This significance suggests that this patient sample was representative for the patient population with head and neck cancer. In a multivariate analysis with respect to the risk of loco-regional tumour failure, only disease stage yielded independent prognostic significance. Neither tumour cell SF2, overall SF2, nor plating efficiency predicted loco-regional tumour control probability. Advanced stage, lymph node involvement and tumour size correlated statistically significantly with poor loco-regional control. Among the 38 patients grouped in loco-regional failures and patients with loco-regional control, respectively, sex, age, total radiation dose, overall treatment time and tumour grade were equally distributed. In general, the measures of tumour radiosensitivity were independent of patient sex and age, T- and N-category, disease stage, tumour size and plating efficiency. Using weighted linear regression, it was demonstrated that tumour cell SF2 and overall SF2 were two independent measures of tumour radiosensitivity. By collecting the obtained colonies on a preparation slide using a colony-filter technique, and with immunocytochemical staining, it was possible to measure the surviving fraction of tumour cells selectively as tumour cell SF2.Įxperimentally, a broad inter-tumour variation was found for both tumour cell SF2 and overall SF2. Directly from this assay and with no respect to cell type, overall SF2 was assessed. Pre-treatment biopsies were disaggregated to form a single-cell suspension and cells were cultured in the modified Courtenay-Mills soft agar clonogenic assay. Thirty-eight patients with squamous cell carcinoma of the head and neck were treated with curative radiotherapy alone.
In the current study, cellular in vitro radiosensitivity was estimated as the fraction of surviving cells after a radiation dose of 2 Gy (SF2) and related to clinical outcome after curative radiotherapy. Variation in tumour cell radiosensitivity is believed to be an important underlying factor. Clinically, it is recognized that individual tumours respond differently to radiation treatment.