Are There Regional Differences in Survival Rates of Metastatic Breast Cancer?

Survival of patients with metastatic breast cancer has improved substantially over recent decades, but a new study shows that there is substantial regional variation in survival and in the improvement in survival.

“Variation in breast cancer recurrence and survival may be influenced by age, race, access to care, insurance coverage, socioeconomic status, geographic area of residence (urban/rural or metropolitan/nonmetropolitan), and timely diagnosis and treatment,” wrote study authors led by Judith A. Malmgren, PhD, of the University of Washington in Seattle.

The study compared data from the Surveillance, Epidemiology, and End Results (SEER) database that included breast cancer-specific survival (BCSS) by region with an institutional cohort in order to estimate variation by region. It included patients who were diagnosed with a first primary, de novo, stage IV breast cancer between the ages of 25 and 84 years between the years 1990 and 2011. The results were published online ahead of print on October 22 in Cancer.

The cohort included 12,121 patients in the SEER 9 region without Seattle-Puget Sound (S-PS), as well as 1,931 patients in that S-PS region alone and 261 patients in the institutional cohort from S-PS. The rate of 5-year BCSS in the SEER 9 without S-PS region improved from 19% in 1990 up to 26% in 2011 (P < 0.001). Among patients in the institutional cohort with stage IV breast cancer, the 5-year BCSS improved by 27% over that same period, from 29% up to 56%. Among those in the S-PS region, the improvement seen was 14%, from 21% up to 35%.

On a proportional hazards model, several factors were associated with better survival. These included recent diagnosis year, chemotherapy, surgery, and age under 70 years. In the SEER 9 cohort, additional factors that were associated with better survival included white race and positive hormone receptor status, as well as living in the S-PS region; the latter factor had a hazard ratio for BCSS of 0.87 (95% CI, 0.84-0.90). The risk for breast cancer death decreased between 2005 and 2011 by 28% in the SEER 9 without S-PS cohort, compared with 43% in the S-PS region and 45% in the institutional cohort.      

“It appears from these results that we may be at a crossroads for MBC treatment and survival,” the authors wrote. “Access to appropriate, timely, and up‐to‐date diagnosis, care, treatment, and surveillance could turn this fatal disease into a chronic and treatable phenomenon, depending on patient factors, molecular subtype, and insurance capacity to pay for treatment.”

The differences in survival and improvement by region show that improving access to care and other disparities is likely necessary to close some of the gaps seen in the data. “Strategies to educate the broader population and improve access to early diagnosis and screening, new drugs and drug combinations, and clinical trials will be critical if we are to reduce the disparities seen here and allow all to benefit from the significant advances that continue to be made,” the concluded.

References:

Metastatic breast cancer survival improvement restricted by regional disparity: Surveillance, Epidemiology, and End Results and institutional analysis: 1990 to 2011
Judith Malmgren-Gregory Calip-Mary Atwood-Musa Mayer-Henry Kaplan - https://onlinelibrary.wiley.com/doi/full/10.1002/cncr.32531