Tpot and head and neck cancer: where are we now?

Cell proliferation measurements using bromodeoxyuridine administration to patients and flow cytometry to measure Tpot in head and neck cancer are discussed. Several hundred patients have now been assessed and the majority of studies suggest that this group of tumours represent a relatively fast proliferating site with a median Tpot of between 4 and 5 days. Despite the prevalence of fast proliferating tumours, the measurement has failed to make a consistent impact in being able to discriminate patients who do badly when treated by radiotherapy. Reasons for this include small numbers of patients in individual studies and difficulties inherent in the analysis of the complex flow cytometry profiles making accuracy and reproducibility of the measurement suspect. Larger, multi-centre studies, involving quality control, are still required to finally establish the clinical significance, or lack of, of the Tpot measurement.