A technique for total body irradiation in the treatment of patients with acute leukaemia

Abstract

Increasing interest is being shown in the use of bone marrow transplantation as part of the treatment of acute leukaemia (Thomas et al., 1977). Such transplantation requires intense courses of irradiation to the whole body (TBI) shortly before the bone marrow is injected. Doses of the order of 1000 cGy (rad) are commonly prescribed, usually in a single fraction. Ideally, such an irradiation requires a large treatment field covering the patient in a fully relaxed and comfortable position; to accommodate most individuals the field would need to be about two metres long. Few centres are equipped with treatment units designed for this requirement and, as an alternative, existing teletherapy equipment operating at an SSD or FSD of several metres has been used by some workers. Even this approach usually fails to yield an adequate field size because of the limited dimensions of the treatment rooms available. It is the purpose of this communication to describe the technique evolved at the Royal Marsden Hospital, where the largest field size which could be produced was 125 cm square. The dosimetry is also described; it may well be appropriate where more adequate treatment fields are available. The technique described was developed over several years and has now become routine. Some twenty or thirty patients are treated annually; this number is expected to continue to increase. When the bone marrow transplant programme was instituted the largest field size available was 125 cm × 125 cm between the 50% isodose levels.