Objective: To evaluate retinoblastoma regression patterns following chemoreduction and adjuvant therapy.
Participants: A total of 557 retinoblastomas.
Methods: A retrospective medical record review following 6 cycles of chemoreduction and tumor consolidation (thermotherapy or cryotherapy). Regression patterns included type 0 (no remnant), type 1 (calcified remnant), type 2 (noncalcified remnant), type 3 (partially calcified remnant), and type 4 (flat scar).
Main outcome measures: Regression pattern.
Results: Retinoblastoma regressions were type 0 (n = 10), type 1 (n = 75), type 2 (n = 28), type 3 (n = 127), and type 4 (n = 317). Tumors with an initial thickness of 3 mm or less regressed most often to type 4 (92%), those 3 to 8 mm regressed to type 3 (34%) or type 4 (40%), and those thicker than 8 mm regressed to type 1 (40%) or type 3 (49%). Factors predictive of type 1 regression included larger tumor base and closer foveolar proximity. Factors predictive of type 3 included older age, larger tumor base, macular location, closer foveolar proximity, and lack of consolidation. Factors predictive of type 4 included familial hereditary pattern, smaller tumor base, greater foveolar distance, and tumor consolidation.
Conclusions: Following chemoreduction, most small retinoblastomas result in a flat scar, intermediate tumors in a flat or partially calcified remnant, and large tumors in a more completely calcified remnant.