The Dutch retinoblastoma registry was used to analyze risks of second primary malignancies in retinoblastoma patients diagnosed from 1945 to 2005. After extensive follow-up procedures, complete follow-up data of 668 (89%) retinoblastoma patients were obtained. Information of current health, past diseases, including any occurrence of cancer, medical treatments, and various risk factors for cancer were obtained by means of a mailed questionnaire and confirmed by pathology reports, hospital or physician’s records. For both hereditary and nonhereditary retinoblastoma patients, risks of second primary malignancies were compared with the Dutch general population. No statistically significantly elevated risks of second primary malignancies were found among nonhereditary retinoblastoma survivors (standardized incidence rate (SIR) = 1.86; 95% confidence interval (CI): 0.96–3.24, absolute excess risk (AER) = 0.57 per 1,000 person-years). Among hereditary retinoblastoma survivors an overall risk of 20.4 (95% CI: 15.6–26.1; AER = 8.61 per 1,000 person-years) was found, which increased almost with threefold when these patients were treated with radiotherapy. Because of the small number of hereditary retinoblastoma patients treated with chemotherapy exclusively, our ability to detect any association of chemotherapy with second solid malignancy was limited. Among hereditary retinoblastoma patients, the cumulative incidence of a second malignancy at 40 years after retinoblastoma diagnosis, accounting for death as a result of other causes as competing risk, was 28% (95% CI: 21.0–35%). Our results confirmed the strongly increased risks of soft tissue sarcoma, osteosarcoma, and melanoma in hereditary retinoblastoma survivors. However, after more than 40 years of follow-up an emerging excess of epithelial cancers (i.e., breast, lung and bladder) was observed, which had not been reported in other long-term follow-up studies.
