A new approach to the classification of breast cancer patients that recognises intrinsic biological subtypes has been recommended by the St Gallen expert panel, reports the Annuals of Oncology.

The 51 member strong expert panel, which met at the 12th International Breast Cancer Conference held at St Gallen (Switzerland) in March2011, said that for practical purposes these subtypes may be approximated using clinicopathological rather than gene expression array criteria.  The Panel was charged with assessing the evidence, and providing expert opinion on those questions where the evidence was ambiguous or lacking.

The expert panel, led by Aron Goldhirsch, from the European Institute of Oncology (Milan, Italy), identified four subtypes of breast cancer according to oestrogen and progesterone receptors, over expression and/or amplification of the human epidermal growth factor receptor 2 (HER2) oncogene, and the Ki-67 labelling index as a marker of cell proliferation.

 The four subtypes were luminal A, luminal B, Erb-B2 over expression and basal like. The expert panel provided systemic treatment recommendations for the subtypes including endocrine therapy alone  for luminal A, endocrine +_ cytotoxic therapy for Luminal B (HER2 negative);  cytotoxics + anti-HER2 + endocrine therapy for  ‘Luminal B (HER2 positive); cytotoxics + anti-HER2 for ‘HER2 positive (non luminal);  and cytotoxics for ‘Triple negative (ductal)’.

“The approach to treatment within breast cancer subtypes greatly simplifies the definition of therapy indications, since the subtypes themselves incorporate many of the risk and predictive factors used in previous consensus recommendations,” write the authors.

Additionally the panel was clearly of the view that the routine use of immunohistochemistry to look for low-volume metastatic disease in sentinel nodes was not indicated since metastases shown only by immunohistochemistry would not alter management

The Panel was however divided about the use of accelerated whole-breast radiotherapy in the presence of extensive vascular invasion. By a slim majority they voted in favour of post-mastectomy radiation for patients younger than 45 years with 1-3 positive nodes and for patients at any age with extensive vascular invasion in two or more blocks in conjunction with 1 to 3 positive nodes.

Reference 

A Goldhirsch, WC Wood, AS Coates et al. Strategies for subtypes – dealing with the diversity of breast cancer: highlights of the St Gallen International Expert Consensus on the Primary Therapy of Early Breast Cancer 2011.  Annals of Oncology.  Doi:10.1093/annonc/mdr304.