Cancer: Lower SES translates into lower cancer survival in Canada

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Socioeconomic status (SES) remains associated with survival among cancer patients in Ontario, despite a universal healthcare approach, according to a study published online Aug. 2 in Cancer.

Christopher Booth, MD, of the Queen's University Cancer Research Institute in Kingston, Ontario, and colleagues sought to evaluate the impact of SES on stage of cancer at diagnosis and survival in Ontario, as “lower SES is associated with worsened cancer survival,” they wrote.

The researchers leveraged the Ontario Cancer Registry to identify all cases of breast, colon, rectal, non-small cell lung, cervical and laryngeal cancer diagnosed in Ontario from Jan. 1, 2003 to Oct. 31, 2007 at eight regional cancer centers. Based on community median household income reported in the 2001 census, Booth and colleagues divided the 38,431 patients according to quintile 1 (Q1) to quintile 5 (Q5), with Q1 representing the poorest communities.

The researchers evaluated the association between survival and SES, stage and age and used Kaplan-Meier methodology to determine overall survival and cancer-specific survival.

Booth and colleagues determined that there were very subtle differences in stage distribution by SES and attributed this finding to universal health coverage in Ontario, which may facilitate access to primary care physicians and cancer screening as this result conflicts with studies conducted in the U.S., they wrote.  

However, substantial gradients in five-year overall survival and three-year cancer-specific survival across Q1 and Q5 were noted for breast (7 percent absolute difference in overall survival), colon (8 percent overall survival), rectal (9 percent overall survival), non-small cell lung (3 percent overall survival), cervical (16 percent overall survival) and laryngeal cancers (1 percent overall survival).   

Moreover, adjustments for stage and age slightly diminished the survival gradient only among patients with breast cancer, the authors noted.

“Large and significant disparities in survival exist in Ontario despite universal healthcare,” determined Booth and colleagues. “Whereas stage of disease at diagnosis may account for a small portion of the survival gradient among patients with breast cancer, other factors, including differences in disease biology, comorbidity, access to therapy and quality of care, may have a greater impact on survival,” they stated.

The authors concluded that additional work is needed to better understand these factors and to develop strategies to reduce disparities in the outcome of patients with cancer.