Influence of the subtype on local recurrence risk of breast cancer with or without radiotherapy

Breast Cancer Subtype May Be Predictive of Ipsilateral Breast Tumor Recurrence

Studies have shown that certain intrinsic subtypes of breast cancer are associated with a higher propensity for distant as well as ipsilateral breast tumor recurrence (IBTR). The question that still seems to remain is how are those subtypes affected by radiation?

A study recently published in The Breast  followed 381 women for 20 years who had breast conserving surgery (BCS)  with or without post-op radiation therapy; each also had their tumors sub-typed.  In a multivariant analysis, they found that with or without radiation therapy , luminal B/HER2-negative subtype may triple the risk of IBTR.

In all subtypes, there was some benefit from radiotherapy that moderated the IBTR. See table below

Absolute Risk Benefit from Radiation Therapy by Subtype After BCS

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

The authors also concluded that their findings may contribute to an understanding of “the associations between intrinsic subtypes and clinical outcomes”, “but further research is required to determine the risk of IBTR for the different intrinsic subtypes with or without adjuvant radiotherapy.”

TME Commentary by Peter Beitsch, MD FACS
Breast cancer subtypes carry very different prognoses related to their ability to metastasize distantly leading to decreased survival.  Therefore it is not surprising that different subtypes have different incidences of local-regional recurrences.  This has also been shown in genomic tests - OncotypeDX and MammaPrint - where higher Recurrence Scores (OncotypeDX) or high risk tumors (MammaPrint) have higher incidences of local regional recurrences.  

Bad tumors behave badly systemically AND local-regionally.