Radiation after Breast-conserving Surgery Reduces Cancer Recurrence
A long-term follow up analysis of a trial has shown that breast radiation following lumpectomy significantly reduces incidence of ipsilateral breast recurrence (IBR) for “low risk” DCIS.
NRG-RTOG 9804 is a clinical study conducted by the National Cancer Institute National Clinical Trials Network group NRG Oncology. These results were recently published in JCO.
IBR occurs at a rate of 5-10% after breast-conserving surgery. The NRG-RTOG 9804 study enrolled 636 women with a median age of 58 between December 1999 and July 2006. Patients were randomised to breast radiation (RT) or observation (OBS) treatment groups. All patients who participated in the trial underwent annual mammography and specified clinical exam intervals. For this analysis, the median follow up time was 13.9 years.
Analysis focused on the long-term cumulative incidence of IBR, the primary endpoint in the study. The study hypothesised that radiation would significantly reduce IBR from 6% to 3.5% at 5 years, assuming that the reduction in IBR from RT would be less than previous trials that included higher grades and larger sizes of DCIS. With long-term follow-up, cumulative incidence of IBR remained statistically significantly lower with RT, as compared to OBS. At 10 and 15 years, the cumulative incidence of IBR with OBS was 9.2% and 15.1%, respectively, and was 1.5% and 7.1%, respectively, with RT. The 10 and 15 year invasive IBR incidence, respectively, was 0.4% and 5.4% with RT; 4.3% and 9.5% with OBS. A total of 52 IBRs were observed; 14 in the RT arm and 38 in the OBS arm.
No statistically significant differences in mastectomy, distant metastasis, overall or disease-free survival were seen between the two treatment arms.
“Since IBR risk continues to increase through at least 15 years, with radiation conferring both a delay and decrease in this risk, the data presented support the decision to treat patients who wish to minimise their IBR and particularly the invasive cancer risk long term. Factors such as age, life expectancy, and willingness (if oestrogen receptor–positive) to take antioestrogen therapy should be taken into consideration in this patient-doctor shared decision,” stated lead author Beryl McCormick, MD, of the Memorial Sloan Kettering Cancer Center.
Source: NRG Oncology
