Saliva Test Predicts Prostate Cancer Risk

A recent study published in the New England Journal of Medicine highlights the potential of a saliva test to assess genetic risk for prostate cancer, offering a less invasive alternative to traditional blood tests. Conducted by an international team from the Institute of Cancer Research in London, this innovative test analyzes 130 genetic variants to generate a polygenic risk score (PRS) that demonstrates superior predictive power for aggressive forms of prostate cancer compared to the commonly used PSA blood test.

The PSA test has faced criticism for its low specificity, which can lead to false-positive results in up to 75% of cases. This often results in the detection of indolent tumors that may not require treatment, leading to unnecessary follow-up procedures such as MRIs and biopsies. In contrast, the PRS test offers a more targeted approach.

As part of the Barcode-1 study, 6,393 men of European descent, aged 55 to 69, were recruited from general practices and underwent genetic testing. Those in the highest 10% of PRS scores were invited for further diagnostic procedures, including MRIs and prostate biopsies.

The results revealed that 40% of men in the high-risk group had prostate cancer, a significantly higher detection rate compared to the PSA test, which only identifies cancer in about 25% of cases with elevated levels. Furthermore, the PRS test was particularly effective at identifying aggressive tumors, with a 55.1% detection rate, compared to just 35.5% for PSA-based diagnoses.

This genetic testing approach allows for the early identification of men at high genetic risk, enabling more informed decisions regarding further diagnostic evaluations. Additionally, it could spare men with low risk from unnecessary invasive procedures.

The study suggests that the PRS test should be integrated with existing diagnostic methods to optimize the balance between the benefits and risks associated with cancer screening. While the current study focuses on men of European ancestry, efforts are underway to develop versions of the test for men of African and Asian descent.

The underlying genetic variations, known as single nucleotide polymorphisms (SNPs), are individually associated with minimal prostate cancer risk; however, their cumulative effects are clinically significant. Although the functional implications of many SNPs remain unclear, researchers speculate that certain combinations may correlate with increased tumor growth or proliferation tendencies. The PRS thus represents a stable, lifelong risk factor that could theoretically be assessed early in life.

This research underscores the potential of genetic testing as a cost-effective, easily administered, and more precise tool for cancer detection. Further studies are necessary to evaluate long-term outcomes and the clinical advantages of widespread implementation.