Introduction: There has previously been controversy regarding the benefits of post-mastectomy radiotherapy (PMRT) for women with breast cancer (BC) who have tumours less than 5cm (T1-2) and one to three positive lymph nodes (N1). In 2014, the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) published a meta-analysis showing that PMRT reduced recurrence and breast cancer mortality in these women. International clinical guidelines were subsequently updated however, no changes have yet been made to Australian guidelines.
Aims: To describe patterns of care of PMRT in patients with T1-2 N1 breast cancers before and after 2014 and identify predictors for the receipt of PMRT.
Methodology: This was a retrospective institutional study of women with newly diagnosed BC from 2011-2016. Univariate and multivariate regression testing were performed to identify factors associated with receipt of PMRT and establish treatment related trends over time.
Results: 236 patients were identified with a median age of 56 years. Two-thirds were post-menopausal at diagnosis. 75% of tumours were Invasive Ductal carcinoma, 41% were high grade, and 36% were multifocal. Lymphovascular Invasion (LVI) was seen in 52% of cases and 22% had 3 positive lymph nodes (LN). 70% of patients had chemotherapy, 16.5% had Herceptin and 85% had endocrine therapy. 72% of patients received PMRT, 16% declined PMRT, in 12% it was not recommended and 2% did not have PMRT discussed or documented. 70% and 71% received PMRT from 2011-2013 and 2014-2016 respectively (p=NS). On multivariable analysis, patients with larger tumours, LVI, multifocal tumours, 3 positive LNs and younger age were significantly more likely to receive PMRT.
The utilisation of PMRT in this population was high and no further increase was noted following publication of the EBCTG meta-analysis suggesting that this did not influence practice over the time period studied.