Gene Expression Testing Varies Substantially by Region for Prostate Cancer

Michael Leapman, MD

Despite gene expression tests helping health care professionals make optimal treatment decisions, testing varies by region for men with prostate cancer and could be related to socioeconomic status and patterns of prostate cancer care, according to study findings published in JAMA Oncology.

Since genomic testing is now incorporated into major clinical practice guidelines, such as those from the National Comprehensive Cancer Network, investigators from Yale Cancer Center wanted to determine how often tissue-based genomic testing for prostate cancer was being adopted in the United States. Using insurance claims of more than 90,000 patients from Blue Cross Blue Shield Axis, the largest resource for health care claims, provider, and cost data, they identified trends among the patient population.

“Little was known about how genomic testing was used in routine clinical care,” said lead author Michael Leapman, MD, assistant professor of urology, clinical program leader of the Prostate and Urologic Cancers Program at Smilow Cancer Hospital and Yale Cancer Center. “We aimed to understand national patterns of uptake within regions in the United States. One of the interesting findings we uncovered was the extent of regional variation in the use of genomic testing.”

Investigators used group-based trajectory modeling to classify regions according to discrete trajectories of adoption of commercial, tissue-based genomic testing for prostate cancer. Hospital referral region (HRR)-level sociodemographic and healthcare contextual characteristics were compared using data previously gathered from Medicare beneficiaries across the trajectories.

The patient population included 92,418 men who received a prostate cancer diagnosis from July 1, 2012 through June 30, 2018. Median age at diagnosis was 60 years (range, 56-63). Study findings showed that genomic testing overall increased from 0.8% in July 2012 to June 2013 to 11.3% in July 2017 to June 2018. The highest rate of use was in Minot, North Dakota, which increased from less than 1.0% at baseline to 50% from July 2017 through June 2018, according to the study authors. No testing was performed in the latter study period in 17 regions.

In addition, investigators classified 5 regional trajectories of genomic testing adoption. At baseline, all groups had minimal utilization of genomic testing for patients with the disease. However, group 1 (lowest trajectory of adoption) increased to 4.0%. Usage in group 5 (highest trajectory of adoption) increased to 33.8%. Groups 2 through 4 had a modest increase in genomic testing (7.8%, 14.6%, and 17.3%, respectively). After examining geographic location, investigators found that 4 of 7 HRRs in group 5 were in Michigan. Other regions included Arkansas, Illinois, and North Dakota. In the lowest adoption, HRRs had no clear geographic relationship. 

“Some regions had minimal or no use of genomic testing, while others had high levels of use, implying that decisions to test are highly discretionary,” said Leapman. “In addition, there were groups of geographically unrelated regions that shared a similar pace of growth over time. These findings raise questions about shared factors that might promote rapid uptake of new cancer technologies.”

Compared with HRRs with the lowest rate of adoption, the highest rate of adoption HRRs had higher median income (group 1, $50 412.8 [$6,907.4]; vs group 2, $54 419.6 [$11 324.5]; vs group 3, $61 424.0 [$17 723.8]; vs group 4, $58 508.3 [$15 174.6]; vs group 5, $58 367.0 [$13 180.5]; P for trend = .005), education levels (group 1, 25.6% [4.8%]; vs group 2, 27.5% [7.3%]; vs group 3, 30.3% [9.1%]; vs group 4, 29.8% [8.2%]; vs group 5, 30.4% [11.4%]; P for trend = .03), and measures of prostate cancer care, including clinician density (No. [SD] of clinicians per 100 000: group 1, 2.5 [0.3]; vs group 2, 2.5 [0.5]; vs group 3, 2.6 [0.5]; vs group 4, 2.7 [0.7]; vs group 5, 2.6 [0.5]; P for trend = .04) and rates of prostate-specific antigen (PSA) screening (percentage [SD] of PSA testing among patients aged 68-74 years: group 1, 29.4% [11.8%]; vs group 2, 32.4% [11.2%]; vs group 3, 33.1% [12.7%]; vs group 4, 36.1% [9.7%]; vs group 5, 28.8% [11.8%]; P for trend = .05). 

“These findings suggest that similar regional conditions may underlie shared developmental trajectories in the use of new risk assessment technologies used in decision-making for cancer care,” the researchers wrote. “Given ongoing efforts and expenditures related to prognostic biomarkers across cancer care, our findings offer timely insights about how these tools have been applied in the real-world setting.”

Reference

1. Leapman MS, Wang R, Ma S, et al. Regional adoption of commercial gene expression testing for prostate cancer. JAMA Oncol. Accessed November 25, 2020. doi:10.1001/jamaoncol.2020.6086