The role of radiotherapy (RT) in the treatment of Adenoid Cystic Carcinoma of the Breast: case report of RT retreatment and literature review

Aim: This study reviews the recent literature on the role of definitive radiotherapy (RT) in the management of adenoid cystic carcinoma of the breast (ACCB) and presents comprehensive data on clinical outcomes. A case report of radiotherapy retreatment in ACCB is reported for first time in literature. Methods: The authors performed a literature review using PubMed (1981-2019) to identify all studies that match with keywords. Inclusion criteria were articles reporting patients underwent radiotherapy after ACCB diagnosis with follow up reporting. Data analyzed were number of pts, age, study design, multimodality treatment management with radiotherapy schedule, stage of disease, pathological risk factors, local relapse free survival (LFRS), metastases free survival (MFS) and overall survival (OS). Results: Of the 60 identified studies, 15 met the inclusion criteria. All studies had a retrospective design. Overall, 967 patients (median, 64; range, 1-478) were included. A high heterogeneity was found across studies in terms of pathological features available, local approach in multimodality management, adjuvant RT administration, and reported outcomes. Mean LRFS reported by case reports was 24 months (range 20-48). Mean DFS reported by case series and retrospective series was 87.9% (range 69-100%). Mean OS reported in case reports was 30 months (range 12-84). Mean 5-years OS reported in retrospective series was 89.7%. Mean 10-years OS reported in retrospective series was 78.7%. In some retrospective series radiotherapy was found significantly related to local control (p=0.03) and with an absolute survival benefit of 9% at 5 year and of 21% at 10 years (p=0.005). Conclusion and implications for practice: To our knowledge this is the first report on radiotherapy retreatment in ACCB local relapse. This study also reviews the recent literature on the role of adjuvant RT in the management of ACCB and presents comprehensive data on long-term clinical outcome. Some significant results about RT are improvement in local control and survival benefit also since at 10 years in some series. Further studies are needed to confirm these results.