As the treatment of childhood cancer improves and more children are cured, there is a growing concern over the long-term toxicity of treatment. Possibly the mostconcerning toxicity is the development of a second tumor. Second tumors may be due to the treatment (chemotherapy and radiotherapy both can lead to tumor formation) orto genetics (children who have cancer maybe predisposed to developing a second cancer) or a combination of both. Two childhood tumors in particular have a high incidenceof second tumor formation: Ewing's sarcoma and retinoblastoma.
Ewing's sarcoma is a cancer that typically arises in the bones of teenagers and is treated with a combination of chemotherapy, surgery and radiotherapy. Because of reportsdetailing the formation of second cancers, the dose and amount of tissue receiving radiation has been reduced on most modern studies. In the September 1, 1998 issue of theInternational Journal of Radiation Oncology, Biology and Physics the German Ewing's Sarcoma Studies group reports the rate of second cancers in Ewing's patients whoreceived modern doses of radiotherapy.
Six hundred and seventy-four patients with Ewing's sarcoma were studied. All patients were treated between 1981 and 1991 with surgery and four chemotherapy agentsconsisting of vincristine, adriamycin, actinomycin D and either ifosfamide or cyclophosphamide. In addition, five hundred and twelve patients received radiation. The medianfollow-up time was 5.1 years.
Eight of the 674 patients developed a second cancer (1%). Four patients developed acute myelogenous leukemia, three developed sarcomas, and one case of myelodysplaticsyndrome was reported. The cases of acute myelogenous leukemia occurred one to six years after the diagnosis of Ewing's sarcoma. The three sarcomas occurred, on average,nine years after the diagnosis of Ewing's sarcoma. This data is consistent with other reports describing solid second cancers (such as sarcomas) to occur years followingtreatment while 'liquid' second tumors (leukemia and lymphoma) to occur sooner. All three sarcomas developed in an area that received radiation.
Statistical analysis revealed the risk of second tumor formation to be 1% at 5 years and 5% at fifteen years. The authors conclude that there is only a small risk of secondcancer formation after modern treatment of Ewing's sarcoma. And, that the use judicious of radiotherapy is justified in light of the low risk of radiation induced cancer.