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Background:Neoadjuvant chemotherapy (NACT) is widely used as an efficient breast cancer treatment. Ideally, a pathological complete response (pCR) can be achieved. Up to date, there is no reliable way of predicting a pCR. For the first time, we explore the ability of minimal invasive biopsy (MIB) techniques to diagnose pCR in patients with clinical complete response (cCR) to NACT in this study. This question is of high clinical relevance because a reliable pCR prediction could have direct implications for clinical practice.Methods:In all, 164 patients were included in this review-board approved, multicenter pooled analysis of prospectively assembled data. Core-cut (CC)-MIB or vacuum-assisted (VAB)-MIB were performed after NACT and before surgery. Negative predictive values (NPV) and false-negative rates (FNR) to predict a pCR in surgical specimen (diagnose pCR through MIB) were the main outcome measures.Results:Pathological complete response in surgical specimen was diagnosed in 93 (56.7%) cases of the whole cohort. The NPV of the MIB diagnosis of pCR was 71.3% (95% CI: (63.3% 79.3%)). The FNR was 49.3% (95% CI: (40.4% 58.2%)). Existence of a clip marker tended to improve the NPV (odds ratio 1.98; 95% CI: (0.81; 4.85)). None of the mammographically guided VABs (n=16) was false-negative (FNR 0%, NPV 100%).Conclusions:Overall accuracy of MIB diagnosis of pCR was insufficient to suggest changing clinical practice. However, subgroup analyses (mammographically guided VABs) suggest a potential capacity of MIB techniques to precisely diagnose pCR after NACT. Representativity of MIB could be a crucial factor to be focused on in further analyses.

Neither MRI nor MGR or US can diagnose a pCR (ypT0) with sufficient accuracy to replace pathologic diagnosis of the surgical excision specimen.

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Objective: We evaluated the ability of minimally invasive, image-guided vacuum-assisted biopsy (VAB) to reliably diagnose a pathologic complete response in the breast (pCR-B). Summary Background Data: Neoadjuvant systemic treatment (NST) elicits a pathologic complete response in up to 80% of women with breast cancer. In such cases, breast surgery, the gold standard for confirming pCR-B, may be considered overtreatment. Methods: This multicenter, prospective trial enrolled 452 women presenting with initial stage 1-3 breast cancer of all biological subtypes. Fifty-four women dropped out; 398 were included in the full analysis. All participants had an imaging-confirmed partial or complete response to NST and underwent studyspecific image-guided VAB before guideline-adherent breast surgery. The primary endpoint was the false-negative rate (FNR) of VAB-confirmed pCR-B.Results: Image-guided VAB alone did not detect surgically confirmed residual tumor in 37 of 208 women [FNR, 17.8%; 95% confidence interval (CI), 12.8-23.7%]. Of these 37 women, 12 (32.4%) had residual DCIS only, 20 (54.1%) had minimal residual tumor (<5 mm), and 19 of 25 (76.0%) exhibited invasive cancer cellularity of 10%. In 19 of the 37 cases (51.4%), the false-negative result was potentially avoidable. Exploratory analysis showed that performing VAB with the largest needle by volume (7-gauge) resulted in no false-negative results and that combining imaging and imageguided VAB into a single diagnostic test lowered the FNR to 6.2% (95% CI, 3.4%-10.5%). Conclusions: Image-guided VAB missed residual disease more often than expected. Refinements in procedure and patient selection seem possible and necessary before omitting breast surgery.