Use of Genomic Testing for Prostate Cancer Still Highly Variable Across the U.S.

The adoption of commercially available, tissue-based genomic testing (TBGT) in men diagnosed with prostate cancer has been highly variable across different regions in the United States and may reflect the degree to which patients have access to health care and resources, a dynamic cohort study found.

In a group of 92,418 patients with prostate cancer, there was minimal use of genomic testing (0.8%) of patients between July 2012 and June 2013, Michael Leapman, MD, Yale School of Medicine in New Haven, Connecticut, and colleagues reported in JAMA Oncology. However, the use of TBGT increased to 11.3% of patients diagnosed with the same cancer from July 2017 through to June 2018, they added.

On the other hand, when analyzed at the hospital referral region (HRR) level, there was substantial regional variation in the use of genomic testing, with many HRRs showing either minimal or no use of genomic testing even at the most recent time points analyzed. Indeed, there was over an 8-fold difference in the use of genomic testing between regions that were high adopters of TBGT and those classified as low adopters, Leapman and colleagues pointed out. And, in those clusters of HRRs where TBGT was more rapidly adopted, levels of education, household income and measures of prostate cancer care, including clinician density and rates of prostatic-specific antigen (PSA) testing, were all substantially higher compared to clusters of HRRs where genomic testing was less frequently used.

“Tissue-based multigene panel (genomic) tests… have been particularly promising for the management of prostate cancer, where the aggressiveness of the disease varies considerably among men with localized cancers,” the authors noted. “[We found that] regional variation in the use of new prognostic genomic tests for prostate cancer was associated with underlying differences in resources and prostate cancer services.”

The primary data source for the current study came from Blue Cross Blue Shield, Axis administrative claims, the largest source of commercial insurance claims in the U.S.

Patients between the ages of 40 and 89 years who were diagnosed with prostate cancer between July 1, 2012 and June 30, 2018 were included in the analysis. The median age at the time of diagnoses was 60 years (Interquartile range [IQR], 56-63 years). In total, there were 217 evaluable HRRs where the use of genomic testing was analyzed.

All regions reported minimal use of genomic testing at baseline. However, in regions where adoption of genomic testing was highest, use increased to include over one-third of prostate cancer patients by study endpoint. The highest rate of utilization was seen in Minot, North Dakota, where it increased from less than 1% at baseline to 50% in prostate cancer patients diagnosed from July 2017 to June 2018.

“In contrast, there were 17 regions in which no testing was performed [even] in the latter study period,” Leapman and colleagues reported.

Regions where genomic testing was used the most also had a higher percentage of patients with college education; higher median household income; higher urologist clinician density, and a higher percentage of PSA testing among patients between 68 and 74 years of age.

“[O]ur findings are consistent with other studies that have identified sociodemographic variation at the regional level in the adoption of diagnostic technologies for other cancers, including digital breast tomography,” the authors observed. “[T]his work can catalyze greater interest in studying not only the effectiveness of these tests, but the equity of their dissemination.”

Clinical Practice Guidelines

As the authors pointed out, recommendations for genomic testing have been incorporated into several major clinical practice guidelines and are covered by most major insurance carriers, including Medicare.

However, as noted by editorialists Daniel Lin, MD, University of Washington, Seattle, Washington, and Peter Nelson, MD, Fred Hutchinson Cancer Research Center, Seattle, Washington, despite their promise and availability, “TGBTs have not been prospectively validated or shown to improve long-term outcomes and, to date, none are recommended for routine use in standard-of-care guidelines.”

The fact that the highest rates of genomic testing as reported by Leapman et al were seen in regions with higher educational levels, higher median household incomes and higher rates of prostate cancer screening suggests that these are the regions where men have increased access to health care and resources, as the editorialists also pointed out.

“The appropriateness of TGBT utilization is a central issue to this report, and ascertainment of appropriate use requires linkage to clinical data, which was unfortunately not available,” Lin and Nelson observed. The fact that the highest rates of TGBT use occurred in a city with a population of under 50,000 in 2018 suggests that reasons for this high rate of use likely go beyond reported socioeconomic factors and that “relationships with industry” as the authors themselves referred to may well have contributed to high genomic testing rates, the editorialists noted.

Furthermore, all currently available TGBTs were developed in patients who had already undergone treatment for prostate cancer and who were therefore at much higher risk than patients considered candidates for active surveillance. The editorialists pointed out that application of these same tests to lower-risk patients is thus limited or has not yet been studied by companies who develop these assays.

“[M]ultiple guidelines and consensus statements have concluded that the effectiveness of [these] tests is not established; the tests should be used in combination with available clinical variables in situations that will affect clinical management; and [that] they should not be used routinely,” Lin and Nelson emphasized. “TGBTs are only 1 part of multiparameter models that incorporate other clinicopathologic variables that are also independently associated with outcomes.”

1. Utilization rates of genomic testing in men with prostate cancer were still highly variable across different regions of the U.S. as recently as 2018.

2. Regions with the highest rates of tissue-based genomic testing had higher levels of education, higher household income, and higher measures of prostate cancer care, suggesting men in these regions had greater access to health care and resources.

Pam Harrison, Contributing Writer, BreakingMED™

Cat ID: 25

Topic ID: 78,25,730,25,192,151,925