SAN ANTONIO – compared with White women, a discovery that may at least partially explain racial differences in breast cancer outcomes, investigators say.
The finding, which comes from a retrospective study comparing differences in tumor microenvironment of metastasis (TMEM) “doorways” between Black and White women suggest that tumors in Black women may have a stronger prometastatic response to neoadjuvant chemotherapy than tumors in White women, reported Maja H. Oktay, MD, PhD, of Montefiore Einstein Cancer Center, Albert Einstein College of Medicine, New York, at the San Antonio Breast Cancer Symposium.
“Looking forward ... we propose to use TMEM doorway density as a prognostic marker for distant recurrence-free survival as a marker of dissemination, and also as a predictive marker of response to drugs that can block TMEM doorways,” she said at a briefing held prior to the presentation of data in an oral abstract session.
As their name implies, TMEM doorways are transient entry points or portals that allow cancer cells to disseminate to distant sites. TMEM doorways are composed of tumor cells, macrophages, and endothelial cells that come into direct contact and together create temporary vascular openings that allow tumor cells to cross cell walls into circulation, where they can then hitch a ride and travel to distant organ sites.
Previous studies have shown that TMEM doorway density is a prognostic marker of metastasis in breast cancer patients treated with adjuvant chemotherapy. And as Dr. Oktay and colleagues showed in the current study, TMEM doorway density, as measured by a TMEM doorway score, is a prognostic marker for distant metastatic recurrence of ER+/HER2– breast cancer following neoadjuvant chemotherapy.
They also showed that neoadjuvant chemotherapy may increase the TMEM doorway score and lead to a pro–metastatic tumor microenvironment in some women.
The investigators measured TMEM doorway scores from residual breast cancers in women who had undergone standard neoadjuvant chemotherapy. The cohort consisted of 96 Black women, 43 of whom had ER+/HER2– breast cancer and 37 of whom had triple-negative breast cancer (TNBC), and 87 White women, 50 with ER+/HER2– cancer and 22 with TNBC. The remaining patients had other breast cancer subtypes.
They found that TNBCs had higher TMEM doorway density score and higher macrophage density scores, which may explain why patients with TNBC often have early recurrence of disease.
They also found that, compared with White patients, Black patients with ER+/HER2– tumors, but not TNBC tumors, had higher TMEM doorway density scores. Similarly, Black patients with ER+/HER– cancers, but not TNBC, had higher macrophage levels than White women, a finding that may explain racial disparity in ER+/HER2– disease, Dr. Oktay said.
For the entire cohort, patients with high TMEM doorway density scores had significantly worse distant recurrence–free survival than patients with intermediate or low scores (P = .008), and there was a trend toward worse DRFS among all patients with ER+/HER2– who were in the highest third of scores, but this did not quite reach statistical significance.
High versus low TMEM doorway density score was also an independent prognostic factor for worse outcomes among the entire cohort (P = .01).
There was no significant difference in TMEM density scores among patients with TNBC.
Neither high macrophage counts nor microvascular density alone were significantly associated with inferior DRFS. TMEM doorway score was the only factor significantly prognostic for worse outcomes among patients in the entire cohort.