Date of Award

January 2012

Document Type

Thesis

Degree Name

Medical Doctor (MD)

Department

Medicine

First Advisor

Cary P. Gross

Subject Area(s)

Medicine, Oncology, Public policy

Abstract

It is unclear how cost or survival outcomes for women with breast cancer in the Medicare population have changed over the past decade. In an effort to determine whether women receiving treatments are those who are likely to benefit from them, while avoiding treatments for patients unlikely to benefit, we analyzed 10-year trends in cost and survival and then focused on a particular intervention - adjuvant radiation therapy (RT) for stage I disease - to assess regional and systemic factors associated with overuse.

Women with stage I-III breast cancer diagnosed during two eras (1994-1996 and 2004-2006) a decade apart were selected from the linked SEER-Medicare database and matched to control patients without cancer. The primary outcomes were cancer costs during the initial phase of care and three-year survival rates; five-year survival rates were assessed among the subgroup with sufficient follow-up. To analyze variation in RT use, women diagnosed with stage I disease in 1998-2007 who received breast-conserving surgery (BCS) were selected and their predicted life expectancy (LE) was estimated based on age and comorbidity; LE categories were validated separately. We evaluated patient, physician and regional factors for their association with RT across strata of LE using a three-level hierarchical logistic regression model. Risk-standardized treatment rates (RSTRs) for receipt of RT were calculated according to primary surgeon and region.

There were 11,133 women diagnosed during 1994-1996, and 10,811 women diagnosed during 2004-2006. For women with stage III disease median cancer-related inflation-adjusted costs increased from $18,107 to $32,598 (P=.001). For stage II, costs rose from $12,335 to $17,396 (P<.001); for stage I, costs rose from $10,522 to $12,979 (P<.001). Survival improved significantly for women with stage III disease, rising from 58.0% to 68.1% (P<.001), whereas patients with stage II disease had no change in three-year observed survival (81.9% to 83.4%, P=.08). No difference was noted in stage I disease (91.3% to 91.8%, P=.27). When compared with matched controls, significant increases in both three- and five-year relative survival were noted only among women with stage III cancer. In assessing variation in RT use, 43.6% of the 2,253 women with a short LE received RT, compared to 90.8% of the 11,027 women with a long LE. Among women with a short LE, the probability of receiving RT varied substantially across primary surgeons, with the RSTRs ranging from 27.7% to 67.3% (mean 43.9%). There was less variability across geographic regions, with regional RSTRs ranging from 42.0-45.2% (mean 43.6%). Women with a short LE were more likely to receive RT when living in areas with a high radiation oncologist density (OR 1.59 for high vs. low radiation oncologists per 100,000; 95% CI, 1.07-2.36). For women with a long LE, the variation according to the primary surgeon ranged from 76.3% to 96.5% (mean 90.3%).

Costs related to breast cancer care have risen substantially in the Medicare population, and significant improvements in survival have been noted for women with stage III disease. Many women with a short LE receive adjuvant radiation after BCS, and the operating surgeon exerts a substantially stronger influence on the use of adjuvant radiation than geographic region.

Share

COinS