Slebos, Robbert J.C.

6016 Background: A germline mutation in let-7 complementary site 6 (LCS6) within the KRAS 3'-untranslated region (rs61764370, the KRAS-variant: TG/GG) is known to associate with poor outcome and drug resistance in various cancers compared to the wild type allele (TT). We examine the prognostic significance of the KRAS-variant in recurrent/metastatic (R/M) head and neck squamous cell carcinoma (HNSCC). Methods: The KRAS-variant was determined in 116 tumor DNA samples from HNSCC patients enrolled in 3 clinical trials and a tissue collection study using a previously validated PCR-based assay. Results: KRAS-variant status could be determined in 108/116 (93%) samples and an allele frequency of TG/GG was 28.7%. These results were correlated with patient demographics, p16/human papillomavirus (HPV) status and clinical outcome. There was no association between p16/HPV status and the KRAS-variant status (Fisher’s exact test, p=1.0). The KRAS-variant was associated with poor progression-free survival in patients treated with cisplatin+/-cetuximab (log-rank p=0.002) but this association was not observed in docetaxel/bortezomib treated patients (log-rank p=0.89). Conclusions: KRAS-variant is a potentially promising biomarker of poor prognosis and a predictive biomarker of cisplatin resistance in R/M HNSCC. Prospective validation is warranted. Clinical trial information: NCT00003809.