Second Malignant Neoplasms in Long-term Retinoblastoma Survivors: Retrospective Cohort Study of 491 Patients in Turkey.

Background: It has been reported that the risk of second malignant neoplasms (SMNs) in long-term follow-up patients with heritable retinoblastoma (Rb) is significantly increased compared with patients with non-heritable Rb and the general population. In this study, we investigated the types, frequencies, clinical and pathologic features, potential risk factors, and outcomes of SMNs occurring in a large group of retinoblastoma patients that were diagnosed, treated, and followed up for a long time in our Pediatric Oncology unit.

Methods: Our study comprehensively analyzed records of Rb patients followed up at Hacettepe University Pediatric Oncology Department over a 51-year period from January 1972 to January 2023. We determined the number, rate, and time of diagnosis of various SMN types and investigated potential risk factors that could lead to the development of SMNs.

Results: A total of 491 patients were included in this study. Median age at the time of retinoblastoma diagnosis was 1.25 (range, 0.02 to 12.08) years. Of these cases, 313 (63.7%) were unilateral, 174 (35.4%) were bilateral, and 4 (0.9%) were trilateral Rb. Enucleation was performed in 348 (70.9%) cases. A total of 334 cases received systemic chemotherapy with different protocols. Intra-arterial chemotherapy (IAC) was administered in 101 (20.6%) patients. Radiotherapy was administered in 76 (15.5%) patients. After enucleation, 56 (11.4%) patients were followed up without further treatment. SMNs occurred in 13 (2.6%) of 491 patients. Among these, 9 (69.2%) patients were considered as having heritable Rb. Enucleation was performed in 10 cases. Only 1 patient received radiotherapy and 12 patients received systemic chemotherapy. Most common subtype of SMNs was osteosarcoma (n=7; 53.8%), followed by acute myeloid leukemia (AML) (n=3; 23.1%), acute lymphoblastic leukemia (ALL) (n=1; 7.7%), Wilms tumor (n=1; 7.7%), and colon adenocarcinoma (n=1; 7.7%). The median time from the diagnosis of Rb to the onset of SMN was 136 (range, 24 to 250) months. Among the patients that underwent IAC, no patient developed SMN. Of the 491 patients, 41 (8.3%) died and 450 are still alive. Of the 13 patients with SMN, 8 (61.5%) died and 5 are still alive. Five-year OS of our study group was 91% and it was significantly lower in patients with SMNs compared with those without SMNs ( P =0.001).

Conclusion: In this study, overall survival (OS) was lower in patients with bilateral retinoblastoma compared with unilateral cases, and similarly reduced in patients who received radiotherapy compared with those who did not. In addition, the development of second malignant neoplasms (SMNs) was significantly higher in hereditary retinoblastoma patients than in non-hereditary cases. These findings highlight the importance of careful long-term monitoring and tailored follow-up strategies in patients at increased risk.