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Purpose The aim of this study was to evaluate the role of apparent diffusion coefficient (ADC) and hence diffusion-weighted imaging in prediction of pathological complete response (pCR) to neoadjuvant chemotherapy (NACT) in locally advanced breast cancer (LABC) and its molecular subtypes. Methods In this tertiary hospital-based prospective study, 30 patients aged 30 to 65 years, having clinically/cytologically diagnosed LABC, were included. Magnetic resonance imaging (MRI) was done to obtain prechemotherapy ADC (ADC pre), postchemotherapy ADC (ADC post), change in ADC (ΔADC), and ΔADC% for each tumor and its subtype. Postsurgical pCR was used as the reference standard for determining tumor response. All four ADC parameters were compared between pCR and non-pCR groups. Results Of the 30 patients, 19 (63.3%) patients showed pCR, while 11 (36.7%) patients did not. The pCR group showed significantly lower mean ADC pre (p < 0.001) and higher mean ADC post (p < 0.05), ΔADC, and ΔADC% (p = 0.000) than non-pCR group. The best cutoff values to differentiate responders from nonresponders with receiver operating characteristic curve analysis of ADC pre , ADC post , and ΔADC% were 0.98 × 10 −3 mm 2 /s (68.4% sensitivity, 63.6% specificity), 1.31×10 −3 mm 2 /s (68.4% sensitivity, 63.6% specificity), and 25% (84.2% sensitivity, 90.9% specificity), respectively. Human epidermal growth factor receptor 2 (HER2)-enriched subtype showed significant difference in mean ADC pre (p = 0.045), while triple-negative subtype showed significant differences in mean ADC post (p = 0.032) and mean ΔADC (p = 0.019) between the two groups. Conclusion ADC pre , ADC post , and ΔADC can predict pCR to NACT in LABC. Among molecular subtypes, ADC pre was predictive only in HER2-enriched subtype, while ADC post and ΔADC were predictive only in triple-negative subtype. [ABSTRACT FROM AUTHOR]

Evaluation of expression of estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor 2 (HER2/neu) receptor was carried out on 80 breast cancer patients before and after neoadjuvant chemotherapy (NAC). No differences in expression were noted in 89% with reference to ER, 95% with reference to PR, and 91% with reference to HER2/neu status. A change in receptor status from positive to negative was noted in 12% for ER, 5% for PR, and 21% for HER2/neu after NAC. A negative to positive shift was noted in 11% for ER, 4% for PR, and 4% for HER2/neu after NAC. The possible reasons ascribed for change in receptor status after NAC are as follows: (1) Selection of chemoresistant clones with different receptor expression after NAC. (2) Tumor heterogeneity with variable receptor expression in different areas. (3) Ovarian suppression during NAC leading to alteration in receptor expression. (4) Technical considerations such as staining techniques and intra-observer and inter-observer differences in IHC slide interpretation before and after NAC. [ABSTRACT FROM AUTHOR]