Secondary neoplasms in patients treated for cancer: Etiology and perspective

The exact risk of secondary neoplasms in patients treated for cancer is difficult to ascertain due to a nonspecific increased risk, a possible genetic or congenital predisposition, and tumor multicentricity. Second tumors now considered 'treatment-related' may in fact, be 'syndrome-related', as in the case with secondary osteosarcoma in patients with retinoblastoma. A wide variety of second tumors have been described with solid tumors having latency periods of 10 years and with leukemia 5 years. Recently secondary lymphomas have been reported in Hodgkin's disease patients which may be related to their altered immunity. The 10-year risk of developing second cancers in patients with Hodgkin's disease or pediatric malignancies is approximately 10%, but the risk for all newly diagnosed cancer patients is below 1%. Aggressive treatment has improved curability; however, prolonged administration of chemotherapy, especially alkylating agents, and the use of radiotherapy plus chemotherapy have been major risk factors in the current excess of second cancers. Carcinogenic treatment should be avoided; however, patient curability must not be compromised until less toxic treatments are proven to be equally effective.