A new risk calculator may help men with high levels of prostate-specific antigen (PSA) — a marker of prostate cancer — to decide if they should undergo a prostate biopsy to determine if they have cancer.
The cancer risk calculator, developed by researchers at Kaiser Permanente Northern California, is specifically designed to calculate the risk each patient has of having either low- or high-grade cancer, or no cancer at all. It is designed for men with high PSA levels or who have had abnormal findings in a digital rectal exam.
The development and validation of the risk calculator was reported in “Prospective development of a prostate cancer risk calculator in a racially diverse population: The Kaiser Permanente Prostate Cancer Risk Calculator,” a study published in the journal Urologic Oncology.
For many years, physicians have debated whether men should have their PSA levels checked annually as part of a routine screening for prostate cancer.
The issue with PSA is that the test has a known risk of overdiagnosis. That means that many men who have high PSA levels may not have cancer, or may have a low-grade tumor that would be unlikely to cause serious issues. For some physicians, this risk of overdiagnosis outweighs the benefits the PSA test might provide in identifying high-grade cancers that ought to be treated aggressively as fast as possible.
“The PSA is not a great test because an elevated result doesn’t mean you have cancer, and even if you do it might be a low-grade cancer that will never grow any larger,” Joseph Presti, MD, adjunct researcher at the Kaiser Permanente Northern California Division of Research and first author of the study, said in a press release.
“With the calculator, the doctor can plug in information about the patient — age, race, family history for prostate cancer, body mass index, PSA level, number of prior negative biopsies, result of the rectal exam, prostate volume — and get results that can help the patient determine whether to undergo additional tests or have the biopsy,” Presti said.
To create the risk calculator, the researchers first gathered data from 2,967 men who had a prostate biopsy done at the Kaiser Permanente Northern California between May 2016 and November 2017. Data included information on their race and ethnicity, family history of the disease, results from a digital rectal exam (if and when performed), number of previous biopsies, and prostate volume.
The calculator was then built based on three statistical models that estimate the chances each patient has of having a biopsy showing the presence of a low- or high-grade cancer, or its absence. The models take into account the information previously gathered on each patient.
“What we want is for the calculator to hopefully decrease the number of men who undergo biopsy and thus decrease the number of slow-growing cancers detected that we would rather not find,” Presti said.
“We also want to decrease the number of men who have multiple biopsies that do not show cancer,” he added. “Ideally, we would only perform a biopsy on men with a significant risk of having an aggressive cancer that needs treatment.”
Among the men participating in the study, half (50%) were found to have cancer. From these, more than half (58%) had high-grade cancer.
Compared with Caucasians, African Americans had a higher risk of having both low- and high-grade cancers detected in a prostate biopsy. Meanwhile, Asians and Hispanics had a lower risk of having cancer detected in a biopsy.
In addition, men with a high number of previous biopsies that did not identify any type of cancer were less likely to receive a positive cancer diagnosis in subsequent procedures.
Further analyses showed that all three statistical models used to create the risk calculator fitted well with patient data, and were able to estimate, with reasonable precision, those who would develop cancer and those who would not.
Kaiser Permanente said its new calculator is the first to have been developed using a racially diverse population.
“The information it provides reflects racial and ethnic disparities in prostate cancer incidence and death,” the press release said, noting that Blacks are more likely than men of other races and ethnicities to be diagnosed with prostate cancer. Black men also are more likely to develop prostate cancer at a younger age — and are 2.5 times more likely to die of the disease — as compared with non-Hispanic white men.
“These findings support more aggressive screening for Black men,” the press release said.
The three models are now being tested in a larger group of patients at Kaiser Permanente who underwent a prostate biopsy after having abnormal findings on a digital rectal exam or very high PSA levels. Data from this external validation study of the risk calculator are expected to be published in 2021.
In the meantime, investigators are considering a prospective study to gather feedback from patients and healthcare providers regarding the usefulness of the risk calculator in their decisions to pursue additional testing.
“We think our calculator will provide valuable information for physicians in counseling patients with an elevated PSA who are considering prostate biopsy and may be useful in identifying patients who may be at low risk and not need the biopsy or additional costly tests such as newer biomarkers or prostate MRI,” they wrote.
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