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Patient recruitment is an important issue in the feasibility study of a hadron therapy programme such as Med-AUSTRON. Data on cancer incidence in Europe, Austria, and neighbouring countries are reviewed for the most frequent tumors suitable for charged particle therapy. From these data, the numbers of potential patients suitable for MED-AUSTRON are derived for each tumor site by applying the coefficients proposed in the EULIMA-1992 feasibility study. Whatever the assumptions made, a sufficient and adequate recruitment for MED-AUSTRON can be expected. However, an appropriate referring system has to be established within Austria and also in the neighbouring countries.

EORTC protocol 22791 compared once daily fractionation (CF) of 70 Gy in 35-40 fractions in 7-8 weeks, to pure hyperfractionation (HF) of 80.5 Gy in 70 fractions in 7 weeks using 2 fractions of 1.15 Gy per day, in T2-T3 oropharyngeal carcinoma (excluding base of tongue), N0,N1 of less than 3 cm. From 1980 to 1987, 356 patients were entered. In the final analysis (June 1990), the local control was significantly higher (p = 0.02 log-rank) after HF compared with CF. At 5 years, 59% of patients are local disease-free in the HF arm compared to 40% in the CF arm. The superiority of HF was demonstrated in patients staged T3N0,T3N1 but not in T2. The Cox model confirmed that the treatment regimen was an independent significant prognostic factor for locoregional control (p = 0.007 log-rank). This improvement of locoregional control was responsible for a trend to an improved survival (p = 0.08 log-rank). There was no difference in late normal tissue damage between the two treatment modalities.

Mailed dosimetry, using thermoluminescent dosimeters, can play an important role in quality assurance procedures in radiotherapy. In 1989, a pilot study was started with the main aim to show the feasibility of this method for the multicentre EORTC trial 22881 on the conservative management of breast carcinoma. Two anthropomorphic breast phantoms and six patients with breast carcinoma were irradiated according the prescriptions of the protocol. TLD measurements of the entrance and exit dose were performed in 6 MV tangential X-ray beams. It proved to be possible to correlate the dose measured in the entrance and exit points of the beams to the calculated dose closely under the surface. A thickness of at least 5 mm bolus material must be applied over the dosimeters and a distance of at least 3 cm from the lateral and medial field borders must be maintained in order to reach a clinically acceptable accuracy in the measurements.

The IAEA 1987 protocol is an international protocol which has made a number of improvements over the AAPM 1983 protocol for calibration of high-energy photon and electron beams. We present a detailed numerical comparison between the two protocols by calculating (i) Ngas and ND for PTW (PMMA wall), Capintec (air-equivalent plastic wall) and NEL (graphite wall) Farmer type ionization chambers for 60Co gamma rays; (ii) dose-to-water with chamber in water irradiated by 4- or 25-MV x rays; (iii) dose-to-water with chamber in water, PMMA, and polystyrene phantoms irradiated by 5- and 10-MeV electrons; and (iv) dose-to-water with chamber in water irradiated by 20-MeV electrons. For photons, the IAEA protocol gives results which are in good agreement with the AAPM protocol; on average the IAEA results are 0.6% smaller than the AAPM results while discrepancies between the two are in the range of -0.4% to -1.2%. For 10-MeV electrons also, the IAEA protocol gives results which are in excellent agreement with the AAPM protocol; on average the IAEA results are 0.3% smaller than the AAPM results while discrepancies between the two are in the range of -1.0% to +0.5%. In contrast to the above, for 5-MeV electrons, the IAEA protocols give results smaller than the AAPM protocol by 2.0% on average with discrepancies between protocols ranging from -4.1% to -0.7% depending upon the ionization chamber and phantom material used. For 5-MeV electrons, the discrepancies are particularly large for polystyrene phantom; the average discrepancies being -1.4%, -1.1%, and -3.6% for water, PMMA, and polystyrene, respectively. If data for 5-MeV electrons with polystyrene phantom are excluded, then the overall agreement between the two protocols for photons and electrons is within the range of -1.9% to +0.5%. Principal reasons for the observed discrepancies are (i) IAEA uses the correct expression for ND resulting in up to +0.8% correction; (ii) IAEA uses the most recent stopping power ratio for graphite-to-air resulting in up to +0.5% correction; (iii) IAEA uses a correction of up to +0.8% for the central electrode which AAPM ignores; (iv) the present estimates of the percent depth doses which arise from the differences in measurement depths in the two protocols; and (v) IAEA uses measured values of the fluence correction factor while AAPM uses a theoretical estimate resulting in corrections of up to -2.2%.

The introduction of high LET radiations into radiotherapy is an exciting development. Neutron facilities are already in clinical use in England and the United States, while machines to produce negative pi mesons and high energy heavy ions are in an advanced stage of development in Canada, the United States and Europe. The state of the art at each of these installations is reviewed. The therapeutic merits of various heavy particles are compared with conventional photon beams. Lowering the OER (oxygen enhancement ratio) and improvement in the depth dose pattern are the principal advantages sought. Neutrons result in a somewhat lower OER but offer depth-dose patterns that are barely the equal of x- and gamma-rays. Protons by contrast produce excellent dose distributions, but no reduction of OER. Negative pi mesons improve both depth dose pattern and OER to some extent. High energy heavy nuclei show the greatest promise as far as lowering the OER is concerned, but will probably not equal pions in depth dose pattern. More radiobiologic data are urgently needed for all of these new radiation modalities.