Postmastectomy Radiation and Recurrence Patterns in Breast Cancer Patients Younger Than Age 35 Years: A Population-Based Cohort

Background. The utility of post mastectomy radiotherapy in very young women is understudied. The objective of this study was to evaluate the use of PMRT in very young women to determine the effect on recurrence and survival. Methods. All women aged <= 35 years diagnosed with invasive breast cancer from 1994 to 2003 were identified from the Ontario Cancer Registry. Patient, tumour, treatment and outcome data were abstracted from primary chart review. Local or regional recurrence was the primary endpoint with contralateral, distant recurrence/death treated as competing risks. Propensity score methods were incorporated into multivariable Cox proportional hazards models to evaluate the effect of radiation therapy on the time to local/regional, distant recurrence or death. Results. 588 patients were identified during the study period, of which 382 were eligible for analysis. Overall, 182 (48 %) of patients sustained a recurrence after a median follow-up of 2.72 years. The use of PMRT significantly reduced locoregional recurrence (HR 0.54, 95 % CI 0.29-0.996) compared with those who did not receive PMRT. There was no significant effect of PMRT on contralateral, distant recurrences, or death without recurrence (HR 0.98, 95 % CI 0.66-1.47). Of the patients with known node status (N = 451), isolated local recurrence occurred in 5, 2.5, and 8.5 % in patients with N0, N1-3, and N4 positive nodes respectively. Conclusions. We have found a significant reduction in locoregional recurrence with PMRT but no survival benefit in very young women with breast cancer.