## Chemoreduction in Retinoblastoma **Key Point:** Carboplatin is the backbone agent in systemic chemotherapy for retinoblastoma, used as part of combination regimens (typically carboplatin + vincristine + etoposide) for chemoreduction. ### Role of Chemotherapy in Retinoblastoma Chemoreduction (neoadjuvant chemotherapy) is employed to: - Shrink intraocular tumors before focal therapy (laser, cryotherapy, brachytherapy) - Preserve globe and vision in unilateral or bilateral disease - Reduce tumor burden before external beam radiotherapy (EBRT) or enucleation ### Standard Chemoreduction Regimen The most commonly used protocol is **triple-agent chemotherapy:** | Agent | Role | Notes | | --- | --- | --- | | **Carboplatin** | Alkylating agent (backbone) | Penetrates blood–retinal barrier; primary cytotoxic agent | | **Vincristine** | Vinca alkaloid | Synergistic with carboplatin; enhances response | | **Etoposide** | Topoisomerase II inhibitor | Completes triple therapy; improves globe salvage | **High-Yield:** Carboplatin is the **single most important agent** in retinoblastoma chemotherapy because of its superior intraocular penetration and efficacy. It is dosed at 18.6 mg/kg IV every 28 days for 6 cycles. ### Clinical Pearl Chemoreduction followed by focal consolidation (laser/cryotherapy/brachytherapy) achieves globe salvage in 70–80% of eyes with intraocular disease, avoiding the morbidity of enucleation or external beam radiotherapy in children. ### Why Carboplatin is Preferred 1. **Pharmacokinetics:** Achieves therapeutic concentrations in the vitreous and retina 2. **Efficacy:** Highest response rate when combined with vincristine and etoposide 3. **Tolerability:** Better tolerated than doxorubicin in pediatric populations 4. **Evidence:** Standard of care per COG (Children's Oncology Group) and international guidelines
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