Breast MRI in the evaluation of eligibility for accelerated partial breast irradiation

Eligibility for accelerated partial breast irradiation is generally determined by physical examination in conjunction with conventional imaging techniques such as mammography and breast sonography. MRI is recognized as a significant imaging tool in diagnosing breast cancer and has shown the ability to identify mammographically occult carcinoma. Our purpose was to retrospectively assess preoperative breast MRI examinations in women with early-stage breast cancer who were theoretically eligible for accelerated partial breast irradiation and to explore the use of MRI in selecting patients for this treatment.

Seventy-nine patients with core needle biopsy-proven breast cancer, who were eligible candidates for breast-conserving surgery and accelerated partial breast irradiation, underwent bilateral breast MRI examinations. At review, the presence and location of occult tumor sites (detected on MRI only) were documented and subsequently correlated with pathology findings.

From 79 patients, a total of 126 suspicious areas, including the index tumors, were detected by MRI. Additional sites of cancer other than the index tumor were observed in 30 patients (38%). Of these, eight (10%) had an additional cancer in a different quadrant from the index tumor.

The treatment effect of whole-breast irradiation on microscopic tumor cells and on additional occult foci in other quadrants of the breast is lost with partial breast irradiation. Our results suggest that MRI before accelerated partial breast irradiation may be of benefit to patients to ensure they do not have multifocal or multicentric disease, remote from the lumpectomy bed.