Purpose: The objective of this prospective study was to assess overall survival and event-free survival in patients with intraocular unilateral retinoblastoma (Reese-Ellsworth group V) treated by primary enucleation with or without adjuvant therapy depending on histopathologic risk factors.
Patients and methods: Patients (n = 123) were divided into three groups on the basis of risk factors for extraocular relapse and metastasis assessed on centralized histologic examination of enucleated eyes. Group 1 (n = 70) had minimal or no choroidal involvement and/or prelaminar or no optic nerve involvement and received no adjuvant therapy. Group 2 (n = 52) had massive choroidal involvement and/or intra- or retrolaminar optic nerve involvement and/or anterior segment involvement and received four courses of adjuvant chemotherapy. Group 3 (n = 1) had invasion of the surgical margin of the optic nerve and/or microscopic extrascleral involvement and received six courses of adjuvant chemotherapy with intrathecal thiotepa, consolidation chemotherapy, and autologous stem-cell rescue. Genetic testing was also performed.
Results: Median follow-up for the 123 patients was 71 months. No disease progression, relapse, or distant metastasis occurred during follow-up. No second malignancies occurred. This requires confirmation with longer follow-up. Secondary bilateralization occurred in two patients with identified RB1 germline mutation. Adjuvant chemotherapy was well tolerated, with limited toxicity. Molecular testing found constitutional RB1 gene mutations in only nine of 100 evaluated patients.
Conclusion: The survival rate of 100% was excellent, including 57% of patients who received no adjuvant therapy, suggesting that chemotherapy could be de-escalated in some patients, especially those with massive choroidal involvement.