Is there a role for [F]-FMISO PET to guide dose adaptive radiotherapy in head and neck cancer? A review of the literature.

Purpose: Hypoxia is a major cause of radioresistance in head and neck cancer (HNC), resulting in treatment failure and disease recurrence. F-fluoromisonidazole [F]FMISO PET has been proposed as a means of localising intratumoural hypoxia in HNC so that radiotherapy can be specifically escalated in hypoxic regions. This concept may not be deliverable in routine clinical practice, however, given that [F]FMISO PET is costly, time consuming and difficult to access. The aim of this review was to summarise clinical studies involving [F]FMISO PET to ascertain whether it can be used to guide radiotherapy treatment in HNC.

Methods: A comprehensive literature search was conducted on PubMed and Web of Science databases. Studies investigating [F]FMISO PET in newly diagnosed HNC patients were considered eligible for review.

Results: We found the following important results from our literature review: 1)Studies have focussed on comparing [F]FMISO PET to other hypoxia biomarkers, but currently there is no evidence of a strong correlation between [F]FMISO and these biomarkers.2)The results of [F]FMISO PET imaging are not necessarily repeatable, and the location of uptake may vary during treatment.3)Tumour recurrences do not always occur within the pretreatment hypoxic volume on [F]FMISO PET.4)Dose modification studies using [F]FMISO PET are in a pilot phase and so far, none have demonstrated the efficacy of radiotherapy dose painting according to [F]FMISO uptake on PET.

Conclusions: Our results suggest it is unlikely [F]FMISO PET will be suitable for radiotherapy dose adaptation in HNC in a routine clinical setting. Part of the problem is that hypoxia is a dynamic phenomenon, and thus difficult to delineate on a single scan. Currently, it is anticipated that [F]FMISO PET will remain useful within the research setting only.