Abstract P3-07-20: Survival comparative analysis of patients with invasive breast cancer treated by a military medical center and matched patients of the US general population

Abstract

Abstract BACKGROUND U.S. military beneficiaries differ from the U.S. general population with regards to access to health care as care is provided at no or much lower cost in the military health system. Other differences also exist. Many of these differences are known factors affecting invasive breast cancer outcomes. Thus it is desirable to conduct a comparative analysis of breast cancer patient outcomes between these two populations to find out whether there is any outcome difference, and if yes what the contributing factors are. METHODS We compared overall survival (OS), disease-specific survival (DSS), and 5-year OS and DSS rates in breast cancers between 399 patients from the Clinical Breast Care Project at the Walter Reed National Military Medical Center (CBCP-WR) and 1,000 sets of 1596 matched patients from the Surveillance, Epidemiology, and End Results (SEER) Program of the National Cancer Institute. All patients were diagnosed between 2001 and 2010. Each CBCP-WR patient was randomly matched to four SEER patients on six demographic and clinicopathologic variables (age at diagnosis in 5-year groups, race, diagnosis year, estrogen receptor (ER), progesterone receptor, and AJCC stage). RESULTS The CBCP-WR cohort had better survival than the SEER population. At the whole cohort level, the mean hazard ratios (HRs) from 1,000 matched comparisons for OS and DSS were 0.774 and 0.708, with mean log-rank P-values of 0.124 and 0.125. The numbers of 175 and 141 comparisons showing a log-rank P-value <0.05 out of the 1,000 tests were significantly higher than what would be expected from a random distribution of these P-values (P<0.00001, exact binomial test). By stratifying the cohorts we identified that this survival disparity was mainly contributed by patients with a diagnosis age ≥50 years (for DSS, mean HR=0.550, mean P=0.049, and 642 of 1,000 tests showed a P<0.05; for OS, mean HR=0.713, mean P=0.081, and 377 of 1,000 tests showed a P<0.05), but not by patients with a diagnosis age <50 years. The absolute differences in 5-year DSS rates were 4.4% (94.6% in CBCP-WR vs. 90.2% in SEER; mean P=0.010) for all matched patients and 4.8% (95.2% vs. 90.4%; mean P=0.015) for patients diagnosed at an age ≥50 years. Again there was no significant difference for patients diagnosed at an age <50 years. When stratified by race, ER, stage or grade, most of the patient subpopulations showed favorable 5-year OS and DSS rates in the CBCP-WR cohorts. CONCLUSION Overall, these results suggested that breast cancer patients, especially older patients seen in the CBCP-WR, carried more favorable outcomes than those from the general population. The findings warrant further analyses of the contributing factors, such as health care access, treatments, population characteristics, additional pathologic characteristics, and socioeconomic statuses, to this outcome disparity. The views expressed in this article are those of the author and do not reflect the official policy of the Department of Defense, or U.S. Government. Citation Format: Yuanbin Ru, Jianfang Liu, Jamie Leigh Campbell, Kangmin Zhu, Albert J Kovatich, Jeffrey A Hooke, Leonid Kvecher, Brenda Deyarmin, Audrey W Kovatich, Frank Cammarata, Hallgeir Rui, Richard J Mural, Craig D Shriver, Hai Hu. Survival comparative analysis of patients with invasive breast cancer treated by a military medical center and matched patients of the US general population [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P3-07-20.