Abstract PO4-17-05: Patterns of care: radiotherapy after breast conserving surgery and the use of endocrine therapy for screen-detected ductal carcinoma in situ (DCIS) in the UK
Authors: Clements Karen , Dodwell David , Sawyer Elinor , Cutress Ramsey , Sharma Nisha , Shaaban Abeer , Thompson Alastair 
Published: May 2024

Abstract
Background
The use of adjuvant radiotherapy (RT) and endocrine therapy (ET) in the management of pure ductal carcinoma in situ (DCIS) remains controversial. We investigate how the use of adjuvant RT after breast conserving surgery (BCS) and use of adjuvant ET (in BCS and mastectomy patients) has changed over time.
Methods
A prospective cohort SQL database of 11,284 patients (the Sloane Project) diagnosed 2003-2012 with screen-detected DCIS in the UK was interrogated for use of adjuvant RT and ET over time and association with factors reported to be predictive of recurrence (patient age, DCIS nuclear grade, size, comedo necrosis, resection margins), as well as institution of surgery, travel time to radiotherapy facility, Index of Multiple Deprivation and outcome (provided by the National Disease Registration Service, NDRS). RT data by site were confirmed with more recent data from the National Audit of Breast Cancer in Older Patients (NABCOP), which looked at patterns of care and outcomes for women aged 70 years and over, compared with those aged 50-64 in England and Wales.
Results
Among the 7,949 women (70.6%) treated by BCS, post-operative adjuvant RT was given to 4,939 (62.1%); RT use after BCS increased over time (R2 =0.92; p&lt; 0.01). RT use was associated with year of diagnosis (p &lt; 0.01), younger age at diagnosis (p &lt; 0.01), larger DCIS size (p &lt; 0.01), presence of comedo necrosis (p &lt; 0.01), higher nuclear grade (p &lt; 0.01) and presence of microinvasion (p &lt; 0.01). Adjusted analyses showed the most significant factor for RT after BCS was the surgery institution. Travel time to RT facility, Index of Multiple Deprivation and final radial margin were not associated with RT use. When compared with the more recent data from the NABCOP, a marked variation in radiotherapy use across hospitals remains. Ipsilateral recurrence rate varied significantly by hospital, with some of the difference associated with RT utilisation. ET was prescribed in 1313 women (12%), more often following BCS than mastectomy (p &lt; 0.001), with significant variation by institution and a decline in the use of ET over time.
Conclusion
Marked geographic variation in the use of RT and ET after surgery for DCIS persists in the UK and is likely due to physician choice rather than other factors such as travel times to RT facilities. This is contributing to geographic variation in ipsilateral recurrence rates, suggesting the need for adoption of more authoritative guidelines to support clinical decision-making. Consistent national practice could provide auditable performance standards for adjuvant therapy of screen detected DCIS and contribute to more uniform patient care.
Citation Format: Karen Clements, David Dodwell, Elinor Sawyer, Ramsey Cutress, Nisha Sharma, Abeer Shaaban, Alastair Thompson. Patterns of care: radiotherapy after breast conserving surgery and the use of endocrine therapy for screen-detected ductal carcinoma in situ (DCIS) in the UK [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO4-17-05.