Long-term health-related quality of life in prostate cancer - frequency and importance of side-effects of primary treatment and the implication for the evaluation of prostate cancer screening
2000 - 12 / 2004
Aims: The purpose of the study is threefold: 1. to determine the prevalence of permanent side-effects (urinary, sexual, and/or bowel dysfunction) of primary treatment (prostatectomy, radiotherapy) of localized prostate cancer in the long-term; 2. to investigate the relationship between the permanent functional side-effects and health-related quality of life; 3. to decide on a well-argued inclusion of the side-effects of primary therapy in the overall evaluation of favorable and unfavorable health effects of prostate cancer screening. The Rotterdam study on the health-related quality of life effects of prostate cancer screening showed no evidence that prostate cancer screening itself induces important health status effects in the short term. Screening, however, inevitably induces excess primary treatments, for example because small low-grade cancers are found and treated that otherwise would not have become clinically diagnosed because the subject would have died from another cause before (s)he would have experienced symptoms. To enable the inclusion of the unfavorable side effects of 'excess' primary treatment of localized prostate cancer in the overall evaluation of prostate cancer screening, valid estimates of the frequency and importance of these side-effects regarding health-related quality of life in general are needed. A prospective cohort study including 400 prostate cancer patients (screen-detected or clinically diagnosed) from 4 Rotterdam hospitals was started in 1996. First results showed important proportions of men having urinary, sexual or bowel dysfunction at 9 (radiotherapy) or 11 (prostatectomy) months after primary treatment, and a seeming 'discrepancy' between these disease-specific findings and generic health-related quality of life scores. The latter result causes serious problems regarding how to include the induced harm from 'excess' treatment in the evaluation of prostate cancer screening. Research plan: The study builds mainly on the infrastructure of the cohort study. The plan of investigation includes: 1. assessment of the long-term consequences of primary treatment, by health-related quality of life assessment four years after baseline in the original cohort; 2. assessment of differences in relative values attached to permanent health states occurring after primary therapy of localized prostate cancer by eliciting time trade-off values from 50 prostate cancer patients with permanent functional side-effects, 50 age-matched healthy control men, and 50 physicians (urologists, radiotherapists, general practitioners); 3. exploration of the 'discrepancy' between generic measures and disease-specific results. Hypotheses relate to the phenomenon of 'response shift' (changes in internal standards, values or QoL concept induced by primary treatment of localized prostate cancer) and insensitivity of the SF-36 and the EQ-5D (both generic measures for health-related QoL) for urinary, sexual and/or bowel dysfunction. To explore empirical assessment of response shift, about 50 patients with localized prostate cancer will be included in a new cohort study. Additionally, two qualitative studies will be conducted among patients from the 'old' cohort and age-matched control men, the first addressing the subjects' understanding of the contents of SF-36 and EQ-5D items, and the second the relative internal value of symptoms in relation to survival, general health status and general quality of life; 4. if different values will be found in 2, comparative, analyses this will show how these differences influence the evaluation of prostate cancer screening. The results will be discussed in an iterative procedure with clinicians and specialists in cost-effectiveness analysis to underpin the decision on what values on the side-effects of primary treatment are to be included in the overall evaluation of prostate cancer screening. Results and relevance for cancer research: The relevance for cancer research is twofold. First, the study will provide more certainty about an essential variable in the evaluation of the public health effects of prostate cancer screening. Secondly, the study will provide new insights into methods for empirical assessment of response shift, the suitability of generic measures to assess health-related quality of life in (prostate) cancer patients, and the effect of specific disease experience (none, as a patient, or professionally) on values of health states.