63P Treatment-free survival (TFS) in patients (pts) with mNSCLC treated with 1L nivolumab (NIVO) + ipilimumab (IPI) + 2 cycles of chemotherapy (chemo) vs chemo alone (4 cycles) in CheckMate (CM) 9LA

TFS, a novel endpoint that can capture time periods of disease control and durability of clinical benefit following treatment (tx) discontinuation. TFS may be particularly appropriate in immunotherapy where some pts have shown continued benefit following a defined course of tx. Here we present TFS analysis with 4 y of follow-up in pts with mNSCLC treated with 1L NIVO + IPI + chemo or chemo alone in CM 9LA. As previously reported, CM 9LA significantly improved OS with NIVO + IPI + chemo vs chemo (HR 0.69 [96.71% CI 0.55-0.87]). Analysis included all randomized pts who received NIVO + IPI (up to 2 y) + chemo (2 cycles; n = 361) or chemo (4 cycles; n = 358) up to 48 mo. TFS was defined as the restricted mean (r-mean) between Kaplan-Meier (KM) curves for time to tx cessation and time to subsequent tx/death. TFS was also divided into periods with/without ongoing grade ≥ 3 tx-related adverse events and estimated over 24-, and 48-mo periods from randomization. At 4 y, an estimated 21% of pts treated with NIVO + IPI + chemo were alive, and an estimated 17% were alive without any subsequent systemic tx. Of pts treated with chemo, OS rate of 16% was observed at 4 y, and 8% for those that were alive without any subsequent tx. Over the 48-mo period since randomization, for pts treated with NIVO + IPI + chemo vs chemo, r-mean OS was 22.2 vs 17.6 mo (difference 4.6 mo; 95% CI 2.19-7.01), and r-mean TFS was 7.5 vs 5.0 mo (difference 2.6 mo; 95% CI 1.05-4.16), which was 16% vs 10% of 48-mo period spent in TFS. Mean TFS with toxicity constituted a small proportion of the 48-mo period for both tx arms, resulting in r-mean TFS without toxicity of 6.8 vs 4.5 mo (difference 2.3 mo; 95% CI 0.76-3.79). Similar results were shown by tumor PD-L1 expression levels and will be presented. The proportion of mean time spent in TFS increased from 11% of 24-mo to 16% of 48-mo period in the NIVO + IPI + chemo arm, while decreased from 14% to 10% in the chemo arm. In this CM 9LA analysis, 1L NIVO + IPI + chemo demonstrated an improvement in TFS with and without toxicity, regardless of tumor PD-L1 expression level, over 48 mo compared with chemo. These data reflect durable clinical benefit of NIVO + IPI + chemo following tx cessation.