Selected abstracts from Radiotherqv and Oncology 69

HYPOFRACTIONATED RADIOTHERAPY AS PALLIATIVE TREATMENT IN POOR PROGNOSIS PATIENTS WITH HIGH GRADE GLIOMA

R. Thomas,” N. James,= D. Guerrero,” S. Ashley,b A. Gregor,’ M. Brada”

“Neuro-oncology Unit and Academic Unit of Radiotherapy and Oncology, The Royal Marsden Hospital and Institute of Cancer Research, Downs Road, Sutton, Surrey SM2 5PT, UK; bComputing Department, The Royal Marsden Hospital and Institute of Cancer Research, Downs Road, Sutton, Surrey SM2 5PT, UK; ‘Department of Clinical Oncology, Western General Hospital, Crewe Road, Edinburgh, EH4 2XU, UK

Vol. 33, 1994, pp. 113-l 16

Key words: Barthel index; Kamofsky performance status; Elderly patients; Disabled patients; Phase II study

We report the palliative effectiveness of a hypofractionated radiotherapy regimen in patients with poor prognosis high grade glioma. Thirty-eight elderly, and/or disabled patients received radiotherapy to a dose of 30 Gy in 6 fractions over 2 weeks to a planning target volume defined by the enhancing tumour and a 2-cm margin. The median survival was 6 months with a l-year survival rate of 23%. Treatment was without acute toxicity. One month after radiotherapy, func- tional status, assessed using a verbally administered Barthel index, improved in 38% and remained stable in a further 39% of surviving patients. At 3 months 39% of surviving patients had improved and a further 12% remained stable. We conclude that in the poor prognostic group of patients with high grade glioma hypofractionated partial brain radio- therapy is well tolerated, convenient and provides effective palliation in a proportion of patients. Comparison with con- ventional radiotherapy or symptomatic care alone require further evaluation in randomised studies. SSDI 0167-8140(94)01475-I

THE EFFECT OF TUMOUR SHRINKAGE ON BIOLOGICALLY EFFECTIVE DOSE, AND POSSIBLE IMPLICATIONS FOR FRACTIONATED HIGH DOSE RATE BRACHYTHERAPY

R. G. Dale,” Bleddyn Jonesb

aDepartment of Medical Physics, Charing Cross Hospital, London W6 8RF, UK; ‘Clatterbridge Centre for Oncology, Bebington, Wirral, Merseyside L63 4JY, UK

Vol. 33, 1994, pp. 125-132

Key words: Biologically effective dose; Linear-quadratic; Tumour shrinkage; High dose rate brachytherapy

A method for incorporating a tumour shrinkage factor into linear-quadratic (LQ) brachytherapy equations is proposed.

When there is a significant degree of ongoing shrinkage throughout a course of brachytherapy, and when the sources are centrally situated within the tumour volume, the biologi- cally effective dose (BED) to the tumour will be higher than that which is calculated with standard equations. Although the analytical method initially assumes that shrinkage is ex- ponential with time, it is shown that the modified equations (for both high and low dose rate brachytherapy ) are essen- tially analogous to existing BED equations, but with the addition of a simple linear time-dependent factor. In this article, which concentrates on the implications for fraction- ated high dose-rate brachytherapy, it is demonstrated that increasing the time interval between fractions will only im- prove the BED in some cases, the conditions for which may be identified in terms of the ratio K/z, where K is the daily dose required to combat tumour repopulation and z is the daily linear shrinkage rate. In the absence of predictive assay techniques, or where there is doubt as to whether or not the radiobiological conditions favour an increase in the interval between each dose delivery, relatively close spacing (i.e. acceleration) of brachytherapy fractions appears to be the most prudent option. SSDI 0167~8140( 94)01448-C

VERIFICATION OF SOURCE POSITION IN INTERSTITIAL AND INTRALUMENAL BRACHYTHERAPY

A. van’t Riet, A. C. A. Mak, H. J. te Loo, C. J. M. Hoekstra. V. G. M. Althof

RISO, Radiotherapy and Curietherapy, Fesevurstraat 11, 7415 CM Deventer, The Netherlands

Vol. 33, 1994, pp. 167-170

Key words: Brachytherapy; Quality assurance; Verification imaging

In brachytherapy afterloading, the treatment is simulated us- ing dummy sources. In this study, imaging during treatment was performed to see whether the radioactive sources accu- rately replaced the dummy sources. In low-dose rate afterloading (manually or remote controlled) X-ray radiog- raphy was applied for verification. In high dose rate afterloading, the radioactive source was visualised under re- mote controlled X-ray fluoroscopy. Differences between dummy and treatment source position were observed, justi- fying verification imaging in brachytherapy. SSDI 0167-8140(94)01450-H