Median overall survival was similar at 21.0 months and 22.1 months in 169 patients who received cancer immunotherapy plus chemotherapy and 351 who received cancer immunotherapy monotherapy, respectively (adjusted hazard ratio, 1.03). Median real-world progression-free survival (PFS) was also similar in the two groups (10.8 vs. 11.5 months; aHR, 1.04), Solange Peters, MD, reported at the 2021 European Society for Medical Oncology Congress on Sept. 17 (abstract VP2_2021).
However, in a small subgroup of 50 never-smokers, CIT plus chemotherapy showed significant and meaningful improvement in both overall survival and real-world progression-free survival, compared with CIT monotherapy, said Dr. Peters, ESMO president and professor and chair of medical oncology at the Centre Hospitalier Universitaire Vaudois, Lausanne, Switzerland.
The hazard ratios for overall survival and progression-free survival, after adjusting for baseline characteristics, were 0.50 and 0.40 in this subgroup, Dr. Peters said.
She and her colleagues reviewed data from the nationwide Flatiron Health Electronic Health Record–derived deidentified database for patients with metastatic nonsquamous NSCLC with a PD-L1 tumor proportion score at least 50% expression who initiated first-line CIT monotherapy or CIT plus chemotherapy between Oct. 24, 2016, and Feb. 28, 2019.
Median follow-up was 23.5 and 19.9 months in the monotherapy and combination therapy groups, respectively.
The findings are notable because “this is a very important scientific question, which by the way, is a daily question we have,” Dr. Peters said during a plenary debate session at the conference.
“One in four patients [with metastatic nonsquamous NSCLC has] this high PDL expression,” she explained, noting that both treatment approaches are commonly used in the first-line setting in this patient population.
The findings highlight the value of “well-conducted real-world evidence trials” in the absence of randomized trial results, she said.
Invited discussant Marina Chiara Garassino, MBBS, professor of medicine at the University of Chicago, also acknowledged the importance of the findings, noting the “multiple possibilities” for treatment selection in the metastatic nonsquamous NSCLC patient population.
Although patients with PD-L1 expression below 50% derive clear benefit from combination versus single-agent therapy, treatment selection for those with high PD-L1 expression is “very tricky and debatable,” she said.
For those with high PD-L1 expression, the choice is less clear and wrought with uncertainties – particularly for certain subgroups like never-smokers and those with PD-L1 expression over 90%, she said.
The findings reinforce those seen in prior meta-analyses and other clinical trials, particularly with respect to the role of smoking history when making treatment decisions.
“After these results and previous subgroup analyses, in my opinion, in [patients with] PD-L1 expression over 50%, we should consider the combination of chemotherapy and immunotherapy,” she said.
Conversely, findings from this study showing no difference in outcomes between the treatment approaches in patients with brain or liver metastases are based on small numbers and lack power for drawing any conclusions, she said. It also remains unclear whether there is a differential effect for women and those with PD-L1 expression over 90%, high tumor mutation burden, performance score greater than 2, and age over 75 years.
Both Dr. Garassino and Dr. Peters said they are looking to the INSIGNA trial, which is currently recruiting patients in the United States to evaluate the timing of pembrolizumab alone or with chemotherapy as first-line treatment and maintenance in NSCLC, to provide more clarification regarding the best treatment approaches.
This study was funded by F. Hoffmann–La Roche. Dr. Peters and Dr. Garassino each disclosed personal and/or institutional financial relationships with numerous pharmaceutical companies.