Borderline ER-Positive Primary Breast Cancer Gains No Significant Survival Benefit from Endocrine Therapy
Endocrine responsiveness of primary breast cancers with borderline ER (1%-9%) is unclear. Both ASCO and College 0f American Pathologists recommend that ER be defined as greater than 1% of all tumor cells with positive staining using IHC. And yet intuitively and based on anecdotal experience, it would seem reasonable to assume that patients with low ER values would not respond as well to endocrine therapy as those with higher ER values. Chen et all (authors from both the US and China) have attempted to solve this paucity of data by publishing a large meta-analysis exploring this very topic (Chen et al).
They retrieved eligible literature from the inception of PubMed through November 2016. There were 3 cohorts: ER-, ER+ 1-9% and ER+>9%. The analysis included 6 studies with 16,606 patients. When analyzing ER+ (1-9%), no significant differences were noted in the 5-year DFS among patients who received endocrine therapy with low ER+ and those with ER negative tumors. In distinction, patients with ER+ (>10%) manifested a significantly better prognosis in terms of 5-year DFS than those in the ER+ (1-9%) group.
Comment: The results of this study come as no surprise. Despite that, it is unclear to me after slogging through this paper whether the contention in the title of the paper has in fact been proven. I found the statistical evaluation overwhelming likely reflecting my poor aptitude in this conjunction of math and medicine. I shall be interested in comments by those much more versed in the statistical evaluation of this paper.