medwireNews: Final analysis of progression-free survival (PFS) in the GEMSTONE-301 trial shows a significant improvement with use of sugemalimab versus placebo after chemoradiotherapy (CRT) for stage III unresectable non-small-cell lung cancer (NSCLC), report Chinese researchers at the IASLC World Conference on Lung Cancer 2022 in Vienna, Austria.
Presenting author Yi-Long Wu (Guangdong Provincial People’s Hospital, Guangzhou) said the current PFS results were “in line” with the earlier preplanned interim analysis for the phase 3 study comparing the PD-L1 inhibitor with placebo in patients who had not progressed after receipt of concurrent (c) or sequential (s)CRT.
At the cutoff date of March 2022, median PFS was 10.5 months for the 255 participants randomly assigned to receive sugemalimab 1200 mg at 3-week intervals for up to 2 years versus a median 6.2 months for the 126 patients given placebo (stratified hazard ratio [HR]=0.65).
At 36 months, 26.1% of sugemalimab-treated patients and none of the controls were alive and free from progressive disease, the presenter reported.
Wu et al also examined the impact of type of CRT on PFS. Around two-thirds of patients received cCRT and among these participants, receipt of sugemalimab was associated with a trend toward better PFS versus placebo (median 15.7 vs 8.3 months; stratified HR=0.71), albeit this difference did not reach significance.
In addition, sugemalimab achieved a significant improvement in PFS compared with placebo among the remaining patients who were given sCRT (median 8.1 vs 4.1 months; stratified HR=0.57).
However, session discussant Linda Martin (University of Virginia, Charlottesville, USA) observed that the “tiny numbers” of patients remaining in the CRT subgroups by the end of PFS follow-up “made it difficult to make too many assumptions” about this outcome. She remarked that durvalumab had “achieved much more robust numbers and reasonably similar outcomes” in the PACIFIC trial.
Turning to OS, Wu said that while the data had yet to mature, interim analysis showed an unreached median OS with sugemalimab versus 25.9 months with placebo (stratified HR=0.69). There was a similar pattern with use of the PD-L1 inhibitor after cCRT (unreached vs 32.4 months; stratified HR=0.75) and sCRT (unreached vs 24.1 months; stratified HR=0.60).
The investigator also observed that a similar proportion of the sugemalimab and placebo arms achieved a response to treatment (24.5 vs 25.2%), but patients given sugemalimab had a significantly longer median duration of response, at 24.1 months versus 6.9 months with placebo.
Reporting no new safety signals for sugemalimab and a “similar” toxicity profile to other available immunotherapy agents, the presenter concluded that “sugemalimab could be safety and effectively used after cCRT or sCRT and become a standard of care in this setting.”
But Martin noted that the GEMSTONE-301 trial compared sugemalimab with placebo, despite durvalumab having already received US FDA approval for this indication, and sugemalimab is “not clearly better” than the standard of care durvalumab.
She also questioned whether the GEMSTONE-301 trial might just be demonstrating the “superiority” of cCRT over sCRT rather than that of sugemalimab over placebo.
Noting that a third of trial participants received sCRT despite having an ECOG performance status of 0–1 and therefore not meeting frailty criteria that excludes use of cCRT, Martin suggested that PFS might have been improved in the study with greater use of cCRT regardless of adjuvant immunotherapy.
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