RADT-02. IMPACT OF SINGLE AND DUAL IMMUNE CHECKPOINT BLOCKADE ON RISK OF RADIATION NECROSIS AND LOCAL CONTROL AMONG PATIENTS WITH BRAIN METASTASES TREATED WITH STEREOTACTIC RADIOSURGERY

Abstract

Abstract PURPOSE Single and dual immune checkpoint inhibition (ICPI) are common treatment options for patients, particularly with melanoma and non-small cell lung cancer (NSCLC). While data suggest a cancer control benefit of combining stereotactic radiosurgery (SRS) and ICPI, we hypothesized that concurrent dual ICPI and SRS increases risk for radiation necrosis (RN). METHODS We retrospectively reviewed patients with metastatic melanoma or NSCLC treated with SRS for intact brain metastases from 2014-2020. Patients were stratified by receipt of dual ICPI, single ICPI, and SRS alone. Concurrent ICPI was defined as treatment within 30 days of SRS. RN and local control (LC) were biopsy confirmed or determined radiographically and longitudinally, in combination with clinical assessment and steroid use. Kaplan-Meier estimates were used to compare rates of RN and LC between cohorts. RESULTS 673 brain lesions from 93 patients met inclusion criteria [median (Q1, Q3): 5.0 (2.0-10.0) lesions per patient]. Median follow-up was 8.1 months (95% CI: 7.3-8.7). Histologies included melanoma (53.5%), adenocarcinoma NSCLC (27.3%), squamous cell NSCLC (6.1%), and NSCLC NOS (6.1%). 88 lesions from 25 patients (27%) developed RN and 11 (13%) were biopsy-proven. ICPI use was enriched among lesions that developed RN (85.2%) versus those that did not (19.8%). RN was associated with concurrent ICPI (p< 0.001). Freedom from RN at 6 months was 80% for dual ICPI, 82% for single ICPI, and 97% for SRS alone; 12-month rates were 78% in each ICPI cohort and 95% with SRS alone (p=0.0002). LC differed among dual (97.5%), single (88.7%), and no ICPI (79.7%, p < 0.001). There was a trend toward improved LC with RN (96.6% vs 91.8%; p=0.087). CONCLUSIONS In a large cohort of brain metastases, we observed increased risk of RN and improved LC with SRS plus concurrent dual or single ICPI. Awareness of these associations is critical for patient management.