PROSTABLOG NZ: The debate within medical circles about the benefits – or not – of mass screening for prostate cancer just got a little more foggy in NZ.
Parliament’s Health Select Committee inquiry into prostate cancer was due today to hear from Lannes Johnson, medical director for the Harbour Health PHO, who – if a report in last week’s NZ Doctor magazine/website is to be believed – would enthuse about the results of a “new” study just released from Sweden.
Prostablog reported (also somewhat breathlessly) on the Göteborg study back in July after it appeared in Lancet Oncology, pointing to commentary by Mike Scott at the New Prostate Cancer Infolink.
Despite the positive tone of the NZ Doctor article – the majority of whose sources depicted the study as proof that population-based screening is fully justified – Scott’s analysis does not support that.
And neither does an editorial (represented by one paragraph in the NZ Doctor article) by Cambridge University’s Prof David Neal, which appeared at the time of the Lancet Oncology report.
After rehearsing the contents of the Goteborg study, Scott had this to say:
- This study appears to show clearly that, in a screening-naïve population of men aged between 50 and 70 years of age, biannual PSA testing can lower the risk for prostate cancer-specific mortality by at least 40 percent.
- In addition, the study shows that the proportion of patients diagnosed with prostate cancer and requiring hormone therapy in the screening group (103/1,138 or 9.1 percent) was much less than half that of the patients in the control group (182/718 or 25.3 percent), implying that early detection also reduced the risk for metastatic disease.
- However … the study also shows clearly that (at 14 years of follow-up) biannual PSA screening has no impact whatsoever on the overall mortality rate in the same population.
We are therefore potentially faced with the difficult question of whether mass, population-based screening that does affect disease-specific mortality but does not affect overall mortality is justifiable based on the costs, the effort, and the potential harms to the men who are over-treated.
The single most important fact about this study, as far as The “New” Prostate Cancer InfoLink is concerned, is that it finally has provided us with a highly structured, ongoing assessment of the potential value of mass, population-based screening for prostate cancer in a previously screening-naïve population.
The study also includes full treatment information on all men diagnosed with prostate cancer over the course of the study.
This means that at last we have a real baseline against which to assess the data from all other screening studies, and we can use this baseline to recognize the inherent problems of the PLCO and ERSPC studies, which include short follow-up (to date) in both studies, variation in protocols (within the ERSPC cohorts), and data adulteration resulting from PSA testing among the “unscreened” patient cohort (in the PLCO study).
The data from the Göteborg study may still not provide a convincing rationale for mass, population-based screening based on use of the PSA test, but it certainly does set the standard for what must be expected from any new test that may come along and show promise as a true screening test for prostate cancer in the future.
The one regrettable fact about this study is that if it had included just one additional age cohort (of men born between 1945 and 1950), we might have been able to gain real insight over time into the benefits of even earlier detection for a period of up to 30 years.
A much more cautious note here, then, than these comments in NZ Doctor:
“The Government can hardly say they won’t screen for prostate cancer if the science supports it,” Dr Johnson says, referring to an ongoing Parliamentary inquiry into the early detection and treatment of prostate cancer.
Auckland urologist Robin Smart says the bottom line for him is that the study shows prostate cancer screening could prevent 300 of the 600 deaths from prostate cancer that occur every year in New Zealand. “All of the results strongly suggest that PSA screening is a really good idea,” Dr Smart says.
NZ Doctor concluded:
The results of the Göteborg trial are due to be presented to the Health Select Committee next week (today, September 15) as part of its inquiry into prostate cancer. Dr Johnson will talk about the results during a presentation by Harbour Health on PHO capability for reducing the burden of cardiovascular disease, smoking and diabetes.
Let’s hope the committee takes the time to read more widely about the study.