From bad to worse: comorbidity severity and quality of life after treatment for early-stage prostate cancer.

Commonly used measures of comorbidity assess comorbidity number and type but not severity. We sought to evaluate the impact of comorbidity severity on longitudinal health-related quality of life (HRQOL) in men treated with radical prostatectomy (RP) or radiation therapy (RT) using the Total Illness Burden Index for prostate cancer (TIBI-CaP). We sampled 738 men with non-metastatic prostate cancer treated with RP or RT from the Cancer of the Prostate Strategic Urologic Research Endeavor registry. We examined the impact of comorbidity severity on generic and disease-specific HRQOL at baseline and at 6, 12, 18 and 24 months post-treatment. Men with worse TIBI-CaP comorbidity had significantly lower baseline and post-treatment HRQOL in all domains at all time points. In a multivariate model, men with moderate or severe TIBI-CaP comorbidity had significantly worse HRQOL scores at 12 and 24 months after treatment in all domains except sexual and urinary function (P<0.05); in these domains, severe comorbidity was predictive of lower HRQOL (P<0.05). Comorbidity groups had similar absolute declines in HRQOL from baseline to 6 and 24 months after treatment. Although comorbidity groups experienced similar long-term declines from baseline HRQOL after treatment, men with more severe comorbidity had significantly lower baseline scores and therefore poorer long-term HRQOL.