Dosage Distribution and Dosage in Carcinoma of the Uterine Cervix

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Abstract
This paper will describe briefly the Manchester approach to the treatment of carcinoma of the uterine cervix under three main headings: (a) what we wanted to do when in 1937 we started working on this subject; (b) how we decided to do it; (c) the results we have obtained and conclusions that we can draw from them. What we wished to do was to treat carcinoma of the uterine cervix and to do so primarily by means of radium. More than this, it was regarded as essential that any method we should devise must be such that we could easily calculate and state the number of roentgens delivered, for it is only when dosage is expressed in terms of roentgens that any real progress can be made. A further requirement was that the method to be devised should be capable of delivering the same dose in roentgens regardless of the size of the patient or the size and shape of the tumour being treated. Any radiological method must be able to produce a high dose zone which is roughly the shape of the tumours that are likely to be met in practice. In the case of carcinoma of the uterine cervix, this shape is not a simple one. The tumour involves part or all of the cervix, its predominant line of spread is laterally through the paracervical tissues into the parametrium, while it may also extend upwards into the uterus as far as the fundus, and downwards into the vagina, growing over the vault in any direction. Rarely, however, except in very advanced cases, does the tumour infiltrate forward into the bladder or backwards into the rectum, so that we are left with having to treat a zone which is roughly trefoil in section and has small thickness forwards or backwards. When this work was started, Paterson and Parker (1) had just completed their now famous dosage system and we should very much have liked to have been able to apply this system to treatment of carcinoma of the cervix, but this was considered impracticable and we had to employ, like Stockholm and Paris before us, an intracavitary method. Thus we cannot achieve homogeneity of irradiation and have to be content with a dose which falls from the radium outwards. This in turn means that we must select some point at which to state our dosage in roentgens. In the choice of this point, three main considerations arise. First, it must be anatomically comparable from patient to patient; second, the dose there must not be highly sensitive to small alterations in the position of the radium which do not materially affect the treatment as a whole; finally, most important of all, it must be such that it can be used for the correlation of general radiation effect with radiation dose. Our choice of point was guided by the work of T. F. Todd (2), which showed that the initial lesion of radiation necrosis is due ordinarily to high dosage in the region where the uterine blood vessels are crossed by the ureter. This region we have called the paracervical triangle (3), its approximate position being shown in Figure 1.

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