Breast conservation surgery (BCS) is a
standard treatment for early-stage breast cancer, and includes a complete
removal of the tumor with a margin of tumor-free breast tissue. If margins of
the resected tissue are involved at final surgical pathology, patients undergo
additional surgery. Although MR imaging is the most sensitive modality for
breast cancer, the effect of preoperative MR imaging on the improvement of surgical
outcomes is controversial. There are only a few studies
evaluating association between preoperative MR imaging features and positive
resection margins (RMs) in patients with invasive breast cancer.
Breast conservation surgery (BCS) is a standard treatment for early-stage breast cancer, and includes a complete removal of the tumor with a margin of tumor-free breast tissue. If margins of the resected tissue are involved at final surgical pathology, patients undergo additional surgery. Although MR imaging is the most sensitive modality for breast cancer, the effect of preoperative MR imaging on the improvement of surgical outcomes is controversial[1-3]. There are only a few studies evaluating association between preoperative MR imaging features and positive resection margins (RMs) in patients with invasive breast cancer[4].
This retrospective study was approved by our institutional review board, and the requirement for informed consent was waived. A total of 636 women with invasive breast cancer who underwent preoperative MR imaging and surgery between January 2008 and December 2010 were selected. Patients who underwent neoadjuvant chemotherapy (n = 100), who underwent excisional biopsy (n = 52), or who had a personal history of breast cancer (n = 33) were excluded. Additionally, patients with unavailable surgical pathology reports (n = 11) and patients with occult primary breast cancer (n = 6) or bilateral breast cancer (n = 4) were excluded. Of the 430 patients, 254 (59.1%) underwent BCS as a primary procedure. Therefore, 254 patients with 254 cancers constituted our study population. The MR images were reviewed for descriptions of background parenchymal enhancement (BPE) level, fibroglandular tissue (FGT) amount, and multifocal or multicentric disease with no new interpretations made. Tumor size at MR imaging was determined on the basis of largest dimension provided. Mammographic findings were also reviewed. Data collected included patient age, mode of detection, biopsy method, biopsy pathology, pathologic tumor size (invasive component), histologic tumor type, histologic grade, axillary lymph node involvement, and breast cancer molecular subtype. A positive RM was defined as the presence of invasive cancer or ductal carcinoma in situ (DCIS) within 1 mm of the surgical RM[5].
Of the 254 patients, 80 (31.5%) had positive RMs and 174 (68.5%) had negative RMs. The mean age was significantly lower in patients with positive RMs than those with negative RMs (49.0 years ± 10.3 vs 52.2 years ± 10.9; P = .02). Stereotactic biopsy (22.5% [18 of 80] vs 10.3% [18 of 174]; P = .01) and the presence of DCIS on biopsy (75.0% [60 of 80] vs 48.9% [85 of 174]; P < .001) were reported significantly more frequently in patients with positive RMs. Invasive ductal and lobular histologic types were significantly more frequently reported in patients with positive RMs (30.0% [24 of 80] vs 9.8% [17 of 174]; P < .001). There was no significant difference between patients with positive or negative RMs in the proportion of histologic grade (P = .68), axillary lymph node involvement (P = .67), or breast cancer molecular subtype (P = .20). The mean pathologic tumor size was not significantly different between patients with positive RMs and those with negative RMs (1.3 cm ± 9.2 vs 1.3 cm ± 0.8; P = .83). However, the mean tumor size measured by MR imaging was larger in patient with positive RMs than those with negative RMs (2.4 cm ± 1.6 vs 1.7 cm ± 1.0; P = .001). MR imaging features associated with positive RMs included lesion type (P < .001) and multifocal or multicentric disease (P < .001). Patients with positive RMs were more likely than those with negative RMs to have non-mass enhancement (45.0% [36 of 80] vs 16.5% [27 of 174]) and multifocal or multicentric disease (23.7% [19 of 80] vs 7.9% [12 of 174]). There was no significant difference between patients with positive or negative RMs in the distribution of BPE level (P = .08) and FGT amount (P = .24). In terms of mammographic findings, calcifications, asymmetry, or architectural distortion were more frequently observed in patients with positive RMs (P = .008).
Non-mass enhancement or multifocal/multicentric disease on preoperative breast MR imaging and the presence of DCIS on biopsy were significantly associated with positive RMs in patients with invasive breast cancer. These MR imaging features can be helpful to reduce the reoperation rate in patients eligible for BCS.
[1] Turnbull L, Brown S, Harvey I, et al. Comparative effectiveness of MRI in breast cancer (COMICE) trial: a randomized controlled trial. Lancet 2010;375(9714):563-571.
[2] Mann RM, Loo CE, Wobbes T, et al. The impact of preoperative breast MR on the re-excision rate in invasive lobular carcinoma. Breast Cancer Res Treat. 2010;119(2):415-422.
[3] Obdeijn IM, Tilanus-Linthorst MM, Spronk S, et al. Preoperative breast MRI can reduce the rate of tumor-positive resection margins and reoperations in patients undergoing breast-conserving surgery. AJR Am J Roentgenol. 2013;200(2):304-310.
[4] Kim OH, Kim SJ, Lee JS. Enhancing patterns of breast cancer on preoperative dynamic contrast-enhanced magnetic resonance imaging and resection margin in breast conserving therapy. Breast Dis. 2016;36(1):27-35.
[5] Shin HC, Han W, Moon HG, et al. Nomogram for predicting positive resection margins after breast-conserving surgery. Breast Cancer Res Treat. 2012;134(3):1115-1123.