Secondary Neoplasms After Radiotherapy for a Childhood Solid Tumor

This study was conducted to determine the outcome of patients who develop a second neoplasm after radiotherapy (RT) for a childhood solid tumor. From 1956 to 1998, 429 children with a malignant solid tumor were treated at a single radiation oncology facility. The medical records and radiotherapy charts were reviewed to determine if the patient developed a secondary neoplasm after treatment for malignancy. Twenty-three (5.4%) patients developed a secondary neoplasm. There were 12 males and 11 females with a median age at RT of 6.6 years (range, 2 months to 20 years). There were 14 malignant neoplasms in 13 (3.0%) and 14 benign neoplasms in 11 patients (2.6%). The types of initial solid tumors treated with RT were Ewing sarcoma in 6, Wilms tumor in 6, medulloblastoma in 5, neuroblastoma in 3, and other in 3. Median RT dose was 45 Gy (range, 12.3 to 60 Gy) using 4 MV in 9, 1.25 MV in 8, 250 KV in 4, and 6 MV photons in 1 patient. One child was treated using 15-MeV electrons. Fourteen had chemotherapy. Median follow-up was 23.2 years (range, 5.3 to 44.4 years). For the 14 malignant neoplasms, the median time interval from initial tumor to second malignancy was 10.1 years. The 14 second malignant neoplasms (SMN) were osteosarcoma in 3, breast carcinoma in 2, melanoma in 2, malignant fibrous histiocytoma in 1, dermatofibrosarcoma in 1, leiomyosarcoma in 1, mucoepidermoid carcinoma in 1, colon cancer in 1, chronic myelogenous leukemia in 1, and basal cell carcinoma in 1. Ten of the 14 SMN (71%) were at the edge or inside the RT field. The 5- and 10-year overall survival rate after diagnosis of an SMN was 69.2%; it was 70% for children with a SMN at the edge or inside the RT field and 66.7% for those outside of the RT field. The 14 benign neoplasms appeared at a median time of 16.9 years and included cervical intraepithelial neoplasia in 3, osteochondroma in 3, thyroid adenoma in 1, duodenal adenoma in 1, lipoma in 1, cherry angioma in 1, uterine leiomyoma in 1, ovarian cystadenofibroma in 1, and giant cell tumor in 1. Only 5 (36%) of the 14 benign tumors occurred in the RT field, with osteochondroma being the most common. Of 189 deaths occurring in 429 patients, only 3 (1.6%) were secondary to radiation-induced malignancy. Not all SMN in children receiving RT occur in the irradiated field. More than two-thirds of children with a radiation-induced malignancy are alive 10 years after the diagnosis of a SMN.