Leone et al show molecular subtypes in #malebreastcancer and that they determine outcome

Prognostic significance of tumor subtypes in male breast cancer: a population-based study

Leone JP, Leone J, Zwenger AO, Iturbe J, Vallejo CT, Leone BA.

Breast Cancer Res Treat. 2015 Jul 1. [Epub ahead of print]

Background

This paper investigates whether the outcomes for men with breast cancer are determined by the sub-type of breast cancer they have, which is the case for women. We know that for women the expression of Her-2 or the complete absence of hormone receptors and Her-2, so called triple negative, are both associated with worse outcomes. While the same subtypes of breast cancer occur in men, whether they influence outcomes is not yet clear. A study by Chavez-Macgregor in 2013 of a cohort of around 600 men in California, failed to show a strong impact of subtype on outcome. Now Leone et al. are using the SEER data from NCI to take a look at this question.

Findings

Leone et al studied 960 men who were diagnosed with breast cancer between 2010 and 2012, and followed them for a median of 15 months. They found the following distribution of subtypes:

  • 85% hormone receptor (HR; estrogen and progesterone receptor) positive, HER2-negative
  • 12% HR-positive, HER2-positive
  • less than 1% HR-negative, HER2-positive
  • 3% triple negative

This distribution is similar to what has been shown before by Chavez-Macgregor et al.

The authors measured overall survival at 2 years, and found that across the entire cohort, 91% were still alive at that point. However, the two rarest subtypes showed significantly lower 2-year overall survival rates:

  • triple negative 78%
  • HR-negative, HER2-positive 80%

When comparing patients with HER2 against those without, the authors also saw that an impact:

  • HER2-positive 85%
  • HER2-negative 92%

Comment

The findings made in this paper suggest that the molecular subtypes influence outcome in male breast cancer just like in female breast cancer, and with the same trends: hormone receptor expression is associated with relatively better outcomes, HER2 expression or the complete absence of any of the markers with worse outcomes. This is not surprising, perhaps, but it is also very important to have investigated it and now to have evidence for it.

There is evidence in women’s breast cancer that these marker differences are associated with differences in the biology of the tumors – something that remains to be seen in men. However, the evidence provided by Leone et al is a good indicator that it is also true in men. This would in turn suggest that biological similarities between the men’s and the women’s disease predominate, at least in terms of outcome.

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