Studying Outcomes after Steroid-Sparing Immunosuppressive Agent vs. Steroid-Only Treatment for Immune-Related Adverse Events in Non-Small-Cell Lung Cancer (NSCLC) and Melanoma: A Retrospective Case-Control Study

Simple Summary Corticosteroid use for the treatment of immune related adverse events (irAEs) after immune checkpoint inhibitor (ICI) use comes with concerns of side effects and the potential abrogation of antitumor immunity. Relatedly, the impact of steroid-sparing immunosuppressive agents (SSIAs) for treatment of irAEs on tumor outcomes is not well known, and current literature on this topic is limited by study design and issues around immortal time bias. This retrospective case-control study accounts for immortal time bias via strategic statistical methodology. Our results suggest that SSIAs used for irAE treatment may not negatively impact cancer outcomes in malignant melanoma and non-small cell lung cancer. For patients with melanoma, our results demonstrated better progression free survival for patients treated with infliximab compared to patients treated with corticosteroid monotherapy for irAEs. This study supports the safety for utilizing SSIAs for irAE treatment in patients receiving immune checkpoint inhibitors. Our study also encourages accounting for immortal time bias in the design of other observational studies in this space to accurately convey results and draw clinically meaningful conclusions.Abstract Background: The effects of steroid-sparing immunosuppressive agents (SSIAs), used for the treatment of immune-related adverse events (irAEs), on immune checkpoint inhibitor (ICI) antitumor activity is not well known. We compared tumor outcomes of patients who received corticosteroid monotherapy (CS) versus a corticosteroid plus SSIA (CS-SSIA) for irAE treatment, using statistical methods to address immortal time bias. Methods: We conducted a retrospective case-control study on patients >= 18 years with melanoma or non-small-cell lung cancer (NSCLC) treated with >= 1 ICI at a quaternary care center between 1 January 2016 and 11 January 2021. Patients were divided into two cohorts: CS or CS-SSIA. We used propensity score nearest-neighbor matching to match on tumor type, stage, and prior lines of therapy. Primary outcomes were progression-free survival (PFS) and overall survival (OS). Secondary outcomes included the time from the start of the irAE treatment to the irAE resolution. Hazard ratios (HRs) for PFS and OS were calculated using the Cox proportional hazard regression method with both (1) the time to the steroid and SSIA as time-varying covariates and (2) a binary exposure classification not accounting for the time to the treatment. Results: A total of 167 patients were included after matching (132 in the CS cohort and 35 in the CS-SSIA cohort). Sixty-six percent of all the patients had melanoma. The most common irAEs requiring treatment were gastroenterocolitis and hepatitis. In an adjusted analysis not accounting for immortal time bias, there were no significant differences in PFS (HR 0.75, 95% CI [0.46-1.23]) or OS (HR 0.82, 95% CI [0.46-1.47]). In analyses using a time-varying treatment indicator, there was a trend toward improved PFS in patients treated with SSIAs (HR 0.54, CI 0.26-1.10). There was no difference in OS (HR 1.11, CI 0.55-2.23). Patients with melanoma who specifically received infliximab had improved PFS compared to patients with CS only, after adjusting for immortal time bias (HR 0.32, CI 0.24-0.43). Conclusions: The use of SSIAs with CS did not have worse outcomes than CS monotherapy. In melanoma, our findings showed improved PFS for the use of infliximab versus steroid monotherapy for irAEs. Large, prospective, randomized controlled trials are needed to confirm these findings and guide the optimal treatment of irAEs.