Recurrence Patterns and Overtreatment in Pure DCIS: A Retrospective Clinical and Radiological Follow-Up Study

Background/Objectives: The clinical management of ductal carcinoma in situ (DCIS) remains controversial due to its heterogeneous biological behavior and uncertain risk of progression. Standard treatment often includes surgery and radiotherapy, although the actual recurrence risk varies considerably among patients. This study aimed to evaluate recurrence patterns and associated clinicopathological factors in a large single-center cohort of patients with pure DCIS. Methods: We retrospectively analyzed 403 patients with histologically confirmed pure DCIS treated with breast-conserving surgery or mastectomy between 2016 and 2023. Clinical, imaging, pathological, and treatment-related variables were assessed. Descriptive and exploratory comparative analyses were performed between patients with and without ipsilateral recurrence. Results: A total of 417 lesions were analyzed, with 21 ipsilateral recurrences (5%) observed during follow-up. Among recurrent cases, 57% were non-invasive recurrent DCIS and 38% were invasive carcinomas. Most recurrences occurred in patients treated with breast-conserving surgery, and 52% of recurrent patients had not received adjuvant radiotherapy. All recurrent cases were estrogen receptor-positive at initial diagnosis, whereas none had received endocrine therapy. No clear association between recurrence patterns and tumor grade or tumor size emerged in this exploratory analysis. No distant metastases or disease-related deaths were observed during follow-up. Conclusions: Recurrence after treatment for pure DCIS was relatively uncommon and frequently non-invasive. Traditional clinicopathological variables alone appeared insufficient to consistently identify recurrence patterns in this cohort. These findings support the need for more individualized risk stratification approaches integrating clinical, imaging, and molecular factors in order to reduce potential overtreatment in selected patients with DCIS.