Stereotactic body radiotherapy-induced abscopal effect twice after pembrolizumab failure in hereditary leiomyomatosis and renal cell carcinoma: a case report with genetic and immunologic analysis

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) is a rare but aggressive disease. Immune checkpoint inhibitors (ICIs) have been an indispensable component for the management of advanced renal cell carcinoma, and stereotactic body radiotherapy (SBRT) has offered additional immunological effect boost for improving the treatment outcomes of the patients. However, the synergistic effect of ICIs with SBRT in HLRCC remains largely unexplored. We present the case of a 34-year-old woman with advanced HLRCC who underwent radical nephrectomy but soon relapsed at the retroperitoneal lymph nodes (RPLN). She was prescribed sunitinib but still progressed on twenty cycles with bulky RPLN and ascites. She was then treated with axitinib and pembrolizumab for twenty months, and received SBRT for the progression of RPLN upon which the first abscopal effect was observed via significant shrinkage of in-field and out-field tumor lesions. Five months later, she underwent a second course of SBRT for pelvic mass progression and the second abscopal effect was observed. Genetic and immunologic characteristics revealed a large number of tumor-infiltrating immune cells and high levels of PD-L1 expression. This case report demonstrates the synergistic effect of ICIs and SBRT in HLRCC and the potential mechanism for the repeated SBRT-induced abscopal effect, supporting the application of SBRT to oligometastatic lesion during ICIs treatment to delay disease progression. Further studies are needed to verify the strategy of combining ICIs and SBRT in advanced HLRCC.