Positron emission tomography/computed tomography (PET/CT) as a biomarker of pathologic response to neoadjuvant chemotherapy in breast carcinoma.

Abstract

e21147 Background: Pathological complete response (pCR) after neoadjuvant chemotherapy (NAC) in breast carcinoma is prognostic. Predictive biomarkers for pCR include early response to NAC, estrogen receptor (ER) negativity, HER2 positivity, and high Ki67. We assessed whether absence of fluoro-deoxy glucose (FDG) uptake measured by standardized uptake value (SUV) after NAC would predict pCR. Methods: We identified 23 patients (pts) who had PET/CT scanning pre and post NAC. We examined breast cancer subtype, chemotherapy (CT) regimen, number of cycles of CT given, clinical and pathological staging data and changes in SUV in the breasts and lymph nodes pre and post NAC. pCR was defined as no residual cancer in the breast or axillary lymph nodes. Results: Median age at diagnosis was 46 years (IQR; 37 to 56). Median tumor size at diagnosis was 30mm (IQR; 25 to 43) and 19 pts (83%) had node positive breast cancer. Most tumors were ductal (n=22) with 1 lobular cancer. Preoperatively 95% received all CT. All HER2+ pts received Trastuzumab. Anthracycline/taxane based regimens were most frequently given in 22 cases, 1 received lapatinib/trastuzumab. Five tumors (21.7%) were ER+/HER2+; 14 (60.9%) ER+/HER2-; 2 (8.7%) ER-/HER2+ and 2 (8.7%) were ER-/HER2-. All tumors were high (n=9, 39.1%) or intermediate grade (n=14, 61%). SUV was significantly lower post NAC (p=0.035). We observed no SUV uptake in breast or lymph nodes in 15 cases (65.2%) post NAC, these corresponded to; ER+HER2+ 4/5 (80%); ER+HER2- 7/15 (46.7%); ER-HER2- 2/2(100%), ER-HER2+ 2/2(100%). Absent SUV uptake post NAC was associated with a pCR (breast and lymph nodes) in 5/15 (33%) of pts (ER+HER2+ n=1, ER+HER2- n=1, ER-HER2- n=2, ER-HER2+ n=1). Ten of 15 tumors (67%) had no SUV uptake in the breast post NAC and 7 (47%) were associated with a pCR. There was a trend toward increased odds of pCR with no SUV uptake post NAC (OR 2.76; 95% CI 0.85 to 8.94: P= 0.09). Overall rate of pCR was 21.7% (n=5). Conclusions: A non-statistically significant trend toward increased odds of pCR with no SUV uptake post NAC was observed. Larger subtype-specific breast cancer cohorts will be required to determine the value of PET/CT as a predictive biomarker for pCR.