Use of circulating tumour DNA in nasopharyngeal carcinoma to detect minimal residual disease

Circulating tumour DNA (ctDNA) is defined as short DNA sequences shed by tumour cells into the systemic circulation. A promising use of ctDNA includes the detection of minimal residual disease (MRD) and is currently being studied in multiple types of solid tumours. Literature for the use of individualised ctDNA in nasopharyngeal carcinoma (NPC) is not available, although circulating Epstein-Barr virus DNA level is validated as a prognostic factor. We present a man in his 40s diagnosed with stage IV NPC who was started on chemotherapy with cis-platinum and gemcitabine. Serial monitoring of ctDNA completed to aid in detecting MRD after treatment demonstrated initial up-trending values correlating with subsequent imaging findings showing progression. Reinitiation of a different chemotherapy regimen significantly improved the ctDNA level, with corresponding imaging exhibiting a similar response. This case provides insight into the potential use of ctDNA in NPC and the benefit of serial ctDNA monitoring during treatment.