Tumor-to-breast volume ratio as measured on MRI: a possible predictor of breast-conserving surgery versus mastectomy.

BACKGROUND The surgical approach to breast cancer changed dramatically in the past 20 years. The surgical objective today is to remove the tumor, ensuring negative margins and good cosmetic results, and preserving the breast when possible. Magnetic resonance imaging of the breast has become an essential imaging tool prior to surgery, diagnosing additional tumors and assessing tumor extent. Tumor-to-breast volume ratio, an important predictor of breast conservation, can be measured with MRI and may change the surgical decision. OBJECTIVES To measure the tumor-to-breast volume ratio using MRI in order to assess whether there is a correlation between this ratio and the type of surgery selected (breast-conserving or mastectomy). METHODS The volumes of the tumor and the breast and the tumor-to-breast volume ratio were retrospectively calculated using preoperative breast MRI in 76 patients who underwent breast-conserving surgery or mastectomy. RESULTS Breast-conserving surgery (lumpectomy) was performed in 64 patients and mastectomy in 12. The average tumor-to-breast volume ratio was 0.06 (6%) in the lumpectomy group and 0.30 (30%) in the mastectomy group (P < 0.0001). CONCLUSION The tumor-to-breast volume ratio correlated with the type of surgery. As measured on MRI, this ratio is an accurate means of determining the type of surgery best suited for a given patient. It is recommended that MRI-determined tumor-to-breast volume ratio become part of the surgical planning protocol for patients diagnosed with breast cancer.