Second nonocular tumors in retinoblastoma survivors. Are they radiation-induced?

A review of 693 patients with bilateral retinoblastoma and 18 patients with unilateral/germinal retinoblastoma was carried out to find the incidence, time, course and pattern of second nonocular tumors in retinoblastoma survivors. Of 688 patients who survived therapeutic radiation for retinoblastoma, 89 developed second tumors: 62 in the field of radiation and 27 out of the field. Of 23 patients who received no radiation, five developed second tumors: one in the field and four out of the field. The most common tumor found was a sarcoma both in and out of the field of radiation. The incidence of second tumors increases with time, although the mean latent period is 10.4 years. At 10 years, the incidence of second tumors is 20%, at 20 years, it is 50% and at 30 years, 90%. The incidence of tumors in patients treated without radiation and where tumors developed outside the field was 10% at 10 years, 30% at 20 years and 68% at 32 years. There was no relationship between incidence of tumors and dose of therapeutic radiation when analyzed with life tables. A second course of radiation therapy did not increase the incidence of second nonocular tumors.