Abstract P1-01-03: Value of breast MRI for preoperative axillary assessment of breast cancer patients
Authors: Dupont Sean C , Boughey Judy C , Hoskin Tanya L , Glazebrook Katrina N , Hieken Tina J 
Published: May 2015

Background: Many newly diagnosed breast cancer patients undergo preoperative breast MRI which includes visualization of some degree of the axilla. The impact of patient characteristics and tumor biology on the fidelity of MRI imaging of the axilla in these cases is not well-studied. We sought to examine the correlation between nodal findings on breast MRI and pathologic nodal status in newly diagnosed breast cancer patients.

Methods: With IRB approval, we identified 1868 consecutive breasts with invasive cancer in 1803 patients undergoing primary operation with axillary surgery from 1/2010-7/2013. Patients undergoing neoadjuvant chemotherapy (348) were excluded leaving 1510 breasts with cancer in 1455 patients. Preoperative MRI was performed in 763 patients (52%). We evaluated patient, imaging and pathology data.

Results: Patients evaluated with MRI were median age 57 years. The majority of tumors were T1 (63%) and T2 (28%). MRI identified suspicious axillary nodes in 240 cases (31%), of which 123 (51%) were node positive at operation. Suspicious axillary findings on MRI predicted both nodal status and pN stage at operation (both p&lt;0.0001). The sensitivity, specificity, accuracy, positive (PPV) and negative predictive value (NPV) of MRI for nodal disease across tumor types is shown.

 Pathologic Node PositiveSensitivity (95% CI)Specificity (95% CI)NPV (95% CI)PPV (95% CI)Accuracy (95% CI)All Cases (n=763)234 (31%)52.6 (46-59.1)77.9 (74.1-81.3)78.8 (75-82.1)51.3 (44.8-57.7)70.1 (66.7-73.3)Approximated Biologic Subtype (missing=24)ER+/HER2- (n=609)194 (32%)51.0 (43.8-58.2)80.0 (75.8-83.7)77.8 (73.4-81.5)54.4 (46.9-61.7)70.8 (67-74.3)HER2+ (n=69)20 (29%)65.0 (40.9-83.7)71.4 (56.5-83)83.3 (68-92.5)48.1 (29.2-67.6)69.6 (57.2-79.8)ER-/HER2- (n=61)17 (28%)58.8 (33.5-80.6)75.0 (59.4-86.3)82.5 (66.6-92.1)47.6 (26.4-70)70.5 (57.3-81.1)p value0.740.430.330.560.730.98Tumor Grade (missing=5)1 (n=259)58 (22%)32.8 (21.4-46.5)79.6 (73.2-84.8)80.4 (74.1-85.5)31.7 (20.6-45.1)69.1 (63.0-74.6)2 (n=351)124 (35%)55.6 (46.5-64.5)79.7 (73.8-84.6)76.7 (70.7-81.8)60.0 (50.4-68.9)71.2 (66.1-75.9)3 (n=148)51 (34%)66.7 (52.0-79.0)70.1 (59.8-78.8)80.0 (69.6-87.6)54.0 (41.0-66.4)68.9 (60.7-76.1)p value0.0010.00030.110.720.020.93

Diagnostic performance did not vary significantly based on patient body mass index (BMI) or approximated biologic subtype, but specificity was better for patients &gt;age 50 (p=0.007) and sensitivity and PPV both were worse for grade 1 vs grade 2/3 tumors. Node positivity rate at operation was 48% (51/106) for patients with a solitary abnormal node on MRI and 54% (72/134) when &gt;1 suspicious node was seen (p=0.39). However, multiple vs solitary MRI suspicious nodes correlated with ≥3 positive nodes at operation (40 [30%] vs 19 [18%], p=0.03) and pN2/pN3 disease (29 [22%] vs 12 [11%], p=0.03).

Conclusion: Axillary lymph node findings on MRI for breast cancer predict nodal status and disease volume in invasive breast cancer patients. Tumor biologic subtype did not affect performance characteristics of preoperative MRI, but tumor grade did influence the sensitivity and PPV of MRI. When MRI is performed in the evaluation of newly diagnosed breast cancer, axillary findings inform pathologic nodal stage at operation regardless of tumor subtype.

Citation Format: Sean C Dupont, Judy C Boughey, Tanya L Hoskin, Katrina N Glazebrook, Tina J Hieken. Value of breast MRI for preoperative axillary assessment of breast cancer patients [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P1-01-03.