From OncoLog, November-December 2011, Vol. 56, Nos. 11-12
Prostate Cancer Screening
The U.S. Preventive Services Task Force recommendation against prostate-specific antigen (PSA)–based screening for prostate cancer in men with no symptoms of the disease has led to uncertainty about the appropriate use of the PSA test.
“The proper use of PSA-based screening is a very nuanced issue that has been interpreted by the media as two extreme choices, which are no use of PSA-based screening or widespread use of PSA-based screening in uninformed populations,” said Christopher Logothetis, M.D., a professor in and chair of the Department of Genitourinary Medical Oncology at The University of Texas MD Anderson Cancer Center. “The task force does not advocate either of these choices. The task force is advocating a sophisticated use of the PSA test based on symptoms and on the level of concern shared by the physician and the patient.”
The task force’s recommendation was made on the basis of two large studies—one in the United States and the other in Europe—showing that PSA-based screening was associated with the overdiagnosis and overtreatment of prostate cancer but did not significantly affect 10-year prostate cancer–specific mortality rates.
However, Dr. Logothetis pointed out that one should not expect a difference in 10-year mortality rates between men who received PSA-based screening and men who did not because most prostate cancers progress slowly. “This disease can take 20 years to result in death, so the timing of these studies is better for detecting excess treatment than for detecting a difference in mortality rates,” he said. “The very nature of the disease indicates that the impact of PSA-based screening on mortality is not going to manifest itself for another 10 years.”
Benefits and limitations
While the potential survival benefits of PSA-based prostate cancer screening remain unknown, the potential risk of unnecessary treatment is well documented. “The data are unquestioned that show PSA-based screening has resulted in patients getting treatment who would have done well in the absence of any treatment,” Dr. Logothetis said, “and these treatments are not innocuous.”
Dr. Logothetis said that many physicians involved in prostate cancer treatment and research have a view that prostate cancer awareness and the widespread use of PSA-based screening have resulted in stage migration—an increasing number of newly diagnosed patients have prostate cancer that is localized and amenable to surgery. “An initial diagnosis of prostate cancer manifested as widespread disease is becoming increasingly unusual,” he said. “Because many physicians interpret this as an objective benefit of PSA-based screening, they are reluctant to stop screening.”
Informing the patient
The task force did not evaluate the use of the PSA test for disease surveillance after diagnosis or treatment of prostate cancer, nor did it study PSA-based screening as part of a diagnostic strategy in men with symptoms that indicate prostate cancer. “PSA-based screening should be recommended for patients who have symptoms of prostate cancer,” Dr. Logothetis said.
MD Anderson recommends that men age 45 years or older with one or more risk factors for prostate cancer discuss screening with their physicians. Risk factors for prostate cancer include African American race or having a first-degree relative who has had prostate cancer. Men age 50 years or older with no symptoms or risk factors for the disease should also discuss screening with their physicians. If screening is desired, men should have annual PSA tests and digital rectal exams.
Dr. Logothetis said that physicians should make sure patients understand that even if PSA levels are elevated and prostate cancer is confirmed by a biopsy, it is likely that no treatment will be necessary.
“My interpretation of the task force’s recommendation is that widespread PSA-based screening of patients who are not informed about the wise use of this tool should be avoided, but the use of PSA-based screening by physicians who have informed their patients about the significance and consequences of an elevated PSA level should be continued,” Dr. Logothetis said. “If we think of it in those terms, we can reduce the risk of overtreatment.”
For more information, contact Dr. Christopher Logothetis at 713-563-7210.