In this JCO Precision Oncology Article Insights episode, Miki Horiguchi summarizes two articles: “Germline Susceptibility to Renal Cell Carcinoma and Implications for Genetic Screening,” by Dr. Kate I. Glennon et al. published on August 01, 2024, and
"Incidental Pathogenic Variants in Renal Cell and Urothelial Carcinoma: Is It Time for Universal Screening?” by Dr. Salvador Jaime-Casas, et al. published on August 01, 2024.

TRANSCRIPT

Miki Horiguchi: Hello and welcome to JCO Precision Oncology Article Insights. I'm your host Miki Horiguchi, an ASCO Journal's Editorial Fellow. Today, I'll be providing summaries of the article titled, "Germline Susceptibility to Renal Cell Carcinoma and Implications for Genetic Screening,” by Dr. Kate Glennon and colleagues. In the accompanying editorial titled, “Incidental Pathogenic Variants in Renal Cell and Urothelial Carcinoma: Is It Time for Universal Screening?” by Dr. Salvador Jaime-Casas and colleagues.

Renal cell carcinoma (RCC) exhibits distinct clinical characteristics across its histological subtypes. Clear cell RCC accounts for approximately 75% of cases while the remaining non-clear cell RCC encompasses a diverse group of histology. Although a family history has been known to double the risk for RCC, genetic susceptibility, particularly across different histological subtypes and defined operations, has not been investigated well.

Dr. Glennon and colleagues sought to identify risk genes for RCC within the Canadian population and investigate their clinical significance in comparison to cancer-free control populations. The authors conducted targeted sequencing of 19 RCC related genes and 27 cancer predisposition genes for 960 RCC patients in Canada. DNA samples were collected through the Ontario Tumour Bank between 2005 and 2019. For comparisons across histological subtypes, the cohort was divided into 759 patients with clear cell RCC and 201 patients with non-clear cell RCC, including all histological subtypes other than clear cell RCC. Non-cancer control data were obtained from a publicly available database which included over 118,000 cases from the European population. A total of 39 different germline pathogenic variants were identified in 56 patients representing 5.8% of the Canadian cohort. There was no significant difference in the overall number of germline pathogenic variants between the two groups. The most commonly identified germline pathogenic mutations were CHEK2, ATM/BRCA2 and MITF in the clear cell RCC group, and FH and CHEK2 in the non-clear cell RCC group.

Compared to the non cancer control data, germline pathogenic variants in CHEK2 and ATM were significantly associated with an increased risk of developing clear cell RCC, while those in FH were significantly associated with non clear cell RCC. According to the bivariate association analysis between the presence of germline pathogenic variants and clinical characteristics, patients with metastatic RCC were strongly associated with pathogenic variants in BRCA1, BRCA2, and ATM. No other significant associations were observed.

The authors then evaluated variations in germline pathogenic variants among RCC patients across the world using similar studies conducted in Canada, Japan, the United Kingdom, and the United States. Specifically, they compared the gene burden for significantly mutated genes in each of the cohorts against all other cohorts combined. Compared to the other cohorts, RCC patients from Japan were enriched for pathogenic variants in TP53 and depleted for pathogenic variants in CHEK2. The United States cohorts showed higher frequencies of patients with pathogenic variants in BAP1 and FH genes compared to other cohorts. In contrast, RCC patients from Canada and the United Kingdom were not enriched for any specific genes when compared with the other cohorts.

After characterizing germline susceptibility to RCC, the authors evaluated how many of the RCC patients in the Canadian cohort did not meet existing referral criteria for genetic screening based on current clinical guidelines, aiming to help refine these guidelines. Among the 56 RCC patients with identified germline pathogenic variants in the Canadian cohort, 73% did not meet the referral criteria for genetic screening under current Canadian guidelines. The authors also applied the UK guidelines and the US American College of Medical Genetics guidelines to the same 56 RCC patients. Under these criteria, 80% and 64%, respectively, were not eligible for genetic screening. In an exploratory analysis, the authors examine the impact of raising the Asia onset threshold from less than 45 years to less than 50 years. This revision captured an additional five patients with pathogenic variants. In addition to more inclusive genetic screening guidelines, the study results suggest that expanding the current list of genes to include additional relevant genes such as BRCA1, BRCA2, CHEK2 and ATM could help identify more RCC patients who are affected by rare germline pathogenic variants in Canada. The authors concluded that these revisions would enable the identification of a higher number of at-risk patients and improve the management of RCC patients.

In the associated editorial accompanying this research article, Dr. Salvador Jaime-Casas and colleagues emphasized that the findings from Dr. Glennon and colleagues’ study are particularly worrisome as most RCC patients with incidental pathogenic variants are not being referred for genetic screening. Building on results from previous studies, the authors suggested the need to revisit and update the current screening guidelines for RCC patients. The authors also highlighted findings from other studies showing the prevalence of pathogenic variants in CHECK2, BRCA1, and BRCA2 at up to 6% in RCC patients and 11% in upper tract urothelial carcinoma patients. They noted that these rates are comparable to those of ovarian cancer and pancreatic cancer, which already have universal screening guidelines.

The authors also discuss some challenges. While the prevalence of pathogenic variants is crucial for evaluating the impact of germline genetic testing, it's only one factor in devising screening guidelines for RCC and urothelial carcinoma. They emphasize the need for robust clinical trials to evaluate therapeutics targeting these pathways, as well as the importance of characterizing incidental pathogenic variants to guide patient selection for these trials.

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