(HealthDay News) — Risk classification based on histopathologic features is an effective approach to selecting appropriate adjuvant therapy for patients with intraocular unilateral retinoblastoma treated by primary enucleation, according to a study published online March 5 in the Journal of Clinical Oncology.

Isabelle Aerts, M.D., from the Institut Curie-Hopital in Paris, and colleagues analyzed three groups of patients classified based on risk factors for extraocular relapse and metastasis based on centralized histologic examination of enucleated eyes. Group 1 with 70 patients received no adjuvant therapy and had minimal or no choroidal involvement and/or prelaminar or no optic nerve involvement. Group 2 with 52 patients received four courses of adjuvant chemotherapy and had massive choroidal involvement and/or intra- or retrolaminar optic nerve involvement and/or anterior segment involvement. Group 3 with one patient received six courses of adjuvant chemotherapy with intrathecal thiotepa, consolidation chemotherapy, and autologous stem-cell rescue, and had invasion of the surgical margin of the optic nerve and/or microscopic extrascleral involvement. Genetic testing was also performed.

The researchers found that for the 123 patients median follow-up was 71 months, during which time there was no disease progression, relapse, or distant metastasis. No second malignancies were seen, but longer follow-up is necessary for confirmation. In two patients with identified RB1 germline mutation, secondary bilateralization occurred. Limited toxicity occurred with adjuvant chemotherapy. Constitutional RB1 gene mutations were identified with molecular testing in only nine of 100 evaluated patients.

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“The survival rate of 100 percent was excellent, including 57 percent of patients who received no adjuvant therapy, suggesting that chemotherapy could be de-escalated in some patients, especially those with massive choroidal involvement,” write the authors.

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