A63
Novel epigenetic biomarkers in the diagnosis of minimal residual disease in head and neck cancer (HNSCC)
Andrew Hobkirk, Richard Shaw, Janet Risk, Lakis Liloglou
University of Liverpool, Liverpool, UK
Background
Gene promoter methylation plays a key role in HNSCC carcinogenesis and can be utilised as a biomarker for minimal residual disease following surgery. A positive molecular margin is defined as sub-microscopic tumour (i.e. beyond that seen histopathologically) which may account for local tumour recurrence. Molecular tests have proved sensitive and specific at detecting minimal residual disease and may better direct surgery and adjuvant therapy so reducing morbidity and mortality.
Method
Cohort: 50 consecutive patients with a new diagnosis of oral squamous cell carcinoma (T2-4) treated with primary surgery. After removal of tumour, 10x2mm3 specimens from beyond the deep (x5) and mucosal (x5) surgical margin were coded and stored at -85C. DNA was extracted (DNeasy Blood & Tissue Kit, Qiagen), quantified with spectrophotometry (Nanodrop, Thermo Fisher Scientific) and bilsulphite converted (EZ DNA Methylation Kit, Zymo Research). Quantitative Methylation Specific Real Time PCR was carried out for P16, TMEFF2, CYGB and MGMT.
Results
Of the 50 patients 13 (26%) of tumours were informative for p16 promoter hypermethylation and 11 (22%) for TMEFF2 promoter hypermethylation. These cases were almost exclusive so informativity was 46% overall. 100 margin samples from 10 patients were evaluated (to date) for both genes. Of the 3 p16 informative patients, 2 had positive molecular mucosal margins and one deep. Of the 3 TMEFF2 informative patients, all 3 had some positive mucosal margins and one also a positive deep margin. Of these 10 patients 4 (40%) have developed local recurrence despite non-involved resection margins on histopathological assessment. Of the 4 recurrences, 3 (75%) had positive molecular margins.
Conclusion
The data show that RT-MSP assays can identify molecular evidence in clear tissues using routine histopathology in patients who ultimately develop recurrences.
