A 3-year-old girl from Delhi is found to have bilateral retinoblastoma on screening — the right eye has a Group C tumour (medium-sized, no vitreous seeding) and the left eye has a Group B tumour (small, no vitreous involvement). Systemic staging (chest CT, abdominal ultrasound, bone marrow biopsy) shows no metastases. Intraocular pressures are normal bilaterally. The parents ask about treatment options. What is the most appropriate next step in management?

Explanation

## Bilateral Retinoblastoma: Globe-Salvaging Strategy **Key Point:** In bilateral retinoblastoma without metastatic disease, the goal is to preserve vision and life. Modern chemotherapy-first approaches (intra-arterial or systemic) have dramatically improved outcomes, allowing salvage of one or both eyes in many cases. Enucleation is reserved for eyes that fail chemotherapy or have advanced disease. ### Classification & Prognosis | Feature | Right Eye (Group C) | Left Eye (Group B) | | --- | --- | --- | | **Size** | Medium | Small | | **Vitreous seeding** | Absent | Absent | | **Salvage potential** | Moderate–good | Excellent | | **Primary treatment** | Chemotherapy | Chemotherapy | **High-Yield:** Groups A–C tumours without vitreous seeding have excellent prognosis (~95% eye salvage) with chemotherapy-first approaches. Bilateral disease does NOT mandate bilateral enucleation in the modern era. ### Chemotherapy Routes in Retinoblastoma ```mermaid flowchart TD A[Bilateral RB, Groups B-C, no metastases]:::outcome --> B{Vitreous seeding?}:::decision B -->|No/minimal| C[Intra-arterial chemotherapy IAC]:::action B -->|Extensive| D[Systemic chemotherapy + IAC]:::action C --> E{Response after 3-4 cycles?}:::decision E -->|Good| F[Continue IAC, monitor closely]:::action E -->|Poor| G[Add external beam RT or consider enucleation]:::action D --> H[Assess response]:::decision H -->|Salvageable| I[Continue chemotherapy]:::action H -->|Non-salvageable| J[Enucleation + systemic therapy]:::urgent ``` ### Why Intra-Arterial Chemotherapy (IAC)? **Mechanism:** Chemotherapy (melphalan, topotecan, carboplatin) is delivered directly into the ophthalmic artery via selective catheterization, achieving high intraocular drug concentration while minimizing systemic toxicity. **Advantages:** - Superior response rates for Groups A–D tumours (80–90% eye salvage) - Minimal systemic toxicity compared to intravenous chemotherapy - Allows monitoring of response and escalation if needed - Preserves vision in responsive eyes **Clinical Pearl:** IAC is now the preferred first-line chemotherapy for intraocular retinoblastoma in specialized centres. It has largely replaced external beam radiotherapy (EBRT) as primary treatment because EBRT increases risk of secondary malignancies in the radiation field, especially in bilateral disease where the contralateral eye is at risk. ### Why Other Options Are Suboptimal **Bilateral Enucleation:** - Results in permanent blindness (child becomes blind) - Unnecessary for Groups B–C tumours, which have excellent salvage rates with chemotherapy - Reserved only for eyes that fail chemotherapy or have advanced disease (Group E) - Violates the principle of vision preservation in paediatric oncology **External Beam Radiotherapy (EBRT):** - Increases risk of secondary malignancies (osteosarcoma, soft-tissue sarcoma) in the radiation field - Risk is especially high in bilateral disease and in young children - Now reserved for eyes that fail chemotherapy or have optic nerve involvement - Has been largely replaced by IAC as primary treatment **Intravitreal Chemotherapy (IVC):** - Used as an adjunct for vitreous seeding or recurrent disease - NOT primary treatment for intraocular tumours - Penetration is limited to the vitreous cavity; does not reach the tumour base effectively - Risk of retinal toxicity with repeated injections **High-Yield:** The modern paradigm for retinoblastoma is **chemotherapy-first** (IAC or systemic) with close monitoring. Radiation and enucleation are reserved for chemotherapy failures or advanced disease. ### Management Algorithm for This Case 1. **Initiate IAC** to both eyes (melphalan-based regimen, typically 3–4 cycles) 2. **Assess response** at 6–8 weeks with imaging (ultrasound, MRI) and dilated fundoscopy 3. **If good response:** Continue IAC or transition to observation with close follow-up 4. **If poor response (Group C eye):** Add external beam radiotherapy or consider enucleation 5. **If excellent response (Group B eye):** Continue observation; enucleation only if recurrence **Mnemonic: CHEMO-FIRST** — **C**hemotherapy (IAC/systemic) first; **H**igh salvage rates (80–90%); **E**nucleation reserved for failures; **M**onitoring essential; **O**bservation long-term; **F**irst-line avoids EBRT toxicity; **I**ntraocular disease; **R**adiation second-line; **S**alvage vision; **T**reatment individualized. [cite:Boyd & Melia Retinoblastoma; Murphree et al., Retinoblastoma in Pediatric Oncology; AIIMS Ophthalmology protocol]