PCa-specific mortality not affected by comorbidity

Author(s):

Comorbidity does not affect prostate cancer-specific mortality, according to authors of a large prospective observational study of men in Sweden, published in the Journal of Clinical Oncology (2017; 35:3566-74).

Comorbidity does not affect prostate cancer-specific mortality, according to authors of a large prospective observational study of men in Sweden, published in the Journal of Clinical Oncology (2017; 35:3566-74).

“Regardless of radical treatment type [radical prostatectomy or radical radiotherapy], increased comorbidity does not seem to significantly affect the risk of dying from prostate cancer,” reported lead study author Prabhaker Rajan, MD, PhD, consultant urologist at Barts Health and University College London Hospitals NHS Trust and clinical senior lecturer in urology at Queen Mary University of London, and colleagues. “Consequently, differences in oncologic outcome that were observed in population-based comparative effectiveness studies of prostate cancer treatments do not seem to be a result of the varying distribution of comorbidity among treatment groups.”

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Comorbidities and their impacts on life expectancy can importantly influence prostate cancer treatment decision-making. Survival benefits for radical prostatectomy and radical radiotherapy emerge after a decade more, so guidelines recommend that these treatments not be undertaken in men with life expectancy of 10 years or less, the authors noted. Previous studies have yielded mixed outcomes for the effect of comorbidity on prostate cancer-specific mortality.

The authors sought to use a population-based observational national study of 118,543 men diagnosed with prostate cancer between 1998 and 2012, using data from nine national registries representing more than 98% of men diagnosed with prostate cancer in Sweden after 1998. Multivariate analyses were conducted using patient marital status and educational attainment, tumor characteristics (including serum PSA, tumor grade, and clinical stage), and treatment type. Patient data were stratified using the four-category Charlson comorbidity index: 0, 1, 2, or ≥3.

“After adjustments for patient and tumor characteristics, the effect of comorbidity on prostate cancer-specific mortality was lost but maintained for other-cause mortality,” the authors reported.

Next: Watchful waiting, ADT groups analyzed

Watchful waiting, ADT groups analyzed

A subsequent subset analysis for each treatment group found that among men in the watchful-waiting group, prostate cancer-specific mortality was associated with any comorbidity (Charlson index scores 1, 2, or 3+) versus no comorbidity (Charlson index score 0). However, this association disappeared when statistically adjusted for patient and tumor characteristics. A subgroup analysis of data for patients in the androgen deprivation therapy group found that a Charlson comorbidity index of ≥3 was associated with a modest 1.10 hazard ratio for prostate cancer-specific mortality compared to patients without comorbidities, both before and after adjusting for patient and tumor characteristics (p=.004 and .014, respectively).

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It is possible that cause of death misclassifications in the Swedish deaths registry, difficulty detecting relevant comorbid conditions, or early deaths from non-cancer causes might have affected the findings, the authors acknowledged.