Dr. Hunt is Professor of Surgery, Department of Surgical Oncology Chief, at MD Anderson Cancer Center Surgical Breast Section, and Chair Breast Committee American College of Surgeons Oncology Group.
Characteristics of both the tumor and the patient may help determine who would benefit from prophylactic contralateral mastectomy, researchers said.
Factors predictive of contralateral malignancy included five-year Gail risk of 1.67% or higher and an ipsilateral tumor with moderate- to-high-risk pathology, multicentric location, or invasive lobular histology, Kelly K. Hunt, M.D., of the University of Texas M.D. Anderson Cancer Center, and colleagues reported in the March 1 issue of Cancer.
Using these factors to define the risk when counseling patients may help to reduce the rate of contralateral prophylactic mastectomy, especially since patients have less extreme options for risk reduction, the researchers said.
Other strategies to reduce contralateral breast cancer risk include systemic chemotherapy and endocrine therapy and the use of MRI along with mammography to improve contralateral breast cancer detection, they noted.
Patients most often choose contralateral prophylactic mastectomy on the advice of their physician or because of their own fear of developing another breast cancer, desire for cosmetic symmetry, family history, or fibrocystic breast disease that makes surveillance more challenging.
However, "most patients will not experience any survival benefit," the researchers noted, "because the risk of systemic metastases from their index cancer often exceeds the risk of developing a contralateral breast cancer."
To determine what factors might determine which patients would benefit, the researchers analyzed findings for 542 unilateral breast cancer patients who underwent prophylactic contralateral mastectomy at M.D. Anderson over a seven-year period.
These patients were found to have a low risk of occult cancer in the contralateral breast (4.6%).
By comparison, the incidence of contralateral breast cancer was 0.56% per year (2.4% at 50.2 months) among a tumor stage-, age-, and race-matched control group of 1,574 breast cancer patients who did not chose prophylactic contralateral mastectomy.
This finding suggested that contralateral prophylactic mastectomy "led to early detection and resection of already existing contralateral breast cancers more than prevention of expected contralateral cancers," the researchers noted.
In the overall multivariate analysis, the independent factors predictive of a malignancy in the contralateral breast were:
- An ipsilateral invasive lobular histology (odds ratio 3.4, P=0.01).
- An ipsilateral multicentric tumor (OR 3.1, P=0.004).
- A high five-year Gail risk (1.67% or greater, OR 3.5, P=0.005).
When the findings were stratified by whether patients received neoadjuvant chemotherapy, the independent predictive factors among those who didn't receive chemotherapy were an ipsilateral multicentric tumor (OR 3.7, P=0.03) and high five-year Gail risk (OR 4.6, P<0.0001).
But only ipsilateral invasive lobular histology (OR 21.3, P=0.0009) was predictive among those who got chemotherapy.
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