Secondary Prevention of Retinoblastoma Revisited: Laser Photocoagulation of Invisible New Retinoblastoma.

Purpose: Invisible retinoblastoma tumors are now detected with screening for retinal tumors in at-risk neonates (those inheriting RB1 pathogenic alleles from affected parents) using handheld OCT. Laser photocoagulation is challenging, requiring exact localization of a tumor invisible to indirect ophthalmoscopy and standard imaging. We describe OCT-guided localization and photocoagulation of these invisible tumors with 1-year follow-up.

Design: Retrospective, noncomparative, single-institutional, observational case series.

Participants: Children with any clinically invisible retinoblastoma tumor that was detected on OCT posterior pole screening.

Methods: OCT revealed round homogeneous invisible tumors within the inner nuclear layer. Software calipers placed beside anatomic retinal landmarks (branched/curved vessels, fovea, or optic disc) mapped the tumor location and extent. A single laser (532 nm) burn flagged the location, and OCT evaluated the tumor-laser burn relationship; laser treatment was then continued in the correct location. Post-laser OCT ensured complete treatment.

Main Outcome Measures: Accuracy (frequency of geographic miss and skip areas), effectiveness (recurrence rate), and burden (scar size and characteristics at final follow-up) of laser treatment.

Results: Eleven new invisible posterior pole tumors in 7 eyes of 5 children were treated by this technique. Localization and tumor-laser burn relationships were accurate in 11 of 11 tumors (100%, 95% confidence interval [CI], 49.9-100), and all showed swelling and hyper-reflectiveness of the tumor in post-laser OCT. Two photocoagulation sessions (2 weeks apart) were sufficient to successfully manage 9 of 11 tumors (82%, 95% CI, 37.4-100) with resulting permanent flat scars. One tumor (9%, 95% CI, 0.2-50.6) developed OCT-detected subclinical recurrences within 3 months, treated by 1 laser session. No treatment scar showed gliosis, foveal involvement, or retinal traction at 1-year follow-up. Scar expansion occurred in 1 tumor (9%, 95% CI, 0.2-50.6), and all scars (100%, 95% CI, 49.9-100) showed pigmentary changes.

Conclusions: The OCT-guided localization and photocoagulation technique is valuable in achieving precision results in managing invisible new retinoblastoma tumors. This technique shows a potential to improve outcomes of secondary prevention screening for retinoblastoma.