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A fresh analysis of the data entered into the multicentre BIR fractionation trial of 3F/week versus 5F/week in radiotherapy of the laryngopharynx has been undertaken. Completed records of the 732 patients initially entered into the trial have now risen from 687 at the last report to 706. The data have been analysed in a manner similar to that adopted previously so as to measure the effects of the two regimes on both tumour and normal tissues, and some additional analyses have now also been made. There have been some modifications in the results in the various sub-groups which may be due to an inadequate number of patients having been followed up for long enough at the time of the previous analyses. More data for late radiation damage to normal tissues and new radiobiological findings have suggested possible explanations for the differences which have emerged between the two groups. The apparent differences between the sub-groups containing patients with highly localized tumours, which were reported in our prevous report, are now less marked and not statistically significant.

A detailed study has been made of the patients receiving routine post-operative radiotherapy in the Cancer Research Campaign trial for early breast cancer. Particular attention has been paid to the routine dose delivered and the incidence of recurrence in different areas. Little difference was apparent in the incidence of local recurrence in groups of patients receiving different levels of dosage, although there was a threefold reduction in five-year local recurrence-free rates compared with that for patients who received no irradiation. Moderate or severe telangiectasis occurred more frequently as the dose increased.When analysed in terms of survival, there was a tendency for the patients receiving more than 1510 ret to do a little better, but this was not statistically significant and could be due to some unexplained patient selection for higher dosage. There was no suggestion that irradiation might cause reduced survival.

A method of computing megavoltage dose distributions using an empirical mathematical model is described. The dose at a point in a medium is calculated as the product of a central axis percentage depth dose, a crossplot factor and a wedge factor. For a given set of conditions (i.e.type of machine, source-skin distance and wedge) 16 parameters are required to calculate the values of the three factors and hence the dose at any point. These parameters can be obtained from a relatively small number of experimental measurements. Dose distributions from a variety of different treatment machines have been computed by the method, and some comparisons of the calculated and measured doses have been made using “Goodness of Fit” score values. These show that the use of the method as a basis for computer treatment planning should be clinically acceptable.

A simple manual after-loading system for the treatment of carcinoma of the cervix has been developed. Radiochemical Centre J-type caesium sources are used made up in PVC tubes which can be inserted into PVC uterine tubes or rubber ovoids after these have been packed in position in the patient. Radiation exposure to theatre staff has been reduced by a factor of about four.

Preliminary data from a second British Institute of Radiology Fractionation Trial comparing short (≤4 weeks) and long (>4 weeks) overall treatment times are reported. The intake of patients ran from January, 1975 to December, 1985 when 611 patients with carcinoma of the laryngo-pharynx were registered in this prospective, randomized, multicentre clinical trial. No significant differences have, so far, been demonstrated between the two arms of the trial with respect to observed survival rates, tumour-free or laryngectomy-free rates. Further long-term follow-up is continuing.