Genetic testing in prostate cancer is increasing over time, data suggests

Recent data suggest that the volume of germline genetic tests ordered for patients with prostate cancer is increasing over time as the availability of targeted therapies continues to expand.¹

In Q2 of 2015, 21 patients underwent testing compared with 1509 patients in Q3 of 2020.

The findings were published in Urologic Oncology.

“The indications for hereditary germline testing in patients with prostate cancer are rapidly expanding,” said senior author Aditya Bagrodia, MD, FACS, an associate professor of urology at the University of California, San Diego Health, in correspondence with Urology Times^®. “It is critical that urologists understand when to order germline testing, are comfortable with actually ordering these tests, and integrate medical geneticists when appropriate.”

For the study, the investigators retrospectively assessed 17,256 patients with prostate cancer who underwent germline genetic testing (GGT). Of these, 14,400 patients were able to be linked with an ordering provider in an associated medical specialty and were thus included in the final analysis.

Among those included in the analysis, 8099 patients had tests ordered by medical oncology, 2824 had tests ordered by medical genetics, 915 had tests ordered by urology, 581 had tests ordered by primary care, and 438 had tests ordered by radiation oncology. Additionally, 1543 patients had tests ordered by other specialties, and 2856 patients were unassigned.

Data showed that the total number of patients with prostate cancer who underwent germline testing increased quarterly from 2015 to 2020. Specifically, in Q2 of 2015, 21 patients underwent testing compared with 1509 patients in Q3 of 2020.

The authors noted, “Tests ordered per quarter increased dramatically in Q2 of 2018 which coincided with the [National Comprehensive Cancer Network] (NCCN) guideline expansion, and a notable decrease was seen in Q1 2020.”

The NCCN guideline for prostate cancer early detection was expanded in 2018 to include patients with a strong family history, Ashkenazi Jewish ancestry, and “high risk, very high risk, regional, and metastatic prostate cancer,” according to the authors. Additionally, they note that the dip in 2020 coincides with the COVID-19 pandemic.

In line with this trend, the overall proportion of tests ordered by urologists increased over the same time period. In Q2 of 2015, 0% of urologists ordered germline tests vs 8.3% of urologists in Q3 and Q4 of 2020 (P < .001). The percentage of tests ordered by urologists generally increased year over year, with a slight dip in 2020. In total, no tests were ordered in 2015, which increased to 1.1% in 2016, 3.9% in 2017 (P = .04), 4.0% in 2018 (P = .021), 7.8% in 2019, and 7.6% in 2020. At the same time, the investigators noted a significant decrease in the percentage of tests ordered by other specialties (P < .001).

The authors wrote, “The percentage of germline tests ordered for patients with [prostate cancer] essentially doubled every 2 years between 2015–2020, rising from 0% in 2015 to over 7% in 2020. This significant increase is likely attributed to the expansion of guidelines and spotlight on GGT in the academic community over the last few years.”

Additional data showed that compared with medical genetics, medical oncology, and the composite ‘other’ categories, urology ordered a significantly higher percentage of tests for patients under the age of 70 (66% vs 51%-55%, P < .004) and those with a negative family history (25% vs 12%–20%, P = .012). However, urology was less likely to order tests for patients aged 70 to 79 (29.3%; P = .001) and 80 or older (5.3%; P = .005) compared to other specialties.

Additionally, urologists were more likely to order tests with large-sized panels compared with other specialties. Overall, 51% of tests order by urologists contained over 80 genes vs 29.4%-31.5% among those in other specialties (P < .001). Urologists also tended to order fewer 1-20 gene panels vs other specialties (P = .025).

“Our data indicates that urologists ordering GGT for [prostate cancer] are more likely to order larger panels, and for younger patients without a family history of cancer, suggesting that provider education may be useful to help urologists determine whether patients meet testing criteria, and consider a more [prostate cancer]-focused panel when appropriate,” the authors wrote.

Based on these findings, they also suggest a potential for future work.

They concluded, “Future directions of this research include comparing these trends to prostate cancer outcomes from databases over the same period to assess impact, correlating the respective GGT results to the trends described, and updating the data to include more recent years.”

Reference

1. Roberts JL, Wang LL, Rose B, et al. Germline genetic testing for prostate cancer: Ordering trends in the era of expanded hereditary cancer screening recommendations. Urol Oncol. 2024:S1078-1439(24)00690-2. doi:10.1016/j.urolonc.2024.10.010