Diagnosis of complete response to neoadjuvant chemotherapy using diagnostic imaging in primary breast cancer patients

Advances in the therapeutic agents used for neoadjuvant chemotherapy (NAC) have recently achieved higher response rates and induced a greater number of pathologic complete responses (pCR) than ever before. The aim of this study is the diagnosis of pCR after NAC by diagnostic imaging of clinical complete response (cCR) patients. This study included 35 breast cancer patients who demonstrated cCR after receiving NAC with a combination of anthracycline and taxane from May 1998 to August 2003. Surgical treatment included breast-conserving therapy followed by radiotherapy or mastectomy. The identity of post-NAC lesions as either a complete response (CR) or partial response (PR) were made by mammography, ultrasonography, and contrast-enhanced computed tomography (CT). Among the 35 patients, 11 achieved pCR, including the disappearance of both invasive and intraductal components. Of the patients achieving pCR, eight were defined as CR and three were determined to be PR by CT. There was a significant relationship between the pCR and the determination of CR by CT. The determination of CR by ultrasonography was indicative of the disappearance of pathologic invasive components. While mammography appeared to reflect the observed histologic results, we did not observe any statistical differences. A subset of cases exhibited discrepancies between the imaging and pathologic results, likely due to the replacement of destroyed tumor cells by fibrosis and granulomatous tissue. The evaluation of CR by CT was significantly indicative of pCR. The positive predictive value, however, was not large enough to avoid surgical treatment. Further studies will be needed to establish a diagnosis of pCR.