This patient should receive neoadjuvant trastuzumab-based chemotherapy. Disease-free survival and overall survival are equivalent in patients treated with neoadjuvant and adjuvant chemotherapy. However, neoadjuvant chemotherapy may allow performance of more breast-conserving procedures by decreasing the size of the tumor. In addition, the response to neoadjuvant chemotherapy is predictive of long-term disease-free and overall survival. Cancers with the highest response rate to neoadjuvant chemotherapy are those that are either HER2 positive or triple-negative tumors (tumors that are negative for estrogen receptor, progesterone receptor, and HER2 amplification). Patients with these types of cancer can be offered neoadjuvant chemotherapy even if decreasing the tumor size in order to perform breast-conserving surgery is not needed. After neoadjuvant chemotherapy, pathologic complete response, defined as the absence of any residual invasive cancer in the breast or lymph nodes, occurs in up to 60% of patients with HER2-positive cancers and up to 40% of those with triple-negative cancers and correlates with an excellent long-term disease-free survival.

The regimens used for neoadjuvant chemotherapy are generally the same as those used for postoperative adjuvant chemotherapy. Patients are closely monitored with breast exams during neoadjuvant chemotherapy to make sure they are responding. Unless a patient has tumor progression or is on a clinical trial assessing the response of a new regimen, all of the chemotherapy is usually completed before surgery. A patient with a HER2-positive cancer would receive trastuzumab during the nonanthracycline part of adjuvant chemotherapy, receiving 1 year of trastuzumab in total. Trastuzumab-containing regimens without anthracyclines are an option, particularly for women with a higher risk of cardiomyopathy because of older age or pre-existing hypertension. Pertuzumab is a newly approved anti-HER2 monoclonal antibody that may be used with trastuzumab and chemotherapy for neoadjuvant treatment of HER2-amplified breast cancers that measure 2 cm or more and/or are sentinel lymph node positive. The NeoSphere study demonstrated improved pathologic complete response rates (46% vs 29%) when pertuzumab was added to trastuzumab and docetaxel for HER2-amplified breast cancers with these higher risk features.

Immediate mastectomy is not required for this patient, who desires breast conservation and is likely to achieve this goal with neoadjuvant chemotherapy.

Neoadjuvant antiestrogen therapy (for example, with anastrozole) is an option for postmenopausal women with large or locally advanced breast cancers that are hormone receptor positive, particularly patients who are not good candidates for adjuvant chemotherapy because of advanced age or medical comorbidities. However, this therapy is not effective in patients with estrogen receptor–negative cancers.

As this patient does not have any worrisome symptoms or signs suggestive of systemic metastases, she does not need CT or bone scans for staging. Current American Society of Clinical Oncology (ASCO) guidelines recommend against performing PET, CT, or radionuclide bone scans in patients with stages 0 to II breast cancer in the absence of findings that would suggest metastatic disease.