Physicians may be able to predict which patients with HER2-positive breast cancer can safely forgo surgery based on tumor hormone status, imaging results after neoadjuvant chemotherapy and ductal carcinoma in situ on initial biopsy, according to study results presented at American Society of Breast Surgeons Annual Meeting.
“HER2-positive breast cancer makes up about 20% of breast cancers in the United States per year, and these tumors have shown to be highly responsive to chemotherapy, especially with the addition of targeted anti-HER2 therapies,” Susie Sun, MD, breast surgery oncology fellow at The University of Texas MD Anderson Cancer Center, said during a webcast. “When pathologists see no residual cancer in the surgical specimen after neoadjuvant chemotherapy, they call this a pathologic complete response [PCR]. The high rates of PCR seen in HER2-positive breast cancer highlight the potential for omission of surgery in this cohort after neoadjuvant systemic therapy.”
Sun and colleagues analyzed 280 patients with clinical T1-2N0-1 HER2-positive breast cancer treated with neoadjuvant systemic therapy prior to surgical resection.
Identifying clinical characteristics associated with residual disease after neoadjuvant systemic therapy served as the study’s primary endpoint. The effect of neoadjuvant systemic therapy on invasive and DCIS components of HER2-positive breast cancer served as secondary endpoints.
Of the 280 patients, 102 (36.4%) achieved PCR in the breast and lymph nodes after neoadjuvant systemic therapy. Fifty patients (17.9%) had residual DCIS in the breast only after neoadjuvant systemic therapy.
Patients with residual disease in the breast and nodes appeared more likely to have hormone receptor-positive tumors (73.4%) vs. negative tumors (50.8%; P < .0001).
Incomplete radiologic response (OR = 5.62; P = .002) and hormone-positive status (OR = 2.56; P < .0001) both served at variables predictive of residual disease.
DCIS appeared on the initial biopsy of 129 patients (46.1%). Thirty-two of these patients (24.8%) had residual DCIS only following neoadjuvant systemic therapy. Thus, therapy failed to eradicate in situ disease in 64.3% of patients.
Patients with DCIS were less likely to achieve PCR in the breast than patients without DCIS (31% vs. 43%; P = .038).
MRIs, mammograms and ultrasounds after neoadjuvant systemic therapy had a sensitivity of 97.1% (95% CI, 95.1-99.1) and a negative predictive value of 70.6% (95% CI, 65.1-76) in detecting residual disease in the breast and lymph nodes.
“Our study found that identifying DCIS as a component of the invasive cancer for HER2-positive breast cancer decreases the relative chance of PCR by 30%,” Sun said. “For the currently accruing trial evaluating the safety of eliminating surgery for patients who are exceptional responders to neoadjuvant systemic therapy, eradication of both the invasive and DCIS components are necessary because DCIS may [cause] carcinoma in the future.” – by John DeRosier
Reference: Sun S, et al. Patient selection for non-operative management of HER2-positive invasive breast cancer after neoadjuvant systemic therapy. Presented at: American Society of Breast Surgeons Annual Meeting; April 30-May 5, 2019; Dallas.
Disclosures: HemOnc Today could not confirm the authors’ relevant financial disclosures at the time of reporting.