Collins' law revisited: can we reliably predict the time to recurrence in common pediatric tumors?

Collins' law states that the period of risk for tumor recurrence is the age of the child at diagnosis plus 9 months. The purpose of this study is to validate this rule through a retrospective review of common pediatric tumors seen at 1 institution. Inclusion criteria for this study included an age at diagnosis of < 16 years old, minimum follow-up time of the Collins risk period (CRP) if child did not relapse and treatment with curative intent. The records of 424 children seen and treated for neuroblastoma (n = 98), Wilms tumor (n = 86), rhabdomyosarcoma (n = 82), medulloblastoma (n = 59), Ewing sarcoma (n = 43), ependymoma (n = 25), supratentorial PNET (n = 22), and synovial sarcoma (n = 9) from 1960 to 2001 were reviewed. CRP was calculated using the age of child at initial diagnosis plus 9 months. The median follow-up time was 164 months (range, 11-484 months), while the median follow-up/CRP ratio was 4.89 (range, 1.0-48.0). A total of 183 of 424 (43.2%) patients relapsed, with 180 (98.4%) relapses occurring during the CRP. Relapses beyond the CRP were seen in 3 young children (ages 7 months, 24 months, and 2 weeks at initial diagnosis) with a diagnosis of Wilms tumor (n = 2) and supratentorial PNET (n = 1) at 1, 3, and 26 months post-CRP. Collins' law is a useful and simple way of predicting risk period for relapse in the tumor types studied.