(025) Overall survival in immune checkpoint inhibitor-treated patients with rheumatoid arthritis and non-small cell lung cancer: a Medicare claims study

Background: Patients with autoimmune diseases, such as rheumatoid arthritis (RA), were excluded from clinical trials for immune checkpoint inhibitors (ICI). RA patients have a higher risk of certain cancers, including a 60% higher risk of lung cancer. This exclusion has yielded uncertainty in the comparability of the overall survival benefits of ICI treatment in non-small cell lung cancer (NSCLC) patients with RA.

Objectives: The aim of this study was to compare overall survival in ICI-treated patients with metastatic NSCLC (mNSCLC) with pre-existing RA versus compared to patients without RA. Clinicians and researchers involved in ICI treated cancer patients with autoimmune disease and RA.

Methods: We used a curated Medicare claims dataset that consist of a 100% sample of patients with RA and for the non RA comparator group we used the 5% random Medicare sample. Healthcare Common Procedure Coding System (HCPCS) codes were used to identify ICI treatment. Patients had to initiate ICI treatment between 2015-2019 when it was approved only for mNSCLC, and not for earlier stages or other types of lung cancer. mNSCLC was defined by having two claims at least two months apart associated with an ICD-9 162.9 or ICD-10 C34.X diagnosis code for malignant neoplasm of lung and bronchus. RA was defined as having two claims associated with an ICD-9-CM or ICD-10-CM diagnosis code for RA. Patients were followed through 12/31/2019 which was the end of the available data.

Descriptive statistics were calculated. Overall survival was determined by using Kaplan Meier curves and adjusted Cox proportional hazard models were performed anchored at the time of first ICI initiation. Models were adjusted for demographics, comorbid conditions, and cancer treatment factors.

Results: 2,732 people with NSCLC were included (N=790 RA and N=1942 non-RA). RA patients had more comorbidities, including interstitial lung disease and chronic obstructive pulmonary disease compared to non-RA patients.

Also, RA patients had a higher frequency of receiving ICI alone (without chemotherapy) (84.7%, N=669 versus non-RA patients, N=1605, 82.6%) and as a first-line therapy (41.4% RA compared to 38.9% of non-RA patients).

There was no difference between the RA and non-RA NSCLC Kaplan Meier curves (log-rank p-value=0.08). However, in adjusted Cox proportional hazard models, RA patients had 13% worse overall survival (HR 1.13 [95%CI 1.03, 1.25]) compared to non-RA patients.

Conclusions: RA cancer patients with NSCLC had a higher hazard of death compared to non-RA patients in adjusted models. More research is needed to determine if increased hazard of death is due to RA disease exacerbation (flares) or immune related adverse events resulting in early ICI discontinuation.