Associations of circulating C-reactive protein and interleukin-6 with survival in women with and without cancer: findings from the British Women's Heart and Health Study.

BACKGROUND: Inflammation is associated with worse prognosis and survival in many cancers. Our aim was to investigate the associations of circulating C-reactive protein (CRP) and interleukin-6 (IL-6) concentrations with all-cause mortality in cancer patients and to determine whether any associations were specific to malignancy.
METHOD: We used data from the British Women's Heart and Health Study, a cohort of 4,286 women aged 60 to 79 years. We investigated the associations between CRP, IL-6, and survival in women with and without cancer using Cox regression and assessed the interaction between cancer status and these inflammatory markers to determine whether these associations differed according to cancer status.
RESULTS: Elevated CRP and IL-6 were associated with decreased survival in women with cancer [unadjusted hazard ratio per doubling of CRP, 1.22, 95% confidence interval (95% CI), 1.03, 1.46; and per doubling of IL-6, 1.52, 95% CI, 1.25, 1.86] and in women without cancer [CRP: 1.24 (1.12, 1.37); IL-6: 1.53 (1.35, 1.75)]. Adjustment for age, body mass index, physical activity level, socioeconomic position, HRT use, and tobacco smoking did not change these associations. After mutual adjustment, IL-6 but not CRP was independently associated with survival. We found no strong evidence that these associations differed between cancer patients and cancer-free women.
CONCLUSIONS: Elevated CRP and IL-6 concentrations were similarly associated with an increased risk of death in elderly women with and without cancer. Thus, in this group, these markers are likely to be indicators of non-cancer comorbidities rather than related to the malignancy itself.