Great importance attaches to the questions of relative radio sensibility, quantities absorbed, period of radiation, repeated or single treatment, auto-immunisation of the tissues to radia tion, and perhaps to that of the different effects of rays of different wave-lengths. These questions, however, cannot be con sidered here. They are, moreover, common to radiumtherapy and rontgentherapy. The biological superiority of gamma rays over X-rays is mainly due to the greater penetrative power of the gamma rays.
(I) Intracavitary Radiumtherapy.—This consists in introduc ing radioactive tubes, without rupturing the mucous membrane, into the natural cavities which form the site of a tumour or are close to a tumour. In such cases uncovered radium tubes are never used; the tubes are surrounded by light envelopes which not merely arrest the secondary radiation, but also, as far as possible, increase the focal distance. Many such applications of radium therapy have been abandoned. Those that survive affect cancers of the rectum, the prostate and bladder, and the uterus and vagina ; fibromyomata of the uterus and haemorrhagic metrop athies; and cancers of the buccal mucous membrance and the oesophagus.
Good palliative results can be obtained—sometimes readily, sometimes with difficulty—in most of the above-mentioned local isations of cancer. The only type of cancer, however, that is regularly cured—as often as by surgical treatment, and indeed probably more often—is the "pavement," cancer of the cervix uteri.
(2) Interstitial Radiumtherapy.—This consists in introducing the foci into the interior of the tissues through openings made for the purpose. In some cases a surgical operation is used as a mode of access (radium surgery). When possible, small foci are
introduced by injection through the skin or mucous membrane covering the area to be treated. This method embraces several processes, of which the two following are the chief. One (the American method) is to inject into the tissues, with a trocar and a fine style, minute glass or gold tubes ("seeds") containing radon, and to leave them there. The other (radium puncture) consists in temporarily planting needles in the tissues, fixing them by suturing, and withdrawing them when the treatment comes to an end. The advantage of radium puncture with platinum needles is that effective filtration is possible.
Interstitial curietherapy has been applied to most of the local isations of cancer. The most striking results have been obtained from it in cancers of the mouth, especially of the tongue, in which the prognosis has been considerably improved.
(3) Juxtacutaneous Radiumtherapy.—In the early days of radiumtherapy, one or more tubes of radium were applied direct to the skin and kept in place with an adhesive. Later, radium was incorporated in a varnish or enamel, which was spread on metal supports in geometrical shapes. These radiant surfaces were then applied to the skin, being kept from touching it by a very thin sheet of filtrative metal and a certain thickness of gauze. Such methods were not fit to survive, and have been displaced by that of making, as required, supports of plastic materials (e.g., a mix ture of wax, paraffin and sawdust, known as Columbia paste). A layer of such a material, of an even thickness suitable to the distance desired (5 mm., 1, 2, etc., cm.), is moulded under heat C) over the area to be treated and is then allowed to cool. Radium tubes containing equal quantities, whatever may be appropriate, are affixed to its outer surface at certain inter vals. By this method radiant surfaces are obtained which are exactly right for each individual case.
The juxtacutaneous plastic radiant surface method can be applied to the treatment of lesions (notably cancers) of the skin, certain mucous membranes, the pharynx, the larynx, the nipple, etc., and of cancerous adenopathies. It has greatly improved the results of radiumtherapy in squamocellular cancers of the skin and the orifices of the skin.