Survival of the Hmong population diagnosed with colon and rectal cancers in the United States

BACKGROUND

The Hmong population constitutes an independent ethnic group historically dispersed throughout Southeast Asia; fallout from the Vietnam War led to their forced migration to the United States as refugees. This study seeks to investigate characteristics of the Hmong population diagnosed with in colorectal cancer (CRC) as well as survival within this population.

METHODS

Cases of colon and rectal adenocarcinoma diagnosed between 2004 and 2017 were identified from the National Cancer Database (NCDB). Summary statistics of demographic, clinical, socioeconomic, and treatment variables were generated with emphasis on age and stage at the time of diagnosis. Cox-proportional hazard models were constructed for survival analysis.

RESULTS

Of 881,243 total CRC cases within the NCDB, 120 were classified as Hmong. The average age of Hmong individuals at diagnosis was 58.9 years compared 68.7 years for Non-Hispanic White (NHW) individuals (p < 0.01). The distribution of analytic stage differed between the Hmong population and the reference NHW population, with 61.8% of Hmong individuals compared to 45.8% of NHW individuals with known stage being diagnosed at stage III or IV CRC compared to 0, I, or II (p = 0.001). However, there was no difference in OS when adjusting for potential confounders (HR 1.00 [0.77-1.33]; p = 0.998).

CONCLUSIONS

Hmong individuals are nearly a decade younger at the time of diagnosis of CRC compared to the NHW individuals. However, these data do not suggest an association between Hmong ethnicity and overall survival, when compared to the NHW population.

The Identification of Novel CYP2D6 Variants in US Hmong: Results From Genome Sequencing and Clinical Genotyping

Objective: Hmong individuals represent a unique East Asian subpopulation in whom limited information concerning pharmacogenetic variation exists. The objectives of this study were to comprehensively characterize the highly polymorphic CYP2D6 gene in Hmong, estimate allele and phenotype frequencies and to compare results between two testing platforms. Methods: DNA from 48 self-identified Hmong participants were sequenced using a targeted next-generation sequencing (NGS) panel. Star allele calls were made using Astrolabe, manual inspection of NGS variant calls and confirmatory Sanger sequencing. Structural variation was determined by long-range (XL)-PCR and digital droplet PCR (ddPCR). The consensus diplotypes were subsequently translated into phenotype utilizing the activity score system. Clinical grade pharmacogenetic testing was obtained for 12 of the 48 samples enabling an assessment of concordance between the consensus calls and those determined by clinical testing platforms. Results: A total of 13 CYP2D6 alleles were identified. The most common alleles were CYP2D6*10 and its structural arrangements (37.5%, 36/96) and the *5 gene deletion (13.5%, 13/96). Three novel suballeles (*10.007, *36.004, and *75.002) were also identified. Phenotype frequencies were as follows: ultrarapid metabolizers (4.2%, 2/48), normal metabolizers (41.7%, 20/48) and intermediate metabolizers (52.1%, 25/48); none of the 48 participants were predicted to be poor metabolizers. Concordance of diplotype and phenotype calls between the consensus and clinical testing were 66.7 and 50%, respectively. Conclusion: Our study to explore CYP2D6 genotypes in the Hmong population suggests that this subpopulation is unique regarding CYP2D6 allelic variants; also, a higher portion of Hmong participants (50%) are predicted to have an intermediate metabolizer phenotype for CYP2D6 compared to other East Asians which range between 27 and 44%. Results from different testing methods varied considerably. These preliminary findings underscore the importance of thoroughly interrogating unique subpopulations to accurately predict a patient's CYP2D6 metabolizer status.

Redefining precision cancer prevention to promote health equity

Precision cancer prevention as it is currently envisioned is a targeted, molecular-based approach to intercept carcinogenesis before cancer develops or before it becomes untreatable. Unfortunately, due to systemic biases, current precision cancer prevention interventions might not be effective in all populations, especially in minoritized communities. In addition, not all cancer risk is attributable to genetic or even biological factors, but includes social determinants of health (SDH). Here, we propose a broader framework for precision cancer prevention, anchored in optimizing the benefits to harms for all people. We propose that precision cancer prevention considers not only what is being delivered, but also for whom, where, and how, with a goal of achieving cancer prevention health equity.

Potential Clinical Relevance of Differences in Allele Frequencies Found within Very Important Pharmacogenes between Hmong and East Asian Populations

OBJECTIVES

Implementing pharmacogenetics for very important pharmacogenes (VIPs) holds the promise of improving clinical outcomes through optimal medication selection and dosing. However, significant differences in the frequency of actionable variants in VIPs may exist within subpopulations of a given ancestral group. Furthermore, these differences can potentially impact drug selection and dosing. The purpose of this study was to ascertain allele frequencies for VIPs and to predict medication requirements using Clinical Pharmacogenetics Implementation Consortium (CPIC) guidelines in Hmong and compare with published data for East Asians.

METHODS

Using a community-based participatory action research approach, DNA collected from 194 Hmong adults living in the United States was analyzed for 22 genetic variants within eight VIPs (CYP2C9, CYP2C19, CYP4F2, DPYD, G6PD, SLCO1B1, TPMT, VKORC1). Allele frequencies for VIPs and predicted medication requirements using CPIC guidelines were compared between Hmong participants and East Asians.

RESULTS

Significant differences in allele frequencies between the Hmong and East Asians were found for 23% (5/22) of the CPIC-actionable variants tested. Allele frequencies for VIPs in Hmong versus East Asians were 16.6% versus 3.4% in CYP2C9*3A, 42.2% versus 29.0% for CYP2C19*2, 0.3% versus 8.3% in CYP2C19*3, 6.5% versus 22.1% in CYP4F2*3, and 3.6% versus 0.1% in SLCO1B1*5, respectively. These differences significantly influenced predicted medication usage recommendations in warfarin, simvastatin, and phenytoin between Hmong and East Asians.

CONCLUSIONS

Important differences in allele frequencies for key genetic variants influencing selection of medications and dosages were found between the Hmong and East Asians. The magnitude and nature of these differences can be expected to result in different medication recommendations for the Hmong relative to East Asians.