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Old 02-01-2011, 02:11 PM   #1
Hopeful
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MRI monitoring during neoadjuvant therapy dependent on bc type

Magnetic Resonance Imaging Response Monitoring of Breast Cancer During Neoadjuvant Chemotherapy: Relevance of Breast Cancer Subtype

J Clin Oncol. 2011 Jan 10;[Epub Ahead of Print], CE Loo, ME Straver, S Rodenhuis, SH Muller, J Wesseling, MJ Vrancken Peeters, KG Gilhuijs

This study looked at patient response to neoadjuvant chemotherapy as monitored by MRI; response can be interpreted only if the cancer subtype is known as MRI changes are predictive in triple-negative and HER2-positive subtypes only.

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This study looked at patient response to neoadjuvant chemotherapy as monitored by MRI; response can be interpreted only if the cancer subtype is known as MRI changes are predictive in triple-negative and HER2-positive subtypes only.

SUMMARY

OncologySTAT Editorial Team


Breast cancer is a heterogeneous disease. Subtypes differ in treatment outcome based, in part, on hormone receptor (estrogen receptor [ER]; progesterone receptor [PR]) and human epidermal growth factor receptor 2 (HER2) status. Subtypes may be classified as triple-negative (ER, PR, and HER2 negative), HER2-positive (ER and PR positive or negative), and ER-positive (HER2 negative, PR positive or negative). Chemotherapy response varies within these subtypes; therefore, monitoring may identify nonresponding tumors. Dynamic contrast-enhanced magnetic resonance imaging (MRI) differentiates between residual tumor and nonvascularized therapy-induced fibrosis, and may be used to identify residual tumor after completion of neoadjuvant chemotherapy. This study evaluated the differences among breast cancer subtypes on MRI markers for disease response to neoadjuvant chemotherapy.

Patients were offered neoadjuvant chemotherapy if they had pathologically proven invasive breast cancer > 3 cm and/or ≥ one tumor-positive lymph node. Patients were included who received two MRI examinations, one before and a second during neoadjuvant chemotherapy, and who underwent surgery after neoadjuvant chemotherapy. Excluded were patients with HER2-positive breast cancer who did not receive trastuzumab. Patients with HER2-negative tumors received six courses of cyclophosphamide and doxorubicin every 2 weeks; some patients received six courses of capecitabine and docetaxel or doxorubicin and docetaxel. Chemotherapy regimens were switched if no or little response was noted after three courses. Patients with HER2-positive tumors received trastuzumab plus paclitaxel and carboplatin (8-week course) followed by trastuzumab, paclitaxel, and carboplatin (two 8-week courses) or trastuzumab plus fluorouracil, epirubicin, and cyclophosphamide (4 courses). Patients underwent mastectomy or breast-conserving therapy following chemotherapy. MRI with gadolinium-containing contrast medium on a T1 sequence was performed using a 1.5-T or 3.0-T scanner before and during neoadjuvant chemotherapy. MRI interpretation was blinded.

A total of 188 patients were included. Most patients (55%) had ER-positive/HER2-negative tumors; the remaining patients had triple-negative (25%) or HER2-positive (20%) tumors. Residual tumor was found in 93%, 66%, and 60% of patients with ER-positive/HER2-negative, triple-negative, and HER2-positive tumors, respectively (p < .001).

Triple-negative tumors were more likely to be a unifocal mass on MRI at baseline (57%) than HER2-positive (18%) or ER-positive/HER2-negative tumors (33%; p = .001), while HER2-positive tumors were more likely to be multifocal on MRI at baseline (53%) than the triple-negative (32%) or ER-positive tumors (30%; p = .02). During neoadjuvant chemotherapy, triple-negative tumors regressed as a shrinking mass on MRI significantly more often than the other subtypes (p < .001). On multiple logistic regression analysis of residual disease on MRI, significant factors included breast cancer subtype, late enhancement during neoadjuvant chemotherapy, and pattern of reduction between baseline and neoadjuvant chemotherapy. These factors were significant for triple-negative (r = 0.605; p < .001) and HER2-positive tumors (r = 0.426; p < .01) but not for ER-positive/HER2-negative tumors (r = 0.074; p = .458). On multivariate analysis, no markers showed significant associations with residual disease or breast cancer response index (BRI) in the ER-positive/HER2-negative group. In the triple-negative and HER2-positive groups, the only significant factor on multivariate analysis was the change in largest tumor diameter at late enhancement between baseline MRI and MRI during neoadjuvant chemotherapy (area under the receiver operating characteristic curve, 0.76; p < .001).

The ability of MRI to identify response to neoadjuvant chemotherapy differed among subtypes; MRI changes were predictive of pathology outcome in the triple-negative and HER-2 positive groups, but not in the ER-positive/HER2-negative group.

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