medwireNews: Men are less likely than women to achieve a pathologic complete response (pCR) to neoadjuvant chemotherapy for invasive, nonmetastatic breast cancer, US researchers report.
And finding that pCR is prognostic for overall survival (OS) in both men and women, the investigators suggest that “pCR may serve as an end point for clinical trials in [male breast cancer], which is a rare disease, and facilitate the identification of effective therapies using smaller sample sizes.”
José Pablo Leone (Dana-Farber Cancer Institute, Boston, Massachusetts) and co-workers collated information from the US National Cancer Database for 385 cases of male breast cancer and 68,065 cases of female breast cancer who underwent neoadjuvant chemotherapy.
The men were significantly older than the women, and had a significantly lower tumor grade and higher clinical stage than the women.
There was also a significant difference in the distribution of tumor subtypes between men and women, the researchers observe.
Specifically, 53.5% of men had hormone receptor (HR)-positive, HER2-negative disease compared with 37.2% of women, and there were differences in the rates of HR-positive, HER2-positive (29.1 vs 22.8%), HR-negative, HER2-positive (6.5 vs 12.0%), and triple-negative (10.9 vs 27.9%) disease.
The men received neoadjuvant chemotherapy a median 31 days after diagnosis and underwent surgery a median 143 days after beginning their regimen; the corresponding median times for women were 30 days and 148 days. Men were significantly more likely than women to undergo mastectomy (81.0 vs 63.8%).
The rate and likelihood of pCR was lower in men than women regardless of tumor subtype and this difference reached statistical significance for those with HR-positive, HER2-positive disease, with pCR rates of 16.1% versus 33.6% and an odds ratio for pCR of 2.6 in favor of the women.
After taking into consideration patient characteristics, tumor subtype, and other features, women were twice as likely to achieve pCR as men, say Leone and co-authors in Cancer.
In addition, men were less likely to achieve complete clinical response to neoadjuvant chemotherapy than women (13.5 vs 23.3%) and significantly more likely to have no clinical response (10.6 vs 5.0%).
The team also assessed the impact of pCR and sex on OS for 297 men and 53,826 women with available information on survival for a median 33 and 35 months of follow-up, respectively.
There was a significantly higher 5-year rate of OS among men with a pCR than those without (90.0 vs 64.7%) and this was also true for women with versus without a pCR (91.9 vs 75.3%).
Although univariate analysis suggested men had a poorer 5-year OS than women overall (67.1 vs 79.0%), there was no significant difference when looking at only men and women with a pCR (90.0 vs 91.9%) and multivariate analysis confirmed that there was no significant difference overall in OS between the men and women.
The researchers note that their study was limited by the small numbers of men with some tumor subtypes and the lack of detailed information on the neoadjuvant chemotherapy regimens received by the study cohorts.
Nevertheless, they emphasize that the lower likelihood of pCR in men than women “is a provocative finding and warrants further research in men with residual disease to improve outcomes.”
Leone et al conclude: “The results from our study are valuable to inform about the comparative efficacy of [neoadjuvant chemotherapy] between men and women with breast cancer, given that there has never been a prospective trial evaluating the efficacy of [neoadjuvant chemotherapy] in [male breast cancer], and there are no prospective comparisons of the efficacy of [neoadjuvant chemotherapy] between sexes.”
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Cancer 2022; doi:1002/cncr.34448