# Use of Radiation Therapy for Ataxia-Telangiectasia Mutated (ATM)-Mutation Metastatic Renal Cell Carcinoma: A Case Report

## TL;DR

A patient with a rare kidney cancer and an ATM mutation showed long-term disease stability after radiation therapy, possibly due to tumor sensitivity from the mutation.

## Contribution

This case report suggests radiation therapy may be effective for ATM-mutated metastatic papillary renal cell carcinoma.

## Key findings

- The patient's disease remained stable for 10 months after radiation therapy despite treatment discontinuation.
- ATM mutation may enhance tumor sensitivity to radiation, leading to prolonged progression-free survival.
- Radiation therapy was well-tolerated and provided clinical benefit in this rare cancer subtype.

## Abstract

Papillary renal cell carcinoma (pRCC) is a rare kidney cancer with limited treatment options and poor outcomes when metastatic. We present a case of a 42-year-old male with metastatic pRCC harboring a somatic ataxia-telangiectasia mutated (ATM) mutation who was treated at our institution. After progression of disease (POD) on ipilimumab/nivolumab, followed by POD on cabozantinib, the patient was treated with radiation therapy to metastatic cervical lymphadenopathy to 60 Gy in 15 fractions as well as retroperitoneal lymphadenopathy to 36 Gy in 9 fractions, which was curtailed due to intolerance. This was followed by sequential systemic therapy with a poly (ADP-ribose) polymerase (PARP) inhibitor and pembrolizumab, which was also discontinued due to adverse effects. Despite not receiving any treatment for 10 months, his disease remains stable. We believe that the prolonged progression-free survival of this patient with ATM-mutation metastatic pRCC is likely due to the enhanced sensitivity of the tumor to radiation therapy due to ATM loss.