Efficacy and safety of maintenance immune checkpoint inhibitors with or without pemetrexed in advanced non-squamous non-small cell lung cancer: a retrospective study.

Background: Advanced non-squamous non-small cell lung cancer (NS-NSCLC) patients without driver gene mutations are usually treated with immune checkpoint inhibitors (ICIs) plus pemetrexed as maintenance therapy after first-line ICIs plus 4-6 cycles of pemetrexed/platinum. Some patients in the real world receive ICIs monotherapy as maintenance therapy. No clinical study has compared the efficacy and safety of ICIs with or without pemetrexed as maintenance therapy.

Methods: We performed a retrospective study analyzing clinical data of patients with NS-NSCLC who were diagnosed in Zhejiang Cancer Hospital from September 2018 to May 2021 and received maintenance therapy after 4-6 cycles of ICIs plus pemetrexed/platinum. Patients were divided into ICIs plus pemetrexed group and ICIs monotherapy group. Progression Free Survival 1 (PFS1) and PFS2, defined as the interval from the date of initial treatment and maintenance therapy to the date of systemic progression/death or the last follow-up, respectively.

Results: A total of 120 patients received ICIs with or without pemetrexed as maintenance therapy. Eighty-two patients received ICIs plus pemetrexed as maintenance therapy, and 38 patients received ICIs monotherapy. There were no statistically significant difference in median PFS1 between the ICIs monotherapy group and ICIs plus pemetrexed group (12.00 months vs. 12.07 months, P = 0.979). Among patients with PD-L1 TPS < 1%, the median PFS1 was worse with ICIs monotherapy (9.50 months vs. 14.20 months, P = 0.039). Among patients with PD-L1 TPS ≥50% or 1-49%, the median PFS1 in both groups was not statistically significant (P = 0.866, P = 0.589, respectively). Results for median PFS2 were similar to median PFS1, with statistically significantly different only in patients with PD-L1 TPS < 1% (P = 0.008). The 2-year survival rates of the two groups were similar (66.7% vs. 69.5%, P = 0.812). The incidence of fatigue was significantly higher in the ICIs plus pemetrexed group (P = 0.023).

Conclusions: ICIs with or without pemetrexed can be used as maintenance therapy after first-line ICIs plus 4-6 cycles of pemetrexed/platinum in patients with advanced NS-NSCLC based on PD-L1 expression.