THE IN-VITRO RADIOSENSITIVITY OF HUMAN HEAD AND NECK CANCERS

A study was made of the intrinsic radiosensitivity of 140 biopsy and s urgical specimens of malignant head and neck tumours of different hist ologies. Using a soft-agar clonogenic assay, the material was assessed for the ability to grow in culture (colony-forming efficiency; CFE) a nd inherent tumour radiosensitivity (surviving fraction at 2 Gy, SF2). The success rate for obtaining growth was 74% (104/140) with a mean C FE of 0.093% (median 0.031) and a range of 0.002-1.3%. SF2 was obtaine d for 88 of 140 specimens, representing a success rate of 63% with a m ean SF2 of 0.48 (median 0.43) and a range of 0.10-1.00. There were no significant differences in radiosensitivity between different sites oi the head and neck region. There were no significant relationships bet ween SF2 and disease stage, nodal status, tumour grade, patient age, p rimary tumour growth pattern and CFE, The results were compared with t hose for other tumour types previously analysed with the same assay. T he distribution of the SF2 values for the head and neck tumours was si milar to that for 145 cervix carcinomas and there was no significant d ifference in mean radiosensitivity between the two tumour types, Also, there was no significant difference in radiosensitivity between head and neck tumours and either breast or colorectal cancers. However, a g roup of eight lymphomas was significantly more radiosensitive. These r esults confirm the feasibility of carrying out radiosensitivity measur ements using a soft-agar clonogenic assay on head and neck tumours. In addition, the work has shown that radiosensitivity is independent of many clinical parameters and that the mean value is similar to that re ported for cervix carcinomas.