Why the Scandinavian prostate cancer study doesn’t translate to the U.S.

Lots of news coverage about a Scandinavian prostate cancer study.  Here’s a guest post on the study from Richard M. Hoffman, MD, MPH, Professor of Medicine at the University of New Mexico School of Medicine, and Staff Physician in the New Mexico VA Health Care System.  He has done story reviews and written blog posts on this site in the past. He has worked to develop shared decision making tools for prostate cancer screening and treatment of localized prostate cancer.

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This week the 23-year follow up data from the Scandinavian Prostate Cancer Group Study Number 4 (SPCG-4) was published in the New England Journal of Medicine.  The landmark SPCG-4 study was the first to show that men with localized cancers (confined to the prostate) had a survival benefit if they underwent radical prostatectomy surgery compared to watchful waiting (no active treatment).  Study results, first published in 2002, have consistently shown that the surgical group had a lower risk for dying from prostate cancer and developing metastatic disease than the watchful waiting group, and the most recent report also showed a lower risk for death from any cause.

For me, the study raises 2 important issues relevant to prostate cancer in the United States.  The first point is that PSA screening became widespread in the US in the early 1990s—a decade before the first SPCG-4 publication.   Perversely, the American way was to expend considerable resources to promote screening efforts to find cancers…before knowing whether these cancers could be successfully treated.  The second point is that the SPCG-4 results are not readily translatable to US practice.  Only 5% of the study cohort had cancers detected by screening PSA—the rest either had symptoms and/or a palpable tumor.  In the US, a substantial proportion of men with PSA-detected cancers have microscopic disease—which may never cause problems during a man’s lifetime.  The US Prostate Cancer Versus Observation Trial (PIVOT) also evaluated surgery vs. watchful waiting.  However, PIVOT, which mostly enrolled men with PSA-detected cancers, found no benefit for surgery.   Post-hoc analyses suggested that only the small proportion of men with higher-risk cancers (based on PSA and the microscopic appearance of the cancer) seemed to have a survival benefit.  This suggests that most men with PSA-detected cancers—the great majority of whom undergo aggressive treatment–will experience only the potential harms of treatment without any expectation of experiencing a prostate-cancer survival benefit.

Although the U.S. Preventive Services Task Force has advised against performing PSA testing, hundreds of thousands of men are still being diagnosed each year with prostate cancer.  These men need to be aware that early detection and aggressive treatment might not be good for their health, particularly for men with low-risk microscopic cancers.  These men should consider strategies such as active surveillance (AS).  With AS, men are closely monitored and offered aggressive treatment only if there is evidence that cancer is progressing—which we now know from the SPCG-4 and PIVOT trials is when treatment is most likely to be beneficial.

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Publisher’s note:

A web search turns up some really unhelpful and misleading headlines on this study, such as:

• Prostatectomy still superior to watchful waiting over long term

• Surgery over watchful waiting better for younger prostate cancer patients

Stories in the Boston Globe, CNN.com, the Associated Press and the Los Angeles Times each included at least some semblance of caveats or independent assessment of the findings, although the latter’s headline – “Surgery reduced risk of death by 44% in men with prostate cancer” – simply wasn’t helpful.

Some headlines – like the Globe’s “Study fuels prostate cancer debate” – followed the mammography-trial-du-jour framing of “conflicting, confusing” results.  Read beyond the headlines and you’ll see why that’s unhelpful for public comprehension.

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