A Swedish population-based observational study has shown that comorbidity is a significant factor in other-cause but not prostate cancer–specific mortality after adjustment for patient, tumor, and treatment factors among men with prostate cancer. The findings were reported in the Journal of Clinical Oncology by Rajan et al.
The study involved data on 118,543 men in Sweden who were diagnosed with prostate cancer from 1998 to 2012. The median follow-up was 8.3 years until death from prostate cancer or other causes. Patients were categorized by patient characteristics, tumor characteristics, and treatment type and were stratified according to Charlson comorbidity index (CCI; 0, 1, 2, or ≥ 3).
Associations of Comorbidity With Outcomes
In an unadjusted analysis, increased comorbidity was associated with significantly higher cancer-specific (hazard ratio [HR] = 1.99, P < .001, for CCI ≥ 3 vs 0) and other-cause mortality (HR = 5.62, P < .001, for CCI ≥ 3 vs 0), with hazard ratios also being significant for CCI of 1 (HR = 1.53, HR = 2.43) or 2 (HR = 1.56, HR = 3.26) vs 0 for both outcomes. After adjustment for patient and tumor characteristics, the significant effect of comorbidity on cancer-specific mortality was lost for CCI 1 (HR = 1.02) and 2 (HR = 1.03) vs 0 but persisted for CCI ≥ 3 vs 0 (HR = 1.15, P < .001) and was maintained for each comparison for other-cause mortality (HRs = 1.53, 2.06, and 3.33 for CCI 1, 2, and ≥ 3 vs 0; all P < .001). After additional adjustment for treatment type, no significant association with CCI index was observed for cancer-specific mortality, whereas all three comparisons remained significant for other-cause mortality (HRs = 1.49. 1.99, and 3.16; all P < .001).
The investigators concluded: “This large observational study suggests that comorbidity affects other cause-mortality but not [prostate cancer–specific] mortality after accounting for patient and tumor characteristics and treatment type. Regardless of radical treatment type (radical prostatectomy or radical radiotherapy), increasing comorbidity does not seem to significantly affect the risk of dying from [prostate cancer]. Consequently, differences in oncologic outcomes that were observed in population-based comparative effectiveness studies of [prostate cancer] treatments may not be a result of the varying distribution of comorbidity among treatment groups.”
The study was funded by a joint Royal College of Surgeons/Cancer Research UK Clinician Scientist Fellowship in Surgery; Barts Charity and the Orchid Charity; the National Institute for Health Research Oxford Biomedical Research Centre; and grants from the Swedish Cancer Society, Stockholm County Council, and Swedish Research Council.
Prabhakar Rajan, MD, PhD, of Cancer Research UK Barts Centre, Queen Mary University of London, is the corresponding author of the Journal of Clinical Oncology article.
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