Clinical utility of serial analysis of circulating tumour cells for detection of minimal residual disease of metastatic nasopharyngeal carcinoma.

BACKGROUND: Nasopharyngeal carcinoma (NPC) is an important cancer in Hong Kong. We aim to utilise liquid biopsies for serial monitoring of disseminated NPC in patients to compare with PET-CT imaging in detection of minimal residual disease. METHOD: Prospective serial monitoring of liquid biopsies was performed for 21 metastatic patients. Circulating tumour cell (CTC) enrichment and characterisation was performed using a sized-based microfluidics CTC chip, enumerating by immunofluorescence staining, and using target-capture sequencing to determine blood mutation load. PET-CT scans were used to monitor NPC patients throughout their treatment according to EORTC guidelines. RESULTS: The longitudinal molecular analysis of CTCs by enumeration or NGS mutational profiling findings provide supplementary information to the plasma EBV assay for disease progression for good responders. Strikingly, post-treatment CTC findings detected positive findings in 75% (6/8) of metastatic NPC patients showing complete response by imaging, thereby demonstrating more sensitive CTC detection of minimal residual disease. Positive baseline, post-treatment CTC, and longitudinal change of CTCs significantly associated with poorer progression-free survival by the Kaplan-Meier analysis. CONCLUSIONS: We show the potential usefulness of application of serial analysis in metastatic NPC of liquid biopsy CTCs, as a novel more sensitive biomarker for minimal residual disease, when compared with imaging.

Leukocyte telomere length associates with nasopharyngeal carcinoma risk and survival in Hong Kong Chinese.

Telomere shortening occurs as an early event in tumorigenesis. The TERT-CLPTM1L locus associates with nasopharyngeal carcinoma (NPC) risk. It remains unknown if leukocyte telomere length (LTL) associates with NPC risk and survival. The relative LTL (rLTL) was measured by quantitative-PCR in 2,996 individuals comprised of 1,284 NPC cases and 1712 matched controls. The odds ratio (OR) and 95% confidence intervals (CI) were calculated by logistic regression. The hazard ratio (HR) and 95% CI were calculated by Cox regression for survival analysis with rLTL and other clinical parameters in 1,243 NPC with a minimum follow-up period of 25 months. NPC patients had significantly shorter telomere length than controls. Shorter rLTL significantly associated with increased NPC risk, when the individuals were dichotomized into long and short telomeres based on median-split rLTL in the control group (OR = 2.317; 95% CI = 1.989-2.700, p = 4.10 × 10-27 ). We observed a significant dose-response association (ptrend  = 3.26 × 10-34 ) between rLTL and NPC risk with OR being 3.555 (95% CI = 2.853-4.429) for the individuals in the first quartile (shortest) compared with normal individuals in the fourth quartile (longest). A multivariate Cox regression analysis adjusted by age demonstrated an independent effect of rLTL on NPC survival for late-stage NPC patients, when the individuals were categorized into suboptimal rLTL versus the medium rLTL based on a threshold set from normal (HR = 1.471, 95% CI = 1.056-2.048, p = 0.022). Shorter blood telomeres may be markers for higher susceptibility for NPC risk. Suboptimal rLTL may be a poor prognostic factor for advanced NPC patients, as it associates independently with poor survival.

Clinical Outcome-Related Mutational Signatures Identified by Integrative Genomic Analysis in Nasopharyngeal Carcinoma.

PURPOSE: Investigation of biological mechanisms underlying genetic alterations in cancer can assist the understanding of etiology and identify the potential prognostic biomarkers. EXPERIMENTAL DESIGN: We performed an integrative genomic analysis for a total of 731 nasopharyngeal carcinoma cases from five independent nasopharyngeal carcinoma cohorts to identify the genetic events associated with clinical outcomes. RESULTS: In addition to the known mutational signatures associated with aging, APOBEC and mismatch repair (MMR), a new signature for homologous recombination deficiency (BRCAness) was discovered in 64 of 216 (29.6%) cases in the discovery set including three cohorts. This signature appeared more frequently in the recurrent and metastatic tumors and significantly correlated with shorter overall survival (OS) in the primary tumors. Independent prognostic value of MMR and BRCAness signatures was revealed by multivariable Cox analysis after adjustment for clinical parameters and stratification by studies. The cases with both signatures had much worse clinical outcome than those without these signatures [hazard ratio (HR), 12.4; P = 0.002]. This correlation was confirmed in the validation set (HR, 8.9; P = 0.003). The BRCAness signature is highly associated with BRCA2 pathogenic germline or somatic alterations (7.8% vs. 0%; P = 0.002). Targeted sequencing results from a prospective nasopharyngeal carcinoma cohort (N = 402) showed that the cases carrying BRCA2 germline rare variants are more likely to have poor OS and progression-free survival. CONCLUSIONS: Our study highlights importance of defects of DNA repair machinery in nasopharyngeal carcinoma pathogenesis and their prognostic values for clinical implications. These signatures will be useful for patient stratification to evaluate conventional and new treatment for precision medicine in nasopharyngeal carcinoma.

Nasopharyngeal carcinoma MHC region deep sequencing identifies HLA and novel non-HLA TRIM31 and TRIM39 loci.

Despite pronounced associations of major histocompatibility complex (MHC) regions with nasopharyngeal carcinoma (NPC), causal variants underlying NPC pathogenesis remain elusive. Our large-scale comprehensive MHC region deep sequencing study of 5689 Hong Kong Chinese identifies eight independent NPC-associated signals and provides mechanistic insight for disrupted transcription factor binding, altering target gene transcription. Two novel protective variants, rs2517664 (Trs2517664 = 4.6%, P = 6.38 × 10-21) and rs117495548 (Grs117495548 = 3.0%, P = 4.53 × 10-13), map near TRIM31 and TRIM39/TRIM39-RPP21; multiple independent protective signals map near HLA-B including a previously unreported variant, rs2523589 (P = 1.77 × 10-36). The rare HLA-B*07:05 allele (OR < 0.015, P = 5.83 × 10-21) is absent in NPC, but present in controls. The most prevalent haplotype lacks seven independent protective alleles (OR = 1.56) and the one with additional Asian-specific susceptibility rs9391681 allele (OR = 2.66) significantly increased NPC risk. Importantly, this study provides new evidence implicating two non-human leukocyte antigen (HLA) genes, E3 ubiquitin ligases, TRIM31 and TRIM39, impacting innate immune responses, with NPC risk reduction, independent of classical HLA class I/II alleles.