Author: By Lynda Williams, Senior medwireNews Reporter
medwireNews: Over half of women with HER2-positive invasive breast cancer with a ductal carcinoma in situ (DCIS) component achieve a complete response to neoadjuvant systemic therapy, shows a Dutch nationwide analysis presented at the European Breast Cancer Conference 2022 in Barcelona, Spain.
The findings confirm earlier studies that have countered the hypothesis that DCIS is less responsive to systemic therapy than invasive disease and requires mastectomy, reported presenting author Roxanne Ploumen, from Maastricht University in the Netherlands.
The researchers collated information from the Netherlands Cancer Registry for all 5834 women who received chemotherapy and/or targeted therapy before surgery between 2010 and 2020 and had available pathology reports for biopsies taken before neoadjuvant therapy and after surgery.
The majority (75.3%) of women did not have any sign of DCIS in their biopsy before neoadjuvant therapy, but it was detected in 25.7% of these patients after surgery. Moreover, 24.7% of women had DCIS in their pretreatment biopsy; of these 1443 patients, 48.5% continued to have DCIS present in their postoperative biopsy and 51.5% did not.
Thus, the complete response rate of the pre-existing DCIS component after neoadjuvant treatment was 51.5%, and this outcome was significantly more common in patients who also had complete response in their invasive tumour than those who did not (63.4 vs 33.8%), reported Roxanne Ploumen.
Women were significantly more likely to achieve DCIS complete response if they had received chemotherapy plus targeted therapy versus chemotherapy alone, with an odds ratio of 5.97 after adjusting for age, invasive breast cancer status, grade and oestrogen receptor (ER) status, as well as DCIS grade, comedonecrosis and calcifications.
Women with ER-negative invasive breast cancer were also 1.80 times more likely to achieve DCIS complete response than their ER-positive counterparts in this multivariable analysis, the presenter said.
Finally, Roxanne Ploumen noted that women with a DCIS component in their pretreatment biopsy were significantly more likely to undergo mastectomy than those whose invasive breast cancer did not include DCIS, at rates of 53.6% versus 41.0%.
Therefore, the clinical impact of the results was “still less breast conserving surgery is performed in patients with a DCIS component despite a potential response”, she summarised.
The presenter concluded that further research is required to confirm these findings and allow them to be considered in daily clinical practice.
Ploumen R, Claassens E, Kooreman L, et al. Complete response of ductal carcinoma in situ to neoadjuvant systemic therapy in HER2-positive invasive breast cancer patients: a nationwide analysis. Eur J Cancer 2022;175(Supplement 1): S1. DOI: https://doi.org/10.1016/S0959-8049(22)01350-8
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