Breast Cancer

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TU_5_3370 - Long-term Subsequent Breast Cancer Risk and Overall Survival in Older Women with Estrogen Receptor Positive Early Stage Breast Cancer Treated in a Community Health Plan

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

Long-term Subsequent Breast Cancer Risk and Overall Survival in Older Women with Estrogen Receptor Positive Early Stage Breast Cancer Treated in a Community Health Plan
D. Jiang1, J. Chen1, X. Xu2, Y. Tian2, C. Avila2, and R. Haque2; 1Kaiser Permanente Los Angeles Medical Center, Los Angeles, CA, 2Kaiser Permanente Southern California, Pasadena, CA

Purpose/Objective(s): For older patients with early stage estrogen receptor positive (ER+) breast cancer after lumpectomy, omitting adjuvant radiation therapy may be an option that does not affect long term outcomes. We examined long-term outcomes including subsequent breast cancer (SBC) events (locoregional recurrence, new contralateral breast cancer, breast cancer metastasis, or breast cancer death), overall survival (OS), and breast cancer-specific mortality (BCSM) for this subset of patients.

Materials/Methods: We conducted a cohort study of women ≥65 years old in an integrated healthcare delivery system diagnosed with their first primary early stage breast cancer between 1997 and 2007 who were followed through January 1, 2017. Women with ER+ tumors ≤ 3cm with no lymph node involvement who underwent lumpectomy were identified from our SEER-affiliated cancer registry. Patients were stratified into four treatment groups: adjuvant radiation therapy (RT) only, hormone therapy (HT) only, both RT+HT (RT/HT) and lumpectomy only (NoRT/HT). SBCs were identified with a validated automated data algorithm applied to the electronic health record databases supplemented by manual review of pathology reports. Death dates and causes were extracted from state and national death databases.

Results: A total of 470 women matched our inclusion criteria. Tumor size, HER2 status, grade, pathologies were similar across the treatment groups. We identified 107 SBC events during the 20 years of study follow-up (median 9.4 years). In Kaplan-Meier analyses, the risk of SBC (p=0.34) and BCSM (p=0.98) were similar in all treatment groups. Overall mortality was worse in the NoRT/HT group when compared to the three other adjuvant treatment groups (p=0.02). In the subset of patients (n=315) with pathology reports, 44 women (13.9%) developed loco-regional recurrence, distant metastases, or a second primary breast cancer. The risk of distant metastases was 2.2%. Recurrence was in an unknown location in 3.2% of patients. The risk of locoregional recurrence was low in all four groups: HT+RT 0.6%, HT 3.0%, RT 2.4%, and 4.4% in NoRT/HT.
Adjuvant treatment SBC5 years SBC10 years OS5 years OS10 years BCSM5 years BCSM10years
NoRT/HT (n=76) 4.0% 16.6% 83.7% 54.0% 1.4% 5.0%
RT (n=67) 11.3% 17.7% 83.7% 65.3% 1.7% 6.2%
HT (n=91) 11.9% 15.0% 90.5% 71.0% 0% 6.2%
RT/HT (n=236) 7.5% 10.1% 89.5% 77.4% 2.4% 4.3%
Table 1: SBC, OS, BCSM for the four adjuvant treatment groups

Conclusion: Older patients with early stage ER+ breast cancer who did not receive adjuvant RT had similar long-term risks of SBC compared those who underwent RT. All groups had low rates of locoregional recurrence. Overall mortality was significantly worse for the lumpectomy alone patients without an increase in BCSM. RT use did not impact outcomes and may not be routinely required for these older patients.

Author Disclosure: D. Jiang: None. J. Chen: None. X. Xu: None.

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