11 aug 12 treating prostate cancer
- 1. Treating Prostate Cancer No benefit from radical prostatectomy for men with low risk disease. Introduction When it comes to research papers sample size matters, so when Journals report large studies where patients are randomised to treatment or no treatment, then I tend to the details of the paper. The research study is the prostate cancer intervention verses observation trial (PIVOT) and the sample size is a sexy 731. Reference – Parker C., 2012 Treating Prostate Cancer.BMJ, 4th August, Vol 345, pp9 Précis of article There are several ways to look at a paper – I’m old fashioned, so I need to know whether to read the paper closely. The title confirms that the paper is clinically important, so I look to the randomisation. 15% of men randomised for surgery did not have surgery and 20% of those randomised to watchful waiting did receive surgery. So the study is still large with over 500 patients. Next the findings: 2.9% of patients randomised to surgery had a reduction in mortality at 12 years (there is a large confidence interval of0.71 to 1.08). This tells us two things – surgery may have a small beneficial impact on mortality and that even this study is not sufficiently sexy to tell us confidently that surgery is beneficial for patients. However, research, like an onion, has layers of complexity. This is evidenced in subgroup analysis - PIVOT had 279 men at low risk from prostate cancer (less than 3% risk of mortality after 12 years). How did these men fair? Well, sometimes interpreting research is opaque – sometimes findings that are not statistically significant are highly clinically significant. Patients randomised to watchful waiting did marginally better (1.15 – confidence range 0.8 to 1.66). Discussion Neither of these studies can tell us the numbers of patients that need to receive or not receive treatment to save a life! But I said that the sub-group analysis was highly clinically significant. We have established that PSA =
- 2. prostatic specific antigen as a poor measure (surrogate marker) of prognosis. The use of PSA measurement has led to a tripling of the incidence of prostate cancer since the 1970s. Too many patients with early prostatic carcinomaare unlikely to have benefited from radical prostatectomy. Questions to ask your urologist: 1. Are there any better tests that would establish my need for surgery? The higher the risk the more you are likely to benefit from surgery. There are several promising tests in the pipeline. 2. Is my risk of mortality from prostate cancer less than 3% at 12 years? If the answer is yes, then you are unlikely to benefit from radical prostatectomy. 3. If your urologist suggests you have a biopsy: then ask him whether even if he found that the biopsy harboured Gleeson 7 prostatic disease, would surgery be more beneficial than watchful waiting? You guessed surgery would be unlikely to be beneficial – but at this point your urologist would seriously consider not offering you the biopsy. 4. Your urologist knows much more than I do about this (he is the specialist while I’m the generalist)– if he recommends surgery it is likely to be the evidenced-based treatment. Nigel Roper