Identifying ductal carcinoma in situ cases not requiring surgery to exclude postoperative upgrade to invasive ductal carcinoma

Background Prospective cohort studies are being conducted worldwide to identify a low-grade group of ductal carcinoma in situ (DCIS) that does not require surgery. However, to do this, it is necessary to predict which cases, diagnosed with preoperative DCIS, will be upgraded to invasive ductal carcinoma (IDC) after surgery. Methods In this study, we evaluated the frequency of IDC upgrades in patients who were preoperatively diagnosed with DCIS at Showa University using the criteria of ongoing clinical trials. We divided our cases into those that could be enrolled in the ongoing trial and those that could not. Moreover, we evaluated whether CNB, which is allowed only in Japanese clinical trials, is related to the IDC mixture. Results There were 211 (52.1%) cases that matched the criteria of the U.K. and Netherlands trials, of which 62 (29.4%) were upgraded to IDC. A total of 113 (27.9%) cases met the criteria for clinical trials in Japan and the U.S., 25 (22.1%) of which were upgraded to IDC and 47 (34.6%) which matched when considering biopsy methods. The number of cases upgraded to IDC decreased to four (8.5%). Conclusions This study demonstrated that there were a certain number of mixed IDC. We will pay attention to the results of ongoing clinical trials regarding how the presence of this mixed IDC affects the prognosis in non-surgery cases. Careful follow-up is recommended for non-surgical treatment.