Breast conservation for ductal carcinoma in situ: Results at an Australian institution with evidence to recommend prospective assessment of the utility of a lumpectomy boost

Aim: We reviewed outcomes for ductal carcinoma in situ (DCIS) of the breast at our institution to assess risk factors for ipsilateral breast tumour recurrence (IBTR) after breast conservation (BCT). Methods: Records were reviewed of all patients who presented with biopsy‐confirmed DCIS of the breast prior to 1 January 2004. Variables analyzed included patient age, tumour size, grade, resection margins, comedonecrosis, surgery, tamoxifen, whole breast radiotherapy dose and addition of a boost. We also attempted to validate the University of Southern California/Van Nuys prognostic index (USC/VNPI). Results: One hundred and thirty patients had DCIS: four were excluded from analysis and another 10 had mastectomies. A total of 116 patients had BCT and this group comprised the study population. Median follow‐up was 7.7 years (1.6–12.4) and median age was 58 years. Five‐ and 10‐year overall survivals were 98% (93.5–99.6 95% CI) and 89% (74–95 95% CI). Five‐ and 10‐year breast failure‐free survivals were 96% (90–98 95% CI) and 93% (85–97 95% CI). Young age was the only significant factor associated with IBTR (P = 0.018). Patients with a high USC/VNPI score were also significant for increased IBTR (P = 0.04), but this effect disappeared when age was omitted from the index. There was a trend towards an increased risk of IBTR with a lower whole breast dose of less than 50 Gy (P = 0.18). A boost was not associated with reduced IBTR. The 10‐year IBTR for patients under 55 who received adjuvant radiotherapy to a whole breast dose of <50 Gy but no tamoxifen was 25%. Conclusion: Overall BCT local control and survival outcomes are excellent. There is a suggestion that younger patients should be treated with a whole breast dose equivalent to 50 Gy in 25 daily fractions regardless of a boost. However, this requires confirmation in a randomized phase III trial and therefore the currently active Trans‐Tasman Radiation Oncology Group randomized controlled trial 07.01 should be supported by the breast cancer treating community.