CANCER patients may die while queueing up for treatment due to a severe shortage of therapeutic radiographers, a medical expert has warned. A Hospital Authority paper obtained by the Sunday Morning Post showed that by July, public hospitals would lack 50 specialist radiographers or 35 per cent of the level required to maintain proper service. Professor Constantine Metreweli, head of the Chinese University's Department of Diagnostic Radiology and Organ Imaging, said: ''This means we will not have enough people to operate the cancer treatment machine. Patients are going to die while waiting.'' The paper showed a staff shortage in the year ahead in anaesthesiology, pathology, psychiatry, nursing, and diagnostic radiology. It recommended overseas recruitment which the HA said would cost more. Also, manpower projections for senior medical officers in radio-diagnosis showed ''a large number of vacancies'' would appear. The paper says although the shortage of nurses has eased somewhat in the year ending March 1993, recruitment of overseas nurses should remain an option because of the planned commissioning of additional beds and other new services. It suggested the recruitment be conducted for a period of one year, after which the need should be reviewed. But Professor Metreweli last night warned of a drop in standards. ''I am getting a lot of letters from people overseas whose standard is questionable,'' he said. The Hospital Authority estimates a shortfall of 154 registered nurses for 1993-94 based on a total of 1,340 new recruits, against an estimated loss of 1,120 nurses and the need for 374 additional nurses to man new services and extra beds. Overseas specialists were sought last year for five specialties but it is the first time the HA has sought overseas experts for diagnostic radiology. Hospital Authority spokesman, Dr Ko Wing-man, said there was little difference between local and overseas terms except for the provision of return passages. He added the shortage in therapeutic radiographers was expected to ease in two years as the Hongkong Polytechnic was training personnel. The Sunday Morning Post today carries interviews with three nurses who tell of severe shortages which, in some cases, are putting patients at risk. In reply to points raised in the interviews, the Authority said the number of nurses including registered and student nurses totalled 16,240 by last December, compared with 15,770 in 1991, representing a net increase of 470. It said nurses could cope if the standard of care remained at the present level. The average years of experience among nursing staff had not dropped. The Authority also said the number of nurses assigned to a surgery depended on the complexity of the work.