Incidence of second neoplasms in patients with bilateral retinoblastoma.

The cumulative incidence of second neoplasms in 215 patients with bilateral retinoblastoma was calculated using the life-table method. Second tumors developed in 4.4% of the patients during the first 10 years of follow-up, in 18.3% after 20 years, and in 26.1% after 30 years. The 30-year cumulative incidence was 35.1% for the 137 patients who received radiation therapy compared with an incidence rate of 5.8% for the 78 patients who did not receive radiation. In the 137 patients who received radiation, second tumors developed both inside and outside the field of therapy. There was a 30-year incidence rate of second tumors of 29.3% within the field of irradiation and 8.1% outside the field. The rate outside the field of irradiation (8.1%) was similar to that observed in nonirradiated patients (5.8%). Our findings indicate that carriers of the retinoblastoma gene have an increased incidence of second tumors, and that the incidence rate is further increased in patients who receive radiation therapy.