Two cases of gastrointestinal perforation after radiotherapy in patients receiving tyrosine kinase inhibitor for advanced renal cell carcinoma

We report two cases of gastrointestinal perforation (GIP) after radiotherapy in patients receiving tyrosine kinase inhibitor (TKI) for advanced renal cell carcinoma (RCC). Case 1 was a 61-year-old woman with lung metastases after a radical nephrectomy for a right RCC (cT3aN0M0) treated with interferon-alpha (OIF, 5 MIU, three times per week). She developed lytic metastases of the left femur and the left acetabulum. She was treated with palliative radiotherapy to the metastatic portion (3 Gy × 10 fractions), and 400 mg sorafenib twice per day plus continuing interferon alpha. She experienced sudden left lower abdominal pain after four weeks of treatment, and was diagnosed with a perforation of the sigmoid colon with fecal peritonitis. Case 2 was a 48-year-old man with lung, lymph node, and bone metastases after a radical nephrectomy for a right RCC (cT2N0M0), and was treated with 400 mg sorafenib twice per day. He developed lytic bone metastases of the lumbar vertebrae, which was treated with palliative radiotherapy to L2-4 (3 Gy × 10 fractions). He experienced sudden abdominal pain after two months of radiation treatment, and was diagnosed with a perforation of the sigmoid colon with fecal peritonitis. These cases underwent radiotherapy, and therefore this may be related to the radiosensitivity of TKI.