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Top Line: Receptor status is a crucial predictive and prognostic biomarker for breast cancer.

The Study: But is the progesterone receptor (PR) crucial, really? Sure, sometimes we say “ER/PR-positive,” but most of the time we think of breast cancer as either hormone receptor-positive or not. This SEER analysis of over 800K patients with breast cancer and known receptor status sought to establish how just how much the PR-status matters. Of these cases, two-thirds were ER/PR(+), 19% ER/PR(-), 12% ER(+)/PR(-) and <2% the elusive ER(-)/PR(+)—though the latter cohort comprises the largest of its kind on record. As expected, the ER/PR(-) cases fared the worst, which is why they aren’t treated anything like hormone receptor-positive cases. Most interesting is figure 3 that graphs the primary endpoint of breast cancer-specific survival (BCSS) for all subsets, with mean BCSS for ER/PR(+) cases soaring 20 months ahead of ER(+)/PR(-) cases (HR 1.4) and 28 months beyond that of ER(-)/PR(+) cases (HR 1.6). As confirmation, when compared to one another, BCSS was significantly higher for ER(+)/PR(-) cases than for ER(-)/PR(+). But should we really be surprised considering they all likely received ER-targeted therapies?

TBL: The more hormone receptor-positivity the better, meaning those with ER(+)PR(-) and especially ER(-)/PR(+) breast cancers may be deserving of their own more aggressive treatment algorithms. | Li, JAMA Netw Open 2020