Breast Cancer

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TU_7_3392 - Failure to Apply Eligibility Criteria per CALGB 9343 When Omitting Radiation Therapy Results in Excess Locoregional Failures in Elderly Breast Cancer Patients

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Failure to Apply Eligibility Criteria per CALGB 9343 When Omitting Radiation Therapy Results in Excess Locoregional Failures in Elderly Breast Cancer Patients
M. A. Whitmill1, A. H. Masters1, R. T. Hughes1, A. Merrill2, H. D. Klepin3, S. A. Melin3, K. M. Winkfield1, M. M. Howard-McNatt2, and D. R. Brown1; 1Department of Radiation Oncology, Wake Forest School of Medicine, Winston-Salem, NC, 2Department of Surgery, Wake Forest School of Medicine, Winston-Salem, NC, 3Department of Hematology and Oncology, Wake Forest School of Medicine, Winston-Salem, NC

Purpose/Objective(s): Previous trials have shown that older patients with early-stage, estrogen receptor (ER) positive breast cancer may be treated with lumpectomy followed by adjuvant endocrine therapy alone. Implementation of these findings is not well understood. We aim to compare clinical outcomes for elderly patients based on receipt of adjuvant radiotherapy (RT) and identify potential risk factors which may better inform the decision to omit radiotherapy when appropriate in this population.

Materials/Methods: In this IRB-approved study, 245 women with breast cancer who received lumpectomy at our institution between 2011-2017 and were at least 70 years old at the time of diagnosis were identified. Patients with metastatic disease, prior history of cancer, bilateral breast cancers, DCIS, or <6 months of follow up were excluded. Demographics, treatment and outcome data were obtained from the medical record. Patients were stratified by eligibility for omission of RT per CALGB 9343. Overall survival (OS), locoregional recurrence-free survival (LRRFS), and disease-free survival (DFS) were estimated using the Kaplan-Meier method and compared using the log-rank test. Age, race, Charlson comorbidity index, receptor status, grade, LVSI, axillary surgery, radiotherapy, chemotherapy, and CALGB eligibility were evaluated as predictors of survival using Cox proportional hazards.

Results: In total, 123 patients were eligible for inclusion. Median clinical follow-up was 26 months (range, 6-80). Forty-eight (39%) patients received radiotherapy and 75 (61%) did not. Age (p=.03) and frequency of PR positivity (p=.03) were significantly higher in the no RT group. LVSI (p=.03) and node-positivity (p=.01) were more frequent in the RT group. Seventy-seven (63%) patients received adjuvant endocrine therapy, of which 83% completed 2 years and 75% were adherent at last follow-up; 16 (13%) received adjuvant chemotherapy. CALGB criteria for omitting radiation was met in 73 (59%) patients; of these, 54 (72%) did not receive RT. Fifty (41%) patients did not meet CALGB criteria, and 29 (60%) of them received radiotherapy (p<.01). Of CALGB-eligible patients, 3-year LRFFS was 94% and 90% in patients who did and did not receive RT, respectively (p=.19). Of those not eligible for omission of RT, 3-year LRRFS was 100% and 73% with and without RT, respectively (p=.02). Multivariate analysis identified age associated with LRFFS (HR=1.17, p<.01) and comorbidity index associated with DFS (HR=1.70, p<.01) and OS (HR=1.92, p<.01).

Conclusion: In this single-institution study, the omission of radiotherapy in women who were not eligible for the omission of radiotherapy per CALGB 9343 was associated with significantly worse 3-year LRFFS. Age and comorbidity were identified as predictors of LRRFS, DFS and OS. Further investigation of the impact of radiotherapy in advanced-age breast cancer patients is warranted.

Author Disclosure: M.A. Whitmill: None. A.H. Masters: None. R.T. Hughes: None. A. Merrill: None. K.M. Winkfield: Chair, Health Disparities Committee; American Society of Clinical Oncology. M.M. Howard-McNatt: Vice Chair CME Committee; Society of Surgical Oncology.

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