ESTRO meets Asia 2024 - Abstract Book

S75

Interdisciplinary – Breast

ESTRO meets Asia

109

Digital Poster

Ipsilateral breast cancer recurrences by age following electronic brachytherapy (NCT01644669)

Barbara S Schwartzberg 1 , Alam M. Nisar Syed 2 , Charles Wesley Hodge 3 , Bapsi Chakravarthy 4 , Craig Wengler 5

1 Surgery, Schwartzberg Center for Minimally Invasive Breast Surgery, Santa Rosa, USA. 2 Radiation Oncology, MemorialCare Health System, Long Beach, USA. 3 Radiation Oncology, Advent Health Florida Hospital, Orlando, USA. 4 Radiation Oncology, Vanderbuilt University Medical Center, Long Beach, USA. 5 Surgery, Cleveland Clinic Martin Health, Stuart, USA

Purpose/Objective:

Outcomes attributed to age differences in early-stage breast cancer treatment are multifactorial. Women at least 40 years old with biopsy-proven breast cancer were consented in a prospective single arm non-randomized multi institution clinical trial (NCT01644669) designed to determine the efficacy and outcome of single fraction intra operative radiation therapy (IORT) using disposable balloon electronic brachytherapy at the time of breast conserving surgery. Primary and secondary endpoints were ipsilateral breast tumor recurrences (IBTR) and breast cancer-related survival at median 5.0-year follow-up. Age cohorts were analyzed for differences in outcome at these endpoints.

Material/Methods:

Between 2012–2018, 1199 breast cancer patients at least 40 years old, with single lesion, cN0, invasive ductal carcinoma (IDC) or ductal carcinoma in situ (DCIS) no larger than 30 mm, were enrolled. All patients received single 20 Gy fraction IORT at the time of lumpectomy using a disposable balloon per protocol. Chart review included demographics, treatment, pathology, IBTR (recurrence in lumpectomy cavity/index quadrant), and survival. The Chi-Square test was used for statistical analysis.

Results:

1199 patients (mean age: 66 years, range 41 - 93 years) completed IORT treatment per protocol, with 976 patients having invasive cancer (IDC: 964 patients, invasive lobular cancer: 12 patients) and 223 patients being diagnosed with DCIS. At median 5.0-year follow-up, there were 42 (3.50%) IBTR (mean age: 66 years, range 45 – 88 years). Patient age and outcomes are shown in Table 1. Age cohort derived IBTR for invasive carcinomas were not statistically different (p= 0.3884). Young DCIS patients had statistically higher IBTR (p=0.007), attributable to intermediate/high grade lesions and endocrine therapy noncompliance. There was one breast cancer-related death in a 79-year-old woman, for a breast cancer-related survival of 99.9%.

Conclusion:

At mean 5.0-year follow-up, the 1199 breast cancer patients, mean age 66 years, successfully treated with single 20 Gy fraction IORT per protocol using disposable balloon electronic brachytherapy were found to have a IBTR of 3.50% and breast cancer-related survival of 99.9%. The IBTR and breast cancer-related survival observed in this trial are similar to those reported in peer-reviewed IORT published data and to breast cancer treatments using whole breast radiation therapy (1). IBTR is not age-dependent for IDC patients otherwise meeting IORT inclusion criteria. Young patients with intermediate/high grade DCIS should be considered on an individual basis.