Dynamic tumor-tracking stereotactic body radiation therapy for a solitary tumor in a transplanted organ: two case reports.

Solid-organ transplant recipients require long-term immunosuppressants to prevent graft rejection. However, immunosuppressant use increases the risk of malignancy. Radiotherapy can be a treatment option for patients who are medically inoperable or refuse surgery; however, whether the irradiation of transplanted organs is safe remains unclear. We present two patients with malignancies that developed in transplanted organs and were treated with dynamic tumor-tracking (DTT) stereotactic body radiation therapy (SBRT). The first patient underwent transplantation owing to liver cirrhosis caused by hepatitis C virus and subsequently developed hepatocellular carcinoma in the donated liver. There was no evidence of recurrence 12 months post-treatment, and liver function enzyme levels did not deviate from their pre-SBRT baselines. The second patient had a solitary tongue cancer metastasis in a transplanted lung; she also had a history of interstitial pneumonia caused by scleroderma. Six weeks after DTT-SBRT, she developed grade 3 radiation pneumonitis but recovered with oral steroids; she experienced no tumor recurrence after 14 months, although her respiratory function was worse than it was pre-SBRT owing to post-transplant rejection. DTT-SBRT is thus feasible for treating tumors that arise in transplanted lungs and livers. © The Japan Society of Clinical Oncology 2020.