A recent phase III clinical trial, EXTENTORCH, has demonstrated that the addition of toripalimab, a PD-1 inhibitor, to first-line chemotherapy significantly improves both progression-free survival (PFS) and overall survival (OS) in patients with extensive-stage small cell lung cancer (ES-SCLC). The study, a multi-center, double-blind trial, offers a promising new treatment option for this aggressive disease.
The EXTENTORCH trial, involving 442 patients, randomized participants to receive either toripalimab (240 mg) or placebo in combination with etoposide plus cisplatin or carboplatin (EP) chemotherapy. Treatment was administered every 3 weeks for up to 4-6 cycles, followed by maintenance therapy with toripalimab or placebo until disease progression or unacceptable toxicity. The primary endpoint was investigator-assessed PFS.
Significant Improvement in Survival Rates
The results indicated a statistically significant improvement in PFS for the toripalimab group, with a median PFS of 5.8 months (95% CI: 5.6-6.8 months) compared to 5.6 months (95% CI: 5.5-5.7 months) in the placebo group (HR=0.67, 95% CI: 0.54-0.82, P < .001). The 6- and 12-month PFS rates were 47.1% vs 36.3% and 18.1% vs 4.9%, respectively.
Furthermore, the toripalimab combination demonstrated a statistically significant improvement in OS, with a median OS of 14.6 months (95% CI: 12.9-16.6 months) compared to 13.3 months (95% CI: 11.8-14.4 months) in the placebo group (HR = 0.80, 95% CI = 0.65-0.98, P = .03). The 12- and 24-month OS rates were 63.1% vs 54.9% and 25.9% vs 19.5%, respectively.
Biomarker Analysis and Genomic Profiling
Whole-exome sequencing data from 300 patients revealed potential biomarkers associated with favorable outcomes in the toripalimab group. Low intratumor heterogeneity, specific HLA haplotypes (HLA-A11+ HLA-B62), wild-type KMT2D and COL4A4, and sequence variations in CTNNA2 or SCN4A correlated with improved PFS and OS.
Further analysis identified that mutations in the FA-PI3K-Akt pathway and IL-7 signaling pathway were associated with improved OS in the toripalimab group.
Safety Profile
The safety profile of the toripalimab combination was generally acceptable. Grade ≥ 3 adverse events occurred in 89.6% of the toripalimab group and 89.4% of the control group. The most common adverse events in both groups were decreased neutrophils, decreased white blood cell counts, and anemia. Serious adverse events occurred in 50% vs 37.5% of patients. Adverse events led to treatment discontinuation in 12.6% vs 7.9%. Fatal adverse events occurred in 12 patients (5.4%) in the toripalimab group vs 7 patients (3.3%) in the control group.
Implications for Clinical Practice
The EXTENTORCH trial provides compelling evidence for the efficacy and safety of adding toripalimab to first-line chemotherapy in patients with ES-SCLC. These findings support the use of this combination regimen as a new treatment option, potentially improving survival outcomes for patients with this challenging disease. Further research is warranted to validate the identified biomarkers and optimize treatment strategies based on individual patient characteristics.
