Cancer survival rates vary across international borders

Coleman MP. Lancet. 2010;doi:10.1016/S0140-6736(10)62231-3.

Despite increases in survival rates of four cancer types during a recent 12-year period, variations in survival rates by year were observed in the six countries studied, according to current findings.

Cancer survival is an important measure of the effectiveness of health care systems, according to researchers from institutions on several continents. They hypothesized that regional and international differences in cancer outcomes may be associated with preventable deaths.

The aim of the current study was to evaluate disparities in survival rates and potentially provide cancer-control policymakers the tools to eliminate these disparities.

The findings were taken from population-based cancer registries representing 12 jurisdictions in six countries. The analysis involved more than 2.4 million adults diagnosed with primary colorectal, lung, breast or ovarian cancer from 1995 to 2007. The final follow-up was Dec. 31, 2007.

Common protocols overseen by external evaluators were employed to ensure quality control of analyzed data. The primary analyses were estimates of 1-year and 5-year relative survival rates.

Adjustments for background mortality by age, sex and calendar year were made for the 252 complete life tables that constituted the analysis. The resulting age-specific and age-standardized findings include not only 1- and 5-year survival rates, but also conditional 5-year survival rates through the first anniversary of diagnosis.

Cancer incidence and mortality trends from 1985 to 2005 also were investigated.

Improvements in relative survival were observed for all four studied cancers in all jurisdictions between 1995 and 2007.

Persistently higher survival rates were observed in Australia, Canada and Sweden; intermediate survival rates were observed in England, Northern Ireland, Norway, Wales and the lower regions of Denmark, particularly within 1 year of diagnosis and for patients aged 65 years or older. For all of these regions and countries, the researchers noted that survival rates were within 2% to 3% of each other.

All six countries experienced increased colorectal survival rates at a similar pace.

Differences in breast cancer survival rates across nations and jurisdictions narrowed from 9% to 5% at the 1-year mark. Five-year breast cancer survival rate differences narrowed from 14% to 5% by country or region.

Similar narrowing of international differences in survival rates were not observed for the other cancers.

The international range of colorectal cancer survival rates narrowed only for patients aged 65 years or older, by 2% to 6% at the 1-year mark and 2% to 3% at the 5-year mark.

“Up-to-date survival trends show increases but persistent differences between countries,” the researchers wrote. “Trends in cancer incidence and mortality are broadly consistent with these trends in survival. Data quality and changes in classification are not likely explanations.”

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