Li-Fraumeni syndrome (LFS) is a genetic disease that is hypersensitive to radiotherapy. Proton therapy (PT) was strongly recommended for pediatric and radiation-sensitive tumors. However, there is little information on PT for LFS. The patient was a 7-year-old girl with LFS who was diagnosed with radiation-induced right shoulder blade osteosarcoma and left chest wall malignant fibrous histiocytoma. Both tumors were in the area that had previously been irradiated (36-45 Gy by photon radiotherapy). Sixty-six GyE in 30 fractions was planned for both tumors. We set the clinical target to the minimum gross tumor volume. To comprehensively assess any adverse events, PT was conducted under hospital administration. Cisplatin was used as simultaneous combination chemotherapy. Although administration of granulocyte-colony stimulating factor was necessary for myelosuppression by chemotherapy, PT was completed without interruption. Acute radiation toxicity was observed as Grade 1 dermatitis. The dermatitis became exacerbated 2 weeks after PT but subsequently improved with conservation treatment alone. Twenty-three months after PT, magnetic resonance imaging showed an increase in the tumor on the right shoulder. A histological examination was not conducted as the family declined, but secondary cancer was suggested rather than recurrent osteosarcoma, as the tumor developed mainly from the soft tissue. Additional surgical treatment and radiotherapy were not indicated, and the patient died of tumor progression and sepsis caused by myelosuppression 27 months after undergoing PT. Up to 23 months after PT, there were no signs of Grade 2 or more late toxicities. This represents the first reported case of PT for a patient with LF to treat radiation-induced secondary cancer.
Keywords: Li-Fraumeni syndrome; pediatric; proton radiotherapy; proton therapy; secondary cancer.