Relationship of regression pattern to recurrence in retinoblastoma.

A retrospective analysis has been conducted of regression patterns following treatment of retinoblastoma by external beam irradiation. There were 180 tumours in 105 eyes of 83 patients. Type I regression was found to be the commonest pattern and occurred in 50% of cases. Initial tumour size was found to be the only statistically significant determinant of regression pattern (p < 0.01). Thirteen tumours (7%) recurred within a median interval to recurrence of 12 months. All recurrences occurred within 40 months of completion of treatment and none occurred after age 4 years. No tumour less than 6 mm in diameter recurred. Although 10 out of 13 recurrences were of Type I, Cox model regression analysis showed initial tumour size to be the only independent predictor of recurrence (p < 0.01).