title: Effect of breast cancer phenotype on diagnostic performance of MRI in the prediction to response to neoadjuvant treatment.
abstract: OBJECTIVE
  The estimation of response to neoadjuvant chemotherapy (NAC) is useful in the surgical decision in breast cancer. We addressed the diagnostic reliability of conventional MRI, of diffusion weighted imaging (DWI) and of a merged criterion coupling morphological MRI and DWI. Diagnostic performance was analysed separately in different tumor subtypes, including HER2+ (human epidermal growth factor receptor 2)/HR+ (hormone receptor) (hybrid phenotype).
  
  
  METHODS
  Two-hundred and twenty-five patients underwent MRI before and after NAC. The response to treatment was defined according to the RECIST classification and the evaluation of DWI with apparent diffusion coefficient (ADC). The complete pathological response - pCR was assessed (Mandard classification).
  
  
  RESULTS
  Tumor phenotypes were Luminal (63.6%), Triple Negative (16.4%), HER2+ (7.6%) or Hybrid (12.4%). After NAC, pCR was observed in 17.3% of cases. Average ADC was statistically higher after NAC (p<0.001) among patients showing pCR vs. those who had not pCR. The RECIST classification showed adequate performance in predicting the pCR in Triple Negative (area under the receiver operating characteristic curve, ROC AUC=0.9) and in the HER2+ subgroup (AUC=0.826). Lower performance was found in the Luminal and Hybrid subgroups (AUC 0.693 and 0.611, respectively), where the ADC criterion yielded an improved performance (AUC=0.787 and 0.722). The coupling of morphological and DWI criteria yielded maximally improved performance in the Luminal and Hybrid subgroups (AUC=0.797 and 0.761).
  
  
  CONCLUSIONS
  The diagnostic reliability of MRI in predicting the pCR to NAC depends on the tumor phenotype, particularly in the Luminal and Hybrid subgroups. In these cases, the coupling of morphological MRI evaluation and DWI assessment may facilitate the diagnosis.
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University, 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, Rome, Italy.
authors.forename: Paolo
authors.initials: P
authors.lastname: Belli
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University, Rome, Italy.
authors.forename: Marialuisa
authors.initials: M
authors.lastname: Di Matteo
authors.affiliation: Department of Surgery, Breast Unit, Catholic University, Rome, Italy.
authors.forename: Daniela
authors.initials: D
authors.lastname: Terribile
authors.affiliation: Department of Surgery, Breast Unit, Catholic University, Rome, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Franceschini
authors.affiliation: Department of Radiotherapy, Catholic University, Rome, Italy.
authors.forename: Luigia
authors.initials: L
authors.lastname: Nardone
authors.affiliation: Department of Pathology, Catholic University, Rome, Italy.
authors.forename: Gianluigi
authors.initials: G
authors.lastname: Petrone
authors.affiliation: Department of Bioimaging and Radiological Sciences, Catholic University, Rome, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Bonomo
mesh_terms: D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use; D001943:Breast Neoplasms / Q000188:drug therapy* / Q000473:pathology*; D017024:Chemotherapy, Adjuvant / Q000379:methods; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008875:Middle Aged; D020360:Neoadjuvant Therapy / Q000379:methods*; D010641:Phenotype; D011237:Predictive Value of Tests; D015203:Reproducibility of Results; D016896:Treatment Outcome
keywords: Breast cancer; Complete Pathological response; Diffusion weighted imaging; Neoadjuvant chemotherapy; RECIST classification; Tumor subtype