Many TNBC Patients Unnecessarily Opt for Mastectomy

The use of neoadjuvant systemic chemotherapy increases the percentage of women with triple-negative breast cancer (TNBC) who are eligible for breast-conserving therapy, yet many women still opt for mastectomy, according to an international randomized trial presented at the American Society of Clinical Oncology (ASCO) Annual Meeting (abstract 514).

Neoadjuvant systemic therapy has been shown to increase the frequency of breast-conserving therapy among women with stage II to III breast cancer who are deemed eligible only for mastectomy, but “little data exist on how often neoadjuvant systemic therapy converts TNBC patients initially deemed ineligible to eligible for breast-conserving therapy,” said lead author Mehra Golshan, MD, associate professor of surgery at Harvard Medical School. No data exist on surgical management and patient decision making when genetic information is made available to the patient at the onset of neoadjuvant systemic therapy.

Golshan and colleagues collected surgical assessment and management data on neoadjuvant systemic therapy in TNBC patients to examine the impact on conversion to breast-conserving therapy.

Some 604 patients, median age 51 years, with operable TNBC were randomized to veliparib 50 mg orally twice daily with carboplatin AUC 6 mg/ml/min every 3 weeks and paclitaxel 80 mg/m² weekly for 12 weeks followed by doxorubicin and cyclophosphamide for 4 cycles; placebo with carboplatin and paclitaxel; or placebo with paclitaxel followed by doxorubicin and cyclophosphamide for 4 cycles.

The surgeons used clinico-radiographic criteria before and after neoadjuvant systemic therapy to assess whether the women were candidates for breast-conserving therapy. Surgical management was at surgeon and patient discretion.

The researchers assessed interactions between breast-conserving therapy eligibility pre- and post-neoadjuvant therapy, germline BRCA mutation status, pathologic complete response (pCR), and whether patients received mastectomy or breast-conserving therapy.

Among the 599 patients with eligible assessments, neoadjuvant systemic therapy increased breast-conserving therapy eligibility from 76% to 84%. Of 141 patients deemed ineligible at baseline, 75 patients converted to eligible, but only 56% of these women opted for breast-conserving therapy.

The pCR rates were virtually identical between eligible patients who chose breast-conserving therapy (55%) and those who chose mastectomy (53%). The pCR rates were 49% in eligible converts and 36% in those who remained ineligible.

The 85 patients with germline BRCA mutations were less likely to choose breast-conserving therapy, even if they were eligible, Golshan said.

Patients treated in North America were less likely to choose breast-conserving therapy (55%) than those in Europe and Asia (80%), even among non–germline BRCA patients considered eligible after neoadjuvant systemic therapy (61% vs 86%).

Despite the increase in eligibility for breast-conserving therapy, “one-third of women still underwent mastectomy,” reported Golshan. “Although pCR rates were higher in patients who were eligible for breast-conserving therapy after neoadjuvant systemic therapy, one-third of ineligible patients were found to have achieved a pCR.”

“Patients treated in North America who underwent mastectomy were also much more likely to undergo contralateral prophylactic mastectomy, even among those without an identified predisposition to development of contralateral breast cancer. These findings are concerning,” noted Golshan.