A low-grade prostate tumor is not necessarily low-risk, new research suggests.
Biopsy results showing low-grade prostate cancers can sometimes lead to underestimation of disease risk and omission of surgery or radiation in patients who might benefit from such treatments, researchers warned in JAMA Oncology.
Among roughly 117,000 men in their study with prostate biopsy results indicating a Grade Group 1 tumor – the slowest-growing kind - one in six had intermediate- or high-risk cancer when other factors such as prostate-specific antigen levels in the blood and tumor sizes were also considered, according to the report.
Such higher risk cancers are often treated with radiation therapy or removal of the prostate, the researchers noted.
"We don't want to miss aggressive cancers that initially present as Grade Group 1 on biopsy," study coauthor Dr. Bashir Al Hussein of Weill Cornell Medicine said in a statement. "Such underestimation of risk could lead to undertreatment and poor outcomes."
Current guidelines that advise regular monitoring – rather than treatment – for men with low-grade prostate tumors were based on studies that examined entire prostate glands after removal from patients.
Biopsies test only small areas of the prostate, so they can miss more advanced or aggressive cancer cells, providing an incomplete picture, the researchers said.
Some cancer experts have been suggesting recently that Grade Group 1 tumors are so slow-growing that they shouldn't even be considered malignant. The new study results could help inform those discussions, the researchers said.
"There is a misunderstanding that low grade and low risk are the same," study coauthor Dr. Jonathan Shoag of Case Western Reserve University said in a statement. "Here, we show clearly that they are not."
