title: Role of the Apparent Diffusion Coefficient in the Prediction of Response to Neoadjuvant Chemotherapy in Patients With Locally Advanced Breast Cancer.
abstract: BACKGROUND
  We evaluated the diagnostic performance of the baseline diffusion weighted imaging (DWI) and the apparent diffusion coefficient (ADC) in the prediction of a complete pathologic response (pCR) to neoadjuvant chemotherapy (NAC) in patients with breast cancer stratified according to the tumor phenotype.
  
  
  METHODS
  We retrospectively studied 225 patients with stage II, III, and IV breast cancer who had undergone contrast-enhanced magnetic resonance imaging (MRI) and DWI before and after NAC, followed by breast surgery.
  
  
  RESULTS
  The tumor phenotypes were luminal (n = 143; 63.6%), triple-negative (TN) (n = 37; 16.4%), human epidermal growth factor receptor 2 (HER2)-enriched (n = 17; 7.6%), and hybrid (hormone receptor-positive/HER2(+); n = 28; 12.4%). After NAC, a pCR was observed in 39 patients (17.3%). No statistically significant difference was observed in the mean ADC value between a pCR and no pCR in the general population (1.132 ± 0.191 × 10(-3) mm(2)/s vs. 1.092 ± 0.189 × 10(-3) mm(2)/s, respectively; P = .23). The optimal ADC cutoff value in the general population was 0.975 × 10(-3) mm(2)/s (receiver operating characteristic [ROC] area under the curve [AUC], 0.587 for the prediction of a pCR). After splitting the population into subgroups according to tumor phenotype, we observed a significant or nearly significant difference in the mean ADC value among the responders versus the nonresponders in the TN (P = .06) and HER2(+) subgroups (P = .05). No meaningful difference was seen in the luminal and hybrid subgroups (P = .59 and P = .53, respectively). In contrast, in the TN and HER2(+) subgroups (cutoff value, 0.995 × 10(-3) mm(2)/s and 0.971 × 10(-3) mm(2)/s, respectively), we observed adequate ROC AUCs (0.766 and 0.813, respectively).
  
  
  CONCLUSIONS
  The pretreatment ADC value is not capable of predicting the pCR in the overall population of patients with locally advanced breast cancer. Nonetheless, an ameliorated diagnostic performance was observed in specific phenotype subgroups (ie, TN and HER2(+) tumors).
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy. Electronic address: reagandus@alice.it.
authors.forename: Enida
authors.initials: E
authors.lastname: Bufi
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Belli
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Melania
authors.initials: M
authors.lastname: Costantini
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Cipriani
authors.affiliation: Department of Pathology, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Marialuisa
authors.initials: M
authors.lastname: Di Matteo
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Angelo
authors.initials: A
authors.lastname: Bonatesta
authors.affiliation: Department of Surgery, Breast Unit, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Franceschini
authors.affiliation: Department of Surgery, Breast Unit, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Terribile
authors.affiliation: Department of Pathology, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Antonino
authors.initials: A
authors.lastname: Mulé
authors.affiliation: Department of Radiotherapy, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Luigia
authors.initials: L
authors.lastname: Nardone
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University of Sacred Heart, "Agostino Gemelli" Hospital, Rome, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Bonomo
mesh_terms: D000328:Adult; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology* / Q000601:surgery; D017024:Chemotherapy, Adjuvant / Q000379:methods; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D006801:Humans; D008875:Middle Aged; D020360:Neoadjuvant Therapy / Q000379:methods*; D009362:Neoplasm Metastasis; D010641:Phenotype; D012189:Retrospective Studies; D016896:Treatment Outcome; D047368:Tumor Burden
chemical_list: D000970:Antineoplastic Agents
keywords: Breast cancer phenotypes; Diffusion weighted imaging; Magnetic resonance imaging; Response prediction