A 45-year-old man presented with a left-sided posterior triangle neck node and a history of sore throats for a year. At the time of presentation he had no other symptoms. An examination under anaesthetic was undertaken and revealed no abnormality of the larynx or pharynx but a suspicious area was seen in the nasopharynx. Biopsy of this region, however, was normal. Histology of the nodes dissected from the left side of the neck revealed anaplastic carcinoma and the appearances were in keeping with a primary from the nasopharynx or bronchus. Tonsillar biopsy was normal. On clinical judgment the nasopharynx was thought to be the most likely primary site and so the patient was treated with radical radiotherapy to the neck and nasopharynx. The neck was treated with an anterior beam of MV photons from a linear accelerator with midline shielding (2 cm wide, 6 cm thick) to redbce the dose to the spinal cord (Ho, 1978).

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Dr Bretland (1988b) has omitted an important factor from his calculations of the cost of oral cholecystography—that of the harm done by ionizing radiation. This has been calculated at £5–10 000 man-Sv−1 (Russell & Webb, 1987). Since this estimate was made, our perception of fatal cancer induction has at least doubled (International Commission on Radiological Protection (ICRP), 1987) so it is reasonable to take £10 000 as the value of avoiding a man-Sv.