Br. J. Cancer (1978) 37, Suppl. III, 307
UNCONVENTIONAL FRACTIONATION IN CLINICAL RADIOTHERAPY L. R. HOLSTI, M. SALMO AND M. M. ELKIND* From the Department of Radiotherapy, University Central Hospital, Helsinki 29, Finland, the Division of Biological and Medical Research, Argonne National Laboratory, Argonne, Illinois 60439, and the Department of Radiology, University of Chicago, Chicago, Illinois 60637, U.S.A.
Summary.-Radiotherapy with decreasing individual tumour doses has been used in treatment of lung metastases and carcinomas. Treatment given with this unconventional schedule is more effective than conventional radiotherapy based upon equal doses and equal intervals. Tumours could be classified into 2 groups according to the shrinkage rate. In the group shrinking more rapidly, tumours totally disappeared in most instances; furthermore, in most instances, tumours in this more responsive group could be identified because in the week after the first fraction they had already started to shrink.
THE TIME needed for reoxygenation to have a significant effect in radiotherapy is obviously inadequate when daily fractionations with equal doses and equal intervals are used. Strategies to intensify the degree of reoxygenation by varying the fraction size and the fraction intervals have been presented by Elkind, Withers and Belli ( 1968), Elkind (1974). A reasonable large degree of cell killing might be required before significant amounts of cell lysis and attendant reoxygenation set in. This suggests that at the beginning, reasonably large doses might be best and that these might have to be separated by intervals of 3-4 or possibly more cell-cycle times. Once tumour shrinkage and reoxygenation have started, optimal treatment could require smaller dose fractions and shorter intervals, the latter to ensure that contributions from repopulation remain ineffective.
patients with 8 lung metastases or primary lung cancer served as controls. Three of them were treated with conventional fractionation 200 rad per day, 25 fractions in 5 weeks, and 3 with daily fractionated split-course therapy 220 rad per day, total dose being 5500 rad in 8 weeks (CFS). The treatment was given with a 10 MeV Linear accelerator from 2 opposing ports, the field size being as small as possible to cover the tumour. Chest X-rays were taken once a week to follow the change in size of the irradiated tumours.
MATERIAL AND METHODS
TABLE I.-The Unconventional Fractionation Scheme (UFS)
RESULTS
To calculate the shrinkage of the area of the tumours, the following equation was used: A Aoe-bT Ao = constant; b = shrinking factor; T -time. An analysis of the slopes indicated that
Based on these ideas, the following unconMon. Tues. Wed. Thur. Fri. ventional fractionation scheme (UFS) (Table Week 1 racl 1000 I), proposed by Elkind has been tested in 700 500 2 clinical material. Seventeen patients with 25 300 300 300 3 lung metastases or primary lung carcinomas 300 300 300 4 200 200 200 200 200 5 were treated according to this schedule. Six * Participation in this work supportecl by the United States Energy Research and Development Administration.
308
L. R. HOLSTI, M. SALMO AND M. M. ELKIND
100 c)
cn c)
70
w
50 H LA.
0
'CJ
40
30
-LJ
cc
20 10 15 20 WE E K S FiG. 1.-The tumours of UFS group divided into 2 subgroups: (x) well reacting group with shrinking factor b = -0-0268 and (0) poorly reacting group with shrinking factor b = -0-0095. 1
5
C/)
w cn < 130 cn
w
100
2 U-
0
UNCONVENTIONAL FRACTIONATION IN CLINICAL RADIOTHERAPY L. R. HOLSTI, M. SALMO AND M. M. ELKIND* From the Department of Radiotherapy, University Central Hospital, Helsinki 29, Finland, the Division of Biological and Medical Research, Argonne National Laboratory, Argonne, Illinois 60439, and the Department of Radiology, University of Chicago, Chicago, Illinois 60637, U.S.A.
Summary.-Radiotherapy with decreasing individual tumour doses has been used in treatment of lung metastases and carcinomas. Treatment given with this unconventional schedule is more effective than conventional radiotherapy based upon equal doses and equal intervals. Tumours could be classified into 2 groups according to the shrinkage rate. In the group shrinking more rapidly, tumours totally disappeared in most instances; furthermore, in most instances, tumours in this more responsive group could be identified because in the week after the first fraction they had already started to shrink.
THE TIME needed for reoxygenation to have a significant effect in radiotherapy is obviously inadequate when daily fractionations with equal doses and equal intervals are used. Strategies to intensify the degree of reoxygenation by varying the fraction size and the fraction intervals have been presented by Elkind, Withers and Belli ( 1968), Elkind (1974). A reasonable large degree of cell killing might be required before significant amounts of cell lysis and attendant reoxygenation set in. This suggests that at the beginning, reasonably large doses might be best and that these might have to be separated by intervals of 3-4 or possibly more cell-cycle times. Once tumour shrinkage and reoxygenation have started, optimal treatment could require smaller dose fractions and shorter intervals, the latter to ensure that contributions from repopulation remain ineffective.
patients with 8 lung metastases or primary lung cancer served as controls. Three of them were treated with conventional fractionation 200 rad per day, 25 fractions in 5 weeks, and 3 with daily fractionated split-course therapy 220 rad per day, total dose being 5500 rad in 8 weeks (CFS). The treatment was given with a 10 MeV Linear accelerator from 2 opposing ports, the field size being as small as possible to cover the tumour. Chest X-rays were taken once a week to follow the change in size of the irradiated tumours.
MATERIAL AND METHODS
TABLE I.-The Unconventional Fractionation Scheme (UFS)
RESULTS
To calculate the shrinkage of the area of the tumours, the following equation was used: A Aoe-bT Ao = constant; b = shrinking factor; T -time. An analysis of the slopes indicated that
Based on these ideas, the following unconMon. Tues. Wed. Thur. Fri. ventional fractionation scheme (UFS) (Table Week 1 racl 1000 I), proposed by Elkind has been tested in 700 500 2 clinical material. Seventeen patients with 25 300 300 300 3 lung metastases or primary lung carcinomas 300 300 300 4 200 200 200 200 200 5 were treated according to this schedule. Six * Participation in this work supportecl by the United States Energy Research and Development Administration.
308
L. R. HOLSTI, M. SALMO AND M. M. ELKIND
100 c)
cn c)
70
w
50 H LA.
0
'CJ
40
30
-LJ
cc
20 10 15 20 WE E K S FiG. 1.-The tumours of UFS group divided into 2 subgroups: (x) well reacting group with shrinking factor b = -0-0268 and (0) poorly reacting group with shrinking factor b = -0-0095. 1
5
C/)
w cn < 130 cn
w
100
2 U-
0
