The existence of a luminal B/HER2-negative subtype in breast cancer may triple the risk of ipsilateral breast tumor recurrence (IBTR) among patients with breast cancer who undergo breast-conserving surgery (BCS) with or without postsurgical radiotherapy (XRT), according to a study published in The Breast.1

Previous studies have demonstrated that intrinsic subtypes are associated with distant recurrence of breast cancer as well as IBTR. How XRT after surgery modifies IBTR risk among different subtypes however, requires further investigation. 

For this study, investigators randomly assigned 381 women with T1N0M0 breast cancer to undergo BCS with or without postoperative XRT. Modern immunohistochemical methods were used to evaluate available histopathological material in 223 women. The risk of IBTR according to breast cancer subtypes was assessed; subtypes that were evaluated were luminal A, luminal B/HER2-negative, luminal B/HER2-positive, HER2-positive, and triple negative. The follow-up period was 20 years. 

Results of a multivariate analysis revealed that the luminal B/HER2-negative subtype was associated with higher IBTR risk overall (hazard ratio [HR], 3.04; 95% CI, 1.38 to 6.71) and in both the XRT group (HR, 2.58; 95% CI, 1.07 to 6.20) and the group without XRT (HR, 5.08; 95% CI, 1.31 to 19.7) (P= .37). 

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Further analysis revealed that XRT led to an absolute risk benefit at 20 years for the luminal A (14%; 95% CI, 1.0 to 26); luminal B/HER2-negative (17%; 95% CI, -6.0 to 39); and HER2-positive and triple negative (high-risk; 22%; 95% CI, -7.0 to 51) subtypes compared with non-XRT groups. 

Although findings showed that luminal B/HER2-negative status may be predictive for IBTR, the authors added that they were unable to confirm which subtypes would benefit most from  XRT. 

They concluded that their findings may contribute to an understanding of “the associations between intrinsic subtypes and clinical outcomes, but calls for further research to understand the risk of IBTR for the different intrinsic subtypes with or without adjuvant radiotherapy.”

Reference

  1. Wickberg A, Magnuson A, Holmberg L, Adami H-O, Liljegren G. Influence of the subtype on local recurrence risk of breast cancer with or without radiotherapy[published online August 21, 2018]. Breast. doi: 10.1016/j.breast.2018.08.097