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5607 Background: Dostarlimab (DOST)+carboplatin-paclitaxel (CP) significantly improved PFS and OS vs CP alone in patients (pts) with primary advanced or recurrent endometrial cancer (pA/rEC) in the phase 3RUBY trial (NCT03981796). Safety has been reported for immunotherapy+chemotherapy combinations in EC, though timing of adverse events (AEs) and the longer-term AE profile is not yet clear. This analysis examines the time course of AEs related to any study treatment (TRAEs) during the RUBY trial. Methods: Pts with pA/rEC were randomized 1:1 to DOST+CP or placebo (PBO)+CP Q3W (6 cycles), followed by DOST or PBO monotherapy Q6W for up to 3 years. AEs were assessed according to CTCAE v4.03 and summarized by quarter. Results: The safety population included 487 pts who received ≥1 dose of treatment (241 DOST+CP; 246 PBO+CP). TRAEs were experienced by 97.9% of pts in the DOST+CP arm and 98.8% of pts in the PBO+CP arm. In both arms, the majority of the most common TRAEs (≥30%) and grade ≥3 TRAEs (≥10%) occurred within the first 3 to 6 months of treatment (Table). The timing of immune-related AEs (irAEs) was generally consistent with this finding. Conclusions: The majority of TRAEs seen in the RUBY trial occurred within the first 3 to 6 months, with limited differences between arms. This timing is consistent with the pts’ receipt of chemotherapy. Few pts experienced an onset of new TRAEs in the DOST+CP arm after 12 months. These safety data further support a favorable long-term benefit-risk profile of dostarlimab+CP in pts with primary advanced or recurrent EC. Clinical trial information: NCT03981796 . Table: see text
Lokich et al. (Sat,) studied this question.