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HDR: Forget not “time” and “distance”
Inl. J Radialion Oncology Biol Phys., Vol. Printed in the U.S.A. All rights reserved.
20, pp.
I 13 I-I I32
0360.3016/91 $3.00 + .oO Copyright 0 I99 Pergamon Press plc
I
0 Editorial HDR: FORGET
NOT “TIME”
COLIN Gershenson
G. ORTON,
AND “DISTANCE” PH.D.
R.O.C., Wayne State University and Harper Hospital, Detroit, MI 48201 cervix cancer radiotherapy explained below.
Of all the principles we should have learned in over 90 years of brachytherapy, two of the most important are “time” and “distance.” Yet these two principles are often forgotten when new modalities such as high dose rate (HDR) remote afterloading are introduced into clinical practice. Let me explain.
that makes it so successful,
as
“DISTANCE” Intracavitary irradiation is highly effective in cervix cancer radiotherapy because we “put the dose where the tumor is”(W. E. Powers, personal communication, 199 1). At the same time, however, we have to be acutely aware that this carries with it the disadvantage that the distance to rectal and bladder tissues is also short, and extra care must be taken to protect these organs. Indeed, this latter represents a major advantage of the HDR modality in that it is apparently possible to pack and/or retract rectal and bladder tissues more effective than with LDR. Our survey results show that, on average, HDR rectal and bladder doses (compared to Pt. A) are about 20% lower than for LDR (4, 5). Presumably this is due to the better geometrical control possible with HDR hardware, and to the greatly reduced time which patients are required to tolerate each application. Nevertheless, packing and retraction are often not used for HDR treatments, and our survey shows that, in several facilities, the average relative doses to bladder and rectal tissues actually increased when converting from LDR to HDR (5). Unfortunately, a common reaction to increased complications has been to reduce the intracavitary component of the total dose, whereas the more appropriate action would have been to increase the fractionation and improve the geometry. We so firmly believe in the importance of fractionation in our institution, that for the past 3 years we have “superfractionated” our cervix cander HDR treatments, delivering 12 fractions of 3.86 Gy to Pt. A. A 12 fraction schedule was chosen in order to keep the dose-per-fraction to normal tissues within acceptable limits. We decided to keep rectal and bladder doses down to 2-2.5 Gy/fraction in order to be closer to the doses considered tolerable by fractionated teletherapy standards. Since our survey data (4, 5) indicated that HDR rectal/bladder doses were typ-
“TIME” It is vitally important that we allow enough time during the course of treatment to allow normal tissue cells to repair. With conventional brachytherapy this is achieved by keeping the dose rate low. Analogously, with HDR this equates to interposing many inter-fraction intervals during which repair can occur, that is, we fractionate appropriately. We all know this from teletherapy experience, yet there is ample evidence that this knowledge is frequently ignored when converting from LDR to HDR for the treatment of cervix cancer. Fractionation of these treatments detracts from the “convenience” of the HDR modality, which is one of its most attractive features, so there has been a tendency to compromise on this aspect of treatment and the results have usually been unfortunate, typically exemplified by an increase in complications. This is aptly illustrated by papers in this issue (2, 6) and also from a survey we have made of over 40 HDR users worldwide (4, 5). This survey shows that 15-20% of facilities employ two fractions or less, with Point A doses 8-9 Gylfraction. Increased normal tissue injury nearly always results, although there is some evidence that injury rates can be kept under control by painstaking protection of normal tissues by careful monitoring of rectal and bladder doses and extensive use of packing or retraction, and/or by reducing the intracavitary contribution and increasing the teletherapy component of the central pelvic dose. I believe this latter practice is fraught with danger and should be avoided at all costs, since it is the intracavitary nature of
Accepted for publication
Reprint requests to: Colin G. Orton, Ph.D.
1131
1 March 199 1.
1132
I. J. Radiation Oncology 0 Biology 0 Physics
ically about 60% of those to Pt. A, then this corresponds to Pt. A doses of 3.4-4.2 Gy/fraction. The linear-quadratic (L-Q) model (3) was then used to determine how many fractions of about 3.8 Gy to Pt. A would equate to the conventional LDR regimen we were replacing, viz., two fractions of 30 Gy at 0.5 Gy h-‘. This calculation yielded 12 fractions of 3.86 Gy. Note that 12 fractions of 3.86 Gy also equates to our average survey Pt. A schedule of 5-6 fractions of 7 Gy (4, 5) which gives some credence to in the use of the L-Q model for these calculations. Early results have been very promising (1).
May I, I99 I, Volume 20, Number 5 AN
URGENT
PLEA
I strongly urge all who use HDR therapy for curative patients to remember the importance of “time” and “distance.” Fractionate sufficiently and use adequate packing and/or retraction so that cells in normal tissues can repair efficiently, and so as not to make it necessary to compromise the intracavitary contribution to the total dose. Certainly this is inconvenient, time-consuming, and laborintensive, but I firmly believe that the potential benefits to patients are well worth the extra effort.
REFERENCES 1. Ahmad, K.; Kim, Y. H.; Orton, C. G.; Ezzell, G. A.; Deppe,
G.; Mesina, C.; Warmelink, C.; Malone, J.; Malviya, V.: Christenson, C.; Han, I. H.; Ratanatharathorn, V.; Herskovic, A. Fractionated high dose rate brachytherapy and concomitant teletherapy in the treatment of carcinoma of the cervix: technique and early results. Endocurietherapy/ Hyperthermia Oncol. (In Press). 2. Chen, M. S.; Lin, F. J.; Hong, C. H.; Tu, C. P.; Lan, J. H.; Tang, S. G.; Leung, W. M.; Wang, T. R. High-dose-rate afterloading technique in the radiation treatment of uterine cerivcal cancer: 399 cases and 9 years experience in Taiwan. Int. J. Radiat. Oncol. Biol. Phys. 20:915-919; 1991. 3. Dale, R. G. The application of the linear-quadratic dose-
effect equation to fractionated and protracted radiotherapy. Br. J. Radiol. 58:515-528; 1985. 4. Orton, C. G. A survey of HDR regimes used for cervix cancer radiotherapy. Proceedings of the Fifth Int. HDR Remote Afterloading Conference (Health Service Consults., South China, Maine), 52-60; 1990. 5. Orton, C. G. The importance of fractionation with high dose rate remote afterloading for cervix cancer. Int. J. Radiat. Biol. Phys. (submitted for publication.) 6. Van Lancker, M.; Storme, G. Prediction of severe late complications in fractionated high dose-rate brachytherapy in gynecological applications. Int. J. Radiat. Oncol. Biol. Phys. 20:1125-l 129; 1991.
20, pp.
I 13 I-I I32
0360.3016/91 $3.00 + .oO Copyright 0 I99 Pergamon Press plc
I
0 Editorial HDR: FORGET
NOT “TIME”
COLIN Gershenson
G. ORTON,
AND “DISTANCE” PH.D.
R.O.C., Wayne State University and Harper Hospital, Detroit, MI 48201 cervix cancer radiotherapy explained below.
Of all the principles we should have learned in over 90 years of brachytherapy, two of the most important are “time” and “distance.” Yet these two principles are often forgotten when new modalities such as high dose rate (HDR) remote afterloading are introduced into clinical practice. Let me explain.
that makes it so successful,
as
“DISTANCE” Intracavitary irradiation is highly effective in cervix cancer radiotherapy because we “put the dose where the tumor is”(W. E. Powers, personal communication, 199 1). At the same time, however, we have to be acutely aware that this carries with it the disadvantage that the distance to rectal and bladder tissues is also short, and extra care must be taken to protect these organs. Indeed, this latter represents a major advantage of the HDR modality in that it is apparently possible to pack and/or retract rectal and bladder tissues more effective than with LDR. Our survey results show that, on average, HDR rectal and bladder doses (compared to Pt. A) are about 20% lower than for LDR (4, 5). Presumably this is due to the better geometrical control possible with HDR hardware, and to the greatly reduced time which patients are required to tolerate each application. Nevertheless, packing and retraction are often not used for HDR treatments, and our survey shows that, in several facilities, the average relative doses to bladder and rectal tissues actually increased when converting from LDR to HDR (5). Unfortunately, a common reaction to increased complications has been to reduce the intracavitary component of the total dose, whereas the more appropriate action would have been to increase the fractionation and improve the geometry. We so firmly believe in the importance of fractionation in our institution, that for the past 3 years we have “superfractionated” our cervix cander HDR treatments, delivering 12 fractions of 3.86 Gy to Pt. A. A 12 fraction schedule was chosen in order to keep the dose-per-fraction to normal tissues within acceptable limits. We decided to keep rectal and bladder doses down to 2-2.5 Gy/fraction in order to be closer to the doses considered tolerable by fractionated teletherapy standards. Since our survey data (4, 5) indicated that HDR rectal/bladder doses were typ-
“TIME” It is vitally important that we allow enough time during the course of treatment to allow normal tissue cells to repair. With conventional brachytherapy this is achieved by keeping the dose rate low. Analogously, with HDR this equates to interposing many inter-fraction intervals during which repair can occur, that is, we fractionate appropriately. We all know this from teletherapy experience, yet there is ample evidence that this knowledge is frequently ignored when converting from LDR to HDR for the treatment of cervix cancer. Fractionation of these treatments detracts from the “convenience” of the HDR modality, which is one of its most attractive features, so there has been a tendency to compromise on this aspect of treatment and the results have usually been unfortunate, typically exemplified by an increase in complications. This is aptly illustrated by papers in this issue (2, 6) and also from a survey we have made of over 40 HDR users worldwide (4, 5). This survey shows that 15-20% of facilities employ two fractions or less, with Point A doses 8-9 Gylfraction. Increased normal tissue injury nearly always results, although there is some evidence that injury rates can be kept under control by painstaking protection of normal tissues by careful monitoring of rectal and bladder doses and extensive use of packing or retraction, and/or by reducing the intracavitary contribution and increasing the teletherapy component of the central pelvic dose. I believe this latter practice is fraught with danger and should be avoided at all costs, since it is the intracavitary nature of
Accepted for publication
Reprint requests to: Colin G. Orton, Ph.D.
1131
1 March 199 1.
1132
I. J. Radiation Oncology 0 Biology 0 Physics
ically about 60% of those to Pt. A, then this corresponds to Pt. A doses of 3.4-4.2 Gy/fraction. The linear-quadratic (L-Q) model (3) was then used to determine how many fractions of about 3.8 Gy to Pt. A would equate to the conventional LDR regimen we were replacing, viz., two fractions of 30 Gy at 0.5 Gy h-‘. This calculation yielded 12 fractions of 3.86 Gy. Note that 12 fractions of 3.86 Gy also equates to our average survey Pt. A schedule of 5-6 fractions of 7 Gy (4, 5) which gives some credence to in the use of the L-Q model for these calculations. Early results have been very promising (1).
May I, I99 I, Volume 20, Number 5 AN
URGENT
PLEA
I strongly urge all who use HDR therapy for curative patients to remember the importance of “time” and “distance.” Fractionate sufficiently and use adequate packing and/or retraction so that cells in normal tissues can repair efficiently, and so as not to make it necessary to compromise the intracavitary contribution to the total dose. Certainly this is inconvenient, time-consuming, and laborintensive, but I firmly believe that the potential benefits to patients are well worth the extra effort.
REFERENCES 1. Ahmad, K.; Kim, Y. H.; Orton, C. G.; Ezzell, G. A.; Deppe,
G.; Mesina, C.; Warmelink, C.; Malone, J.; Malviya, V.: Christenson, C.; Han, I. H.; Ratanatharathorn, V.; Herskovic, A. Fractionated high dose rate brachytherapy and concomitant teletherapy in the treatment of carcinoma of the cervix: technique and early results. Endocurietherapy/ Hyperthermia Oncol. (In Press). 2. Chen, M. S.; Lin, F. J.; Hong, C. H.; Tu, C. P.; Lan, J. H.; Tang, S. G.; Leung, W. M.; Wang, T. R. High-dose-rate afterloading technique in the radiation treatment of uterine cerivcal cancer: 399 cases and 9 years experience in Taiwan. Int. J. Radiat. Oncol. Biol. Phys. 20:915-919; 1991. 3. Dale, R. G. The application of the linear-quadratic dose-
effect equation to fractionated and protracted radiotherapy. Br. J. Radiol. 58:515-528; 1985. 4. Orton, C. G. A survey of HDR regimes used for cervix cancer radiotherapy. Proceedings of the Fifth Int. HDR Remote Afterloading Conference (Health Service Consults., South China, Maine), 52-60; 1990. 5. Orton, C. G. The importance of fractionation with high dose rate remote afterloading for cervix cancer. Int. J. Radiat. Biol. Phys. (submitted for publication.) 6. Van Lancker, M.; Storme, G. Prediction of severe late complications in fractionated high dose-rate brachytherapy in gynecological applications. Int. J. Radiat. Oncol. Biol. Phys. 20:1125-l 129; 1991.