Predicting the response to Neoadjuvant Chemotherapy. Can the addition of tomosynthesis improve the accuracy of CESM? A comparison with breast MRI

Background Neoadjuvant chemotherapy (NACT) is used to downstage breast cancer prior to surgery. Image monitoring is essential to guide treatment and to assess in vivo chemosensitivity. Breast MRI is considered the gold-standard imaging technique; however, it is contraindicated or poorly tolerated in some patients and may be hard to access. Evidence suggests contrast enhanced spectral mammography (CESM) may approach the accuracy of MRI. This novel pilot study investigates whether the addition of digital breast tomosynthesis (DBT) to CESM increases the accuracy of response prediction. Results Sixteen cancers in fourteen patients were imaged with CESM+DBT and MRI following completion of NACT. Ten cancers demonstrated pathological complete response (pCR) defined as absence of residual invasive disease. Greatest accuracy for predicting pCR was with CESM contrast-enhancement only (accuracy 81.3%, sensitivity 100%, specificity 57.1%), followed by MRI (accuracy 62.5%, sensitivity 44.4%, specificity 85.7%). Concordance with invasive tumour size was greater for CESM than MRI, concordance-coefficients 0.70 vs 0.66 respectively. MRI demonstrated greatest concordance with whole tumour size followed by CESM contrast-enhancement plus microcalcification, concordance-coefficients 0.86 vs 0.69. The addition of DBT did not improve accuracy for prediction of pCR or residual disease size. Whereas CESM+DBT tended to underestimate size of residual disease, MRI tended to overestimate but no significant differences were seen (p>0.05). Conclusions CESM contrast-enhancement plus microcalcification is similar to MRI for predicting residual disease post-NACT. Size of enhancement alone demonstrates best concordance with invasive disease. Inclusion of residual microcalcification improves concordance with DCIS. The addition of DBT to CESM does not improve accuracy. Highlights ### Competing Interest Statement The authors have declared no competing interest. ### Clinical Trial researchregistry5895 ### Funding Statement TENOVUS Scotland British Society of Breast Radiologists ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: Research ethics committee of the West of Scotland gave ethical approval for this work I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable. Yes All data produced in the present study are available upon reasonable request to the authors * CESM : Contrast-enhanced spectral mammography DCIS : Ductal carcinoma in situ DBT : Digital breast tomosynthesis FEC-T : Fluorouracil (5FU), epirubicin, cyclophosphamide and docetaxel FFDM : Full field digital mammography IDC : Invasive ductal carcinoma ILC : Invasive lobular carcinoma ITS : Invasive tumour size MRI : Magnetic resonance imaging NACT : Neoadjuvant chemotherapy pCR : Pathological complete response WTS : Whole tumour size