Outcomes of Immunotherapy (ICI) Alone vs. Stereotactic Radiosurgery (SRS) Alone vs. ICI and SRS Combined in Renal Cell Carcinoma Brain Metastasis

Purpose/Objective(s)

Renal cell carcinoma is the fourth most common cause of metastatic brain tumors. Both Immune Checkpoint Inhibitors (ICIs) and Stereotactic Radiosurgery (SRS) have been used as first line treatment for renal cell carcinoma brain metastasis (RCCBM). The efficacy of ICIs alone, SRS alone, or SRS and ICIs combined as treatment is being evaluated. We hypothesize that a combination of SRS and ICIs will lead to an improvement in Overall Survival (OS), when compared to either alone, for patients with RCCBM.

Materials/Methods

Patients with RCCBM treated at our tertiary care center (2010-2020) with either ICIs, SRS, or both were evaluated. Overall Survival (OS) was measured from initiation of immunotherapy or SRS of RCCBM to date of death or last follow up. The Cox proportional hazard model was used to determine differences in OS.

Results

210 patients with RCCBM were included. Of these, 26 were treated with ICIs alone, 80 were treated with SRS alone, and 104 were treated with a combination. For treatment with ICIs alone, the median age at diagnosis was 61 years (Interquartile range (IQR) 45-82), 63% of the patients were male, and 96% were white. For treatment with SRS alone the median age at diagnosis was 63 years (IQR 37-84), 70% of the patients were male, and 94% were white. For ICIs/SRS combination treatment, the median age at diagnosis was 63 years (IQR 38-79), 72% of the patients were male, and 97% were white. Overall Survival for patients treated with ICIs alone, SRS alone, and ICIs/SRS combined had a median of 25.4, 29.4, and 81.2 months and a 2 year rate of 56%, 53%, and 89%, respectively. With ICI treatment alone as a reference, SRS treatment alone had an OS hazard ratio, HR = 1.13 (95% CI = 0.69 – 1.84, P = 0.62), and ICI/SRS combination treatment had an OS hazard ratio, HR = 0.41 (95% CI = 0.24 – 0.69, P = < 0.001).

Conclusion

In patients with RCCBM, combination treatment with both ICIs and SRS was associated with an increase in Overall Survival when compared to treatment with ICIs alone or SRS alone. Further studies need to be done to control for other patient variables such as KPS/ECOG, number of lesions, and extra-cranial metastasis.