ASO Visual Abstract: The Absence of Cancer in the Location of a Breast Tissue Marker After Neoadjuvant Chemotherapy May Predict Pathological Complete Response with High Accuracy—Results from a Phase II Trial

Background It is difficult to determine pathological complete response (pCR) before surgery in clinical complete response (cCR) cases by imaging alone. We designed a prospective study to evaluate whether a breast tissue marker placed in a tumor before neoadjuvant chemotherapy (NAC) can predict a pCR, possibly removing the need for surgery. Methods We recruited patients with primary invasive breast cancer assigned to undergo curative surgery and possible NAC. A breast marker (UltraClip ® ) was placed in the primary tumor before standard NAC. We evaluated the probability of no cancer in the marker but cancer in removed specimens from a cCR group. Results A total of 102 patients were enrolled. Patients were categorized by cancer stage and subtypes. Seventy-two patients (70.6%) received standard NAC; 23 (34.3%) attained cCR, of whom pCR was obtained in 12 (52.2%). The probability of no cancer in the marker’s location but cancer in the removed specimens was 4.3% (95% confidence interval, 0.1–21.9). The false-negative rate was 9.1% (1/11), and the negative predictive value was 92.3% (12/13). In only one case, no cancer was found in the marker’s location, but cancer cells were present in the removed specimen. Conclusions The absence of cancer in the location of a breast tissue marker after NAC predicted pCR with high accuracy. Therefore, the rebiopsy of a marker’s location might mean surgery is unnecessary.