The American Cancer Society is taking the lead in disputing a new Northwestern Medicine study which reported that new cases of metastatic prostate cancer have climbed 72 percent over the past decade. The Northwestern report’s authors go on to speculate on what might be contributing to the rise – the trend of fewer men being screened, the disease itself becoming more aggressive, or both.
Pointing at what they deemed to be a 92% increase over the decade in cases among men 55 to 69 years old, the Northwestern authors were concerned that the demographic believed to benefit most from prostate cancer screenings and the resulting early treatment were instead being diagnosed with a larger number of the most serious and incurable cases of the disease.
The paper was published on July 19 in Prostate Cancer and Prostatic Diseases, a journal from Nature. It was based on information gathered from the National Cancer Database of about 800,000 men from 1,089 facilities nationwide who had been diagnosed with prostate cancer between 2004 and 2013.
But not so fast, says Dr. Otis W. Brawley, Chief Medical Officer for the American Cancer Society (ACS). The central claim of the Northwestern report he says, that less PSA screening might lead to more advanced cancers, is based on analysis “far from adequate to answer that question sufficiently.”
The main flaw in the study, he points out, is that Northwestern did not look at the rate of prostate cancer diagnoses, relying instead on solely the raw number of cases that had occurred across the country. This ignores the more conventional means of evaluating such statistics, which is based on the number of cases for a certain number and within age and race sub-categories of people in the study.
“A rising number of cases can also be due simply to a growing and aging population, among other factors,” according to ASC’s Dr. Brawley. Dr. Christopher Filson of Emery University School of Medicine concurs, saying, “(The findings) may be true, but the way they looked at the question brings in too many possible alternative explanations.”
The New York Times also voiced skepticism, calling out Northwestern for the incendiary headline of its report – “Metastatic Prostate Cancer Cases Skyrocket” – as well as criticizing media outlets that essentially reprinted the Northwestern press release without mentioning the ACS reaction or seeking commentary from outside experts.
Prostate cancer screening continues to be the focus of spirited debate, with its advocates taking the position that it saves lives and detractors claiming it leads to unnecessary treatment of tumors in mild cases that would not have become life-threatening. In recent years the U.S. Preventive Services Task Force has changed positions and advised against screenings, saying the risks of treatment outweighed the benefits. But many doctors take the position that a drop in screening will lead to an increase of cases that are detected too late to be cured, particularly among African-American men who have a mortality rate from the disease that is 2-3 times that of the general population.
Despite admitting to the report’s “limitations,” the senior author of the study, Dr. Edward Schaeffer, a prostate cancer oncologist and the chairman of urology at Northwestern, said in a follow-up interview that he continues to believe that screening saves lives. He also said that his concern about more aggressive strains of prostate cancer continues, since higher PSA numbers among his patients was something he began to witness even prior to the start of the study.