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The radiobiological data obtained from a multicentre clinical trial of the British Institute of Radiology, which compared the treatment of carcinoma of the laryngo-pharynx by 3 fractions per week (3F/wk) with 5 fractions per week (5F/wk) radiotherapy, have been studied. The trial involved an intake of 734 patients between 1966 and 1975. The number of fractions, overall treatment time and total doses used by different treatment centres ranges from 9 to 40 fractions, 18 to 70 days and 3880 to 7800 cGy, respectively. An 11-13% reduction in the total radiation dose was applied for treatments with 3F/wk as compared with 5F/wk in centres treating over 6 weeks and 3 weeks, respectively. All patients were followed for 10 years from the start of treatment. Different types of early and late normal-tissue reactions were investigated, ranging from a low percentage incidence of perichondritis to 95% for slight early reactions. Greater than 80% of the late normal-tissue reactions seen were observed within the first year after the start of treatment, and 96% were observed within the first 5 years. There was no statistically significant difference in the normal-tissue event-free rates between the 3F/wk and 5F/wk treatment groups. This finding did not differ when different major treatment centres were studied separately. For a number of end-points, alpha/beta ratios and N- and T-exponents of a modified nominal standard dose (NSD) formula have been calculated.

The second British Institute of Radiology trial of dose fractionation in radiotherapy compared two groups of prospectively randomized patients with squamous carcinoma of the laryngo-pharynx; one group was treated in a short (less than or equal to 4 weeks) and the other in a long (greater than 4 weeks) overall time. Treatment in any one centre could be given, with no planned gap in the course of treatment, either as a conventional, daily (5 fractions per week regime) or as 3 fractions per week. A total of 611 patients were allocated to treatment, of whom nine have had to be excluded from the analysis for a lack of information. Patients were admitted to the trial from January 1976 to December 1985 and were followed up for a maximum of 10 years and a minimum of 3 years. A reduction in total dose was made for use in the short compared with the long treatment regime. This reduction in total dose varied between 18% and 22% depending on whether 5 fractions or 3 fractions per week regimes were used. Overall, no statistically significant differences have been found between the two arms of the trial. The patients treated with 5 fractions per week in a short overall treatment time showed fewer late normal tissue effects. An analysis based on stratification by age, stage and anatomical site gave a relative risk (short/long overall treatment time) for deaths of 1.23 with a 95% confidence interval from 0.96 to 1.59. Analyses stratified for stage and site gave relative risks with 95% confidence intervals of 1 x 10 (0.84-1.44) for local recurrences/tumour persistence, and 1.01 (0.70-1.45) for laryngectomies.

The 10 year follow-up of a clinical trial involving the comparison of 3F/wk versus 5F/wk in radiotherapy of squamous cell carcinoma of the larynx and hypopharynx has now been completed. The trial involved an intake of 734 patients between 1966 and 1975. The classification of all patients has been revised to conform with the latest TNM publication. A reduction in total dose was made for 3F/wk compared with 5F/wk. This varied between 13% and 11% in centres treating over 3 weeks and 6 weeks, respectively. No statistically significant differences have been found between the two arms (3F/wk versus 5F/wk) of the trial in any of the main group analyses. A number of sub-group analyses relating to survival, tumour-free and laryngectomy-free rates and to the comparison of acute or late normal-tissue radiation damage have also been performed. No differences have been found that could be considered to be statistically significant in relation to the particular sub-group. Previous interim reports suggested minor differences in sub-group analyses between the 3F/wk and 5F/wk regimes in this trial; these have diminished now that the full follow-up data are available. This trial has provided evidence on which clinicians may base their choice between either a 3F/wk fractionation regime or a conventional 5F/wk treatment protocol in the treatment of carcinoma of the laryngo-pharynx.

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 previous report, are now less marked and not statistically significant.

A programmed graphics terminal has been connected on-line to a large time-shared computer for calculating dose distributions in radiotherapy treatment planning and provides a viable alternative to dedicated systems and batch working. The terminal equipment is based on a mini-computer and includes a function-key devise for outline input, a large-screen refresh oscilloscope for viewing results and an X-Y plotter for hard-copy. Radiotherapy dose computation programs in standard Fortran are stored and run on a large remote computer with graphical interaction at the terminal. External beam programs can calculate dose distributions for most commonly used treatment situations and can compute in off-axis planes. Data input is fully interactive and easy to understnad. Dose distributions are displayed as isodose contours. Advantages of the system include accuracy, speed, ease of use and maintenance, and transferability of the programs between different host computers.

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.

The results are reported of the multicentre BIR fractionation trial of 3F/week versus 5F/week in radiotherapy of the laryngo-pharynx. 687 patient records have been analysed with respect to survival rates, recurrence-free rates and laryngectomy-free rates. For the group as a whole these analyses show no difference between the two fractionation regimes. Analysis of the sub-group which had early disease confined to the vocal cords does, however, show a better recurrence-free and laryngectomy-free rate for those patients treated with 5F/week, though the survival rate for the two groups remains similar. Acute and late normal tissue reactions are reported for up to six years after treatment. It appears that treatment with 3F/week can be given safely to patients with advanced disease. The differences between the two treatment groups who had early disease of the vocal cords are discussed, but until more data become available in the future the problems raised cannot be resolved.

Preliminary data from a second British Institute of Radiology Fractionation Trial comparing short (less than or equal to 4 weeks) and long (greater than 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.

A computer-based system for radiotherapy clinical records is described. Its main features are the use of a single mark-sense form for input of data at all stages of the patient's progress, and the provision of a plain language print-out of the patient's record after each updating. The programs are written in Fortran and are implemented on a Rank Xerox Sigma 6 computer.

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 or higher dosage. There was no suggestion that irradiation might cause reduced survival.

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.