Current pattern of care in radiation therapy for DCIS in Australia and New Zealand - where are we heading?

Background

Ductal carcinoma in-situ (DCIS) is a non-obligate precursor breast lesion with variable tendency to become invasive malignancy. Multiple studies have attempted to identify patient groups that could avoid radiation therapy (RT). We investigated the recent surgical management of DCIS in Australia and New Zealand (ANZ) and evaluated the likely rates of RT delivery dependent on differing low risk predictive criteria compared to actual practice.

Method

The BreastSurgANZ Quality Audit identified patients with DCIS from 2018 to 2022. Data were analysed on multiple DCIS characteristics as well as postoperative RT recommendations. Existing potential RT avoidance characteristics, low risk classification criteria (LRCC) and RTOG 9804, were tested against the cohort.

Results

7790 cases were analysed with 5323 (68.33 %) undergoing breast conservation surgery (BCS). There was higher median age, lower tumour grade and smaller size in the BCS group compared to mastectomy (p < 0.001). According to the BQA, 25.38 % of patients had RT omitted. Using LRCC, 1659 patients (31.17 %) could omit RT but only 760 (45.81 %) of those patients did. When using RTOG 9804 criterion, 1287 patients (24.18 %) could omit RT but only 447 (34.73 %) did. Of 3477 patients with neither low risk classifying characteristics, 553 (15.9 %) had no RT.

Conclusion

BCS is the preferred surgical management of DCIS in ANZ. Currently RT is omitted following BCS in 25 % of cases. Using LRCC and RTOG 9804 low risk classifiers there was inconsistent avoidance of RT, whereas RT was avoided in 15.9 % of higher risk patients. More consistent and transparent selection methods are desirable and currently genomic testing and clinico-molecular tools appears promising.