (3.2-3.9) 4.4 (3.7-5.2) 5.1 (4.2-6.5) TTD association with PFI, HR (95% CI) a 1.26 (1.02-1.56) b 1.09 (0.84-1.41) REF TTNT, median (95% CI), mo 10.1 (9.0-11.1) 9.8 (8.5-11.3) 8.3 (6.9-10.3) 12.6 (10.3-15.9) TTNT association with PFI, HR (95% CI) a 1.20 (0.91-1.59) 1.44 (1.04-2.00) b REF a Cox regression models adjusted for prespecified potential confounders: PFI, race, age, ECOG performance status, histology, disease stage and grade at diagnosis, body mass index, MMR/MSI status, and receipt of 2L immunotherapy. b P <.05 vs REF.