A 52-year-old woman comes to the office for follow-up a week after undergoing right breast partial mastectomy and right axillary sentinel lymph node biopsy. She was recently diagnosed with invasive ductal carcinoma after mammography detected a hyperdense lesion in the right breast. Vital signs are normal. The right breast and axilla have mild, but appropriate, swelling; incisions are clean and intact, without erythema. Surgical pathology reveals completely excised invasive ductal carcinoma; ductal carcinoma in situ is present at the specimen's lateral margin. The tumor is estrogen receptor–, progesterone receptor–, and HER2-negative. The axillary sentinel lymph node is negative for metastasis. Which of the following is the best next step in management of this patient's breast cancer?
Breast conserving therapy (BCT) is an alternative to mastectomy for many patients with early stage, unifocal breast cancer. BCT typically begins with partial mastectomy (aka, lumpectomy) to excise all invasive and/or in situ cancer (eg, ductal carcinoma in situ), along with axillary sentinel lymph node biopsy. The specimen, consisting of the removed tumor and a border of surrounding tissue (ie, margins), is examined under the microscope. Surgical pathology then determines the next steps:
Partial mastectomy: positive margins (eg, ductal carcinoma in situ at the lateral margin in this patient) require reexcision of the involved margins. In contrast, negative margins indicate that local tumor resection from the breast is complete.
Sentinel lymph node biopsy: positive sentinel lymph nodes may warrant axillary lymph node dissection (typically performed for ≥3 positive nodes). In contrast, negative lymph nodes indicate that lymph node resection is complete.
Following surgical therapy, radiation therapy is performed to eradicate any remaining tumor deposits and reduce the risk of locoregional recurrence. It is initiated only after negative surgical margins are obtained because positive margins double the rate of local recurrence. Reexcision is required to achieve negative margins in up to 25% of patients treated with BCT, and multiple reexcision attempts may be performed before resorting to completion mastectomy.
(Choice A) Aromatase inhibitors (eg, anastrozole) reduce the peripheral conversion of androgens to estrogens, thereby decreasing plasma estrogen levels and potential estrogen stimulation of any residual hormone receptor–positive breast cancer. They would not be helpful in this patient with a hormone receptor–negative tumor.
(Choice B) Breast MRI is most often used when mammography and ultrasound are inconclusive in the workup of a breast mass and is sometimes used for screening patients at highest risk for breast cancer (eg, BRCA mutation). This patient has no such indication. In addition, MRI is unlikely to detect her residual disease, which may be microscopic.
(Choice C) This patient's surgical specimen has a positive margin; therefore, reexcision (rather than observation) should be performed to decrease the risk of future recurrence. Following BCT, mammography should be resumed at least annually.
(Choice E) Modified radical mastectomy includes mastectomy (removal of the entire breast and nipple areolar complex) and axillary lymph node dissection. Although this patient has residual disease and needs additional surgery, reexcision is a typical next step and is less morbid than mastectomy. In addition, lymph node dissection is not warranted in this patient with a negative axillary sentinel lymph node.
Educational objective:
Breast conserving therapy typically consists of partial mastectomy and axillary sentinel lymph node biopsy, followed by whole breast radiation therapy. Adequate surgical excision of the cancer requires negative margins.