The effect of boost radiotherapy on local control in ductal carcinoma in-situ of the breast: Retrospective single-center experience with literature review

Purpose: We aimed to investigate factors related to local recurrence and especially the effects of additional radiotherapy (RT) boost after whole breast radiation therapy (WBRT) on local recurrence in ductal carcinoma in situ (DCIS) patients undergoing breast-conserving surgery (BCS). Methods: In this retrospective analysis, 197 patients treated for DCIS between 1998-2018 were evaluated. Patients with microinvasion, intracystic in situ cancer, undergoing mastectomy, less than 12 months of follow-up, and missing information were excluded. Results: The median age was 50 years (28-78). The median follow-up time was 97 months (12-257). Local recurrence occurred in eight patients (4%), six of them were invasive and two were DCIS. Systemic metastasis was present in a patient who recurred as invasive cancer. Contralateral breast cancer developed in nine patients (4.5%). Boost radiation was given to patients 143 (72.6%). Local recurrence developed in two patients (3.7%) without boost and six patients (4.2%) with boost; there was no significant difference in local recurrence free survival between patients with and without boost radiation (p=0.94). The factors affecting significantly local recurrence were age, tumor diameter, and surgical margin width (≤ 2 mm) in univariate analysis, but only tumor diameter and surgical margin width (≤ 2 mm) in multivariate analysis. Conclusion: Surgical margin width and tumor diameter were independently associated with local recurrence. In contrast, patient age, RT boost, hormonotherapy use, and poor histological features were not significantly associated with local recurrence.