- Email: [email protected]
In response to Drs. Cameron and Cornes
Int. J. Radiation Oncology Biol. Phys., Vol. 66, No. 3, pp. 956 –957, 2006 Copyright © 2006 Elsevier Inc. Printed in the USA. All rights reserved 0360-3016/06/$–see front matter
LETTERS TO THE EDITOR BRACHYTHERAPY VS. IMRT FOR IRRADIATION OF THE VAGINAL VAULT: IN REGARD TO AYDOGAN ET AL. (INT J RADIAT ONCOL BIOL PHYS 2006;65:266 –273)
location and its implication for intracavitary brachytherapy radiation treatment. Brachytherapy 2005;4:236 –240.
To the Editor: We congratulate Aydogan et al. (1) on developing the field of intensity-modulated radiotherapy (IMRT) with their article comparing dosimetry of IMRT to high-dose-rate (HDR) brachytherapy for irradiation of the vaginal vault in endometrial cancer. However, we feel that there are still good reasons to treat with HDR brachytherapy. The beauty of vault HDR brachytherapy is that planning target volume (PTV) is essentially equivalent to clinical target volume (CTV) because the applicator is an immobilization device. Intensity-modulated RT must allow a margin for setup inaccuracies and internal organ motion; otherwise, we risk geographic miss. Standard patient immobilization for pelvic radiotherapy is accurate to 2– 4 mm compared with bony anatomy (2). Obesity, frequent in endometrial cancer, can greatly increase this. Internal organ movement of the vault has not been accurately assessed, but its proximity to the rectum and bladder makes it susceptible to movement secondary to changes in their filling. Groups introducing IMRT for pelvic radiotherapy in gynecologic cancer have expanded CTV by 1 cm to create the PTV to counter geographic miss (3). Aydogan et al. have not made any allowance for the PTV margin in this analysis. Even with a reproducible immobilization technique, PTV margin will need to be taken into account. It is these dosimetric data that will need to be planned and then compared with HDR brachytherapy dosimetry to give a realistic comparison. Aydogan modeled a 3-cm diameter applicator treating 4 cm of vagina, dosed to 0.5-cm depth. An additional 0.5-cm uncertainty margin increases PTV from 28.2 cm3 to 76.2 cm3! The article compares maximum dose points in organs at risk; however, in brachytherapy, because of the high-dose fall off and uncertainties in calculations, these are not usually considered clinically relevant (4). Instead, it may be more appropriate to compare highest dose with a contiguous area of the organs at risk (e.g., 0.1 cm3) (4). Comment is made on the dose nonuniformity of the HDR plan compared with the IMRT plan. This can be considered as a further advantage of brachytherapy over IMRT. The aim of vaginal vault irradiation is to irradiate the vaginal vault lymphatics. In 97% of cases with a stretched vagina, these occur within 3 mm of the vaginal surface (5). This area receives ⬎100% of the prescribed dose (where dose is prescribed to 0.5 cm, as is our practice) from vaginal vault brachytherapy. Therefore, for a similar dose at 0.5 cm, the vaginal vault lymphatics will receive a considerably higher dose with brachytherapy than IMRT, which may have clinical significance.
IN RESPONSE TO DRS. CAMERON AND CORNES To the Editor: There has been a great interest in intensity-modulated therapy (IMRT) as an alternative to brachytherapy in recent years (1– 6). With regard to the role of IMRT in the treatment of the vaginal vault, Drs. Cameron and Cornes raise a number of interesting and important points. We agree that IMRT requires an additional margin to account for internal motion, intrafractional uncertainties, and setup error. However, inclusion of such margin in IMRT does not necessarily result in a larger dose to the surrounding organs at risk (OAR) in comparison to brachytherapy (5). In addition, a margin may also be required for high-dose-rate (HDR) brachytherapy (7, 8). A systematic study is needed to quantify the uncertainty associated with vaginal cylinder placement because there are no published studies, to our knowledge, which investigate it. For IMRT to be successful in this disease site, it must be used in conjunction with a suitable immobilization method to reduce organ motion and setup error (9). Thus, in our study, we proposed the use of an internal immobilization system consisting of a vaginal cylinder and an indexing mechanism. Such a device may also be used to reduce intrafractional errors when it is used as surrogate in an image-guided approach. Evaluation of the internal immobilization device is under way at our institution. Vaginal vault HDR brachytherapy also has several limitations that may be overcome with IMRT. For example, the tumor volume often extends deeper in the perivaginal and parametrial tissues, particularly in women with recurrent disease. With an HDR cylinder, it is impossible to treat deeper or irregularly shaped tumors without irradiating the OAR to a much higher dose than the prescription dose. With IMRT, the dose can be sculpted to the shape of the planning target volume while minimizing the dose to surrounding normal tissue. These characteristics may allow IMRT to be used in patients who are unable to receive brachytherapy because of recurrence, irregular pelvic anatomy, medical problems, or poor tumor regression with external beam radiotherapy. In conclusion, we agree with Drs. Cameron and Cornes’ concerns on the widespread adoption of IMRT for this disease site before a rigorous clinical evaluation. However, with a suitable internal immobilization device used in conjunction with image-guided technologies, our approach may provide a comparable or better dose distribution than HDR brachytherapy. Clearly, a well-designed prospective clinical trial is needed to determine the efficacy and safety of this approach.
ALISON CAMERON PAUL CORNES, B.M.B.CH., M.R.C.P. Department of Clinical Oncology Bristol Haematology and Oncology Centre Bristol, United Kingdom
BULENT AYDOGAN, PH.D. JOHN C. ROESKE, PH.D. Department of Radiation and Cellular Oncology University of Chicago Chicago, IL
doi:10.1016/j.ijrobp.2006.07.016 1. Aydogan B, Mundt AJ, Smith BD, et al. A dosimetric analysis of intensity-modulated radiation therapy (IMRT) as an alternative to adjuvant high-dose-rate (HDR) brachytherapy in early endometrial cancer patients. Int J Radiat Oncol Biol Phys 2006;65:266 –273. 2. Huddart RA, Nahum A, Neal A, et al. Accuracy of pelvic radiotherapy: Prospective analysis of 90 patients in a randomised trial of blocked versus standard radiotherapy. Radiother Oncol 1996;39:19 –29. 3. Mundt AJ, Lujan AE, Rotmensch J, et al. Intensity-modulated whole pelvic radiotherapy in women with gynecologic malignancies. Int J Radiat Oncol Biol Phys 2002;52:1330 –1337. 4. Pötter R, Haie-Meder C, Limbergen E, et al. Recommendations from gynaecological (GYN) GEC ESTRO working group (II): Concepts and terms in 3D image-based treatment planning in cervix cancer brachytherapy—3D dose volume parameters and aspects of 3D image-based anatomy, radiation physics, radiobiology. Radiother Oncol 2006;78:67–77. 5. Choo JJ, Scudiere J, Bitterman P, et al. Vaginal lymphatic channel
ARNO J. MUNDT, M.D. Department of Radiation Oncology University of California San Diego La Jolla, CA doi:10.1016/j.ijrobp.2006.07.017 1. Ahamad A, Jhingran A. New radiation techniques in gynecological cancer. Int J Gynecol Cancer 2004;14:569 –579. 2. Guerrero M, Li XA, Ma L, et al. Simultaneous integrated intensitymodulated radiotherapy boost for locally advanced gynecological cancer: Radiobiological and dosimetric considerations. Int J Radiat Oncol Biol Phys 2005;62:933–939. 3. Roeske JC, Lujan A, Rotmensch J, et al. A feasibility study of IMRT for the treatment of cervical cancer patients unable to receive intracavitary brachytherapy. In: Enderle JD. Proceedings of the 22nd Annual Inter956
Letters to the editor national Conference of the IEEE, Engineering in Medicine and Biology Society, 2000, Chicago, IL. Piscataway, NJ: IEEE; 2000. p. 463– 465. 4. Wahab SH, Malyapa RS, Mutic S, et al. A treatment planning study comparing HDR and AGIMRT for cervical cancer. Med Phys 2004;31: 734 –743. 5. Molla M, Escude L, Nouet P, et al. Fractionated stereotactic radiotherapy boost for gynecologic tumors: An alternative to brachytherapy? Int J Radiat Oncol Biol Phys 2005;62:118 –124. 6. Chan P, Yeo I, Perkins G, et al. Dosimetric comparison of intensitymodulated, conformal, and four-field pelvic radiotherapy boost plans for gynecologic cancer: A retrospective planning study. Radiat Oncol 2006; 1:13.
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7. Datta NR, Basu R, Das KJ, et al. Problems in reporting doses and volumes during multiple high-dose-rate intracavitary brachytherapy for carcinoma cervix as per ICRU Report 38: A comparative study using flexible and rigid applicators. Gynecol Oncol 2003;91:285–292. 8. Garipagaoglu M, Tuncel N, Dalmaz MG, et al. Changes in applicator positions and dose distribution between high dose rate brachytherapy fractions in cervix carcinoma patients receiving definitive radiotherapy. Br J Radiol 2006;79:504 –509. 9. Aydogan B, Mundt AJ, Smith BD, et al. A dosimetric analysis of intensity-modulated radiation therapy (IMRT) as an alternative to adjuvant high-dose-rate (HDR) brachytherapy in early endometrial cancer patients. Int J Radiat Oncol Biol Phys 2006;65:266 –273.
LETTERS TO THE EDITOR BRACHYTHERAPY VS. IMRT FOR IRRADIATION OF THE VAGINAL VAULT: IN REGARD TO AYDOGAN ET AL. (INT J RADIAT ONCOL BIOL PHYS 2006;65:266 –273)
location and its implication for intracavitary brachytherapy radiation treatment. Brachytherapy 2005;4:236 –240.
To the Editor: We congratulate Aydogan et al. (1) on developing the field of intensity-modulated radiotherapy (IMRT) with their article comparing dosimetry of IMRT to high-dose-rate (HDR) brachytherapy for irradiation of the vaginal vault in endometrial cancer. However, we feel that there are still good reasons to treat with HDR brachytherapy. The beauty of vault HDR brachytherapy is that planning target volume (PTV) is essentially equivalent to clinical target volume (CTV) because the applicator is an immobilization device. Intensity-modulated RT must allow a margin for setup inaccuracies and internal organ motion; otherwise, we risk geographic miss. Standard patient immobilization for pelvic radiotherapy is accurate to 2– 4 mm compared with bony anatomy (2). Obesity, frequent in endometrial cancer, can greatly increase this. Internal organ movement of the vault has not been accurately assessed, but its proximity to the rectum and bladder makes it susceptible to movement secondary to changes in their filling. Groups introducing IMRT for pelvic radiotherapy in gynecologic cancer have expanded CTV by 1 cm to create the PTV to counter geographic miss (3). Aydogan et al. have not made any allowance for the PTV margin in this analysis. Even with a reproducible immobilization technique, PTV margin will need to be taken into account. It is these dosimetric data that will need to be planned and then compared with HDR brachytherapy dosimetry to give a realistic comparison. Aydogan modeled a 3-cm diameter applicator treating 4 cm of vagina, dosed to 0.5-cm depth. An additional 0.5-cm uncertainty margin increases PTV from 28.2 cm3 to 76.2 cm3! The article compares maximum dose points in organs at risk; however, in brachytherapy, because of the high-dose fall off and uncertainties in calculations, these are not usually considered clinically relevant (4). Instead, it may be more appropriate to compare highest dose with a contiguous area of the organs at risk (e.g., 0.1 cm3) (4). Comment is made on the dose nonuniformity of the HDR plan compared with the IMRT plan. This can be considered as a further advantage of brachytherapy over IMRT. The aim of vaginal vault irradiation is to irradiate the vaginal vault lymphatics. In 97% of cases with a stretched vagina, these occur within 3 mm of the vaginal surface (5). This area receives ⬎100% of the prescribed dose (where dose is prescribed to 0.5 cm, as is our practice) from vaginal vault brachytherapy. Therefore, for a similar dose at 0.5 cm, the vaginal vault lymphatics will receive a considerably higher dose with brachytherapy than IMRT, which may have clinical significance.
IN RESPONSE TO DRS. CAMERON AND CORNES To the Editor: There has been a great interest in intensity-modulated therapy (IMRT) as an alternative to brachytherapy in recent years (1– 6). With regard to the role of IMRT in the treatment of the vaginal vault, Drs. Cameron and Cornes raise a number of interesting and important points. We agree that IMRT requires an additional margin to account for internal motion, intrafractional uncertainties, and setup error. However, inclusion of such margin in IMRT does not necessarily result in a larger dose to the surrounding organs at risk (OAR) in comparison to brachytherapy (5). In addition, a margin may also be required for high-dose-rate (HDR) brachytherapy (7, 8). A systematic study is needed to quantify the uncertainty associated with vaginal cylinder placement because there are no published studies, to our knowledge, which investigate it. For IMRT to be successful in this disease site, it must be used in conjunction with a suitable immobilization method to reduce organ motion and setup error (9). Thus, in our study, we proposed the use of an internal immobilization system consisting of a vaginal cylinder and an indexing mechanism. Such a device may also be used to reduce intrafractional errors when it is used as surrogate in an image-guided approach. Evaluation of the internal immobilization device is under way at our institution. Vaginal vault HDR brachytherapy also has several limitations that may be overcome with IMRT. For example, the tumor volume often extends deeper in the perivaginal and parametrial tissues, particularly in women with recurrent disease. With an HDR cylinder, it is impossible to treat deeper or irregularly shaped tumors without irradiating the OAR to a much higher dose than the prescription dose. With IMRT, the dose can be sculpted to the shape of the planning target volume while minimizing the dose to surrounding normal tissue. These characteristics may allow IMRT to be used in patients who are unable to receive brachytherapy because of recurrence, irregular pelvic anatomy, medical problems, or poor tumor regression with external beam radiotherapy. In conclusion, we agree with Drs. Cameron and Cornes’ concerns on the widespread adoption of IMRT for this disease site before a rigorous clinical evaluation. However, with a suitable internal immobilization device used in conjunction with image-guided technologies, our approach may provide a comparable or better dose distribution than HDR brachytherapy. Clearly, a well-designed prospective clinical trial is needed to determine the efficacy and safety of this approach.
ALISON CAMERON PAUL CORNES, B.M.B.CH., M.R.C.P. Department of Clinical Oncology Bristol Haematology and Oncology Centre Bristol, United Kingdom
BULENT AYDOGAN, PH.D. JOHN C. ROESKE, PH.D. Department of Radiation and Cellular Oncology University of Chicago Chicago, IL
doi:10.1016/j.ijrobp.2006.07.016 1. Aydogan B, Mundt AJ, Smith BD, et al. A dosimetric analysis of intensity-modulated radiation therapy (IMRT) as an alternative to adjuvant high-dose-rate (HDR) brachytherapy in early endometrial cancer patients. Int J Radiat Oncol Biol Phys 2006;65:266 –273. 2. Huddart RA, Nahum A, Neal A, et al. Accuracy of pelvic radiotherapy: Prospective analysis of 90 patients in a randomised trial of blocked versus standard radiotherapy. Radiother Oncol 1996;39:19 –29. 3. Mundt AJ, Lujan AE, Rotmensch J, et al. Intensity-modulated whole pelvic radiotherapy in women with gynecologic malignancies. Int J Radiat Oncol Biol Phys 2002;52:1330 –1337. 4. Pötter R, Haie-Meder C, Limbergen E, et al. Recommendations from gynaecological (GYN) GEC ESTRO working group (II): Concepts and terms in 3D image-based treatment planning in cervix cancer brachytherapy—3D dose volume parameters and aspects of 3D image-based anatomy, radiation physics, radiobiology. Radiother Oncol 2006;78:67–77. 5. Choo JJ, Scudiere J, Bitterman P, et al. Vaginal lymphatic channel
ARNO J. MUNDT, M.D. Department of Radiation Oncology University of California San Diego La Jolla, CA doi:10.1016/j.ijrobp.2006.07.017 1. Ahamad A, Jhingran A. New radiation techniques in gynecological cancer. Int J Gynecol Cancer 2004;14:569 –579. 2. Guerrero M, Li XA, Ma L, et al. Simultaneous integrated intensitymodulated radiotherapy boost for locally advanced gynecological cancer: Radiobiological and dosimetric considerations. Int J Radiat Oncol Biol Phys 2005;62:933–939. 3. Roeske JC, Lujan A, Rotmensch J, et al. A feasibility study of IMRT for the treatment of cervical cancer patients unable to receive intracavitary brachytherapy. In: Enderle JD. Proceedings of the 22nd Annual Inter956
Letters to the editor national Conference of the IEEE, Engineering in Medicine and Biology Society, 2000, Chicago, IL. Piscataway, NJ: IEEE; 2000. p. 463– 465. 4. Wahab SH, Malyapa RS, Mutic S, et al. A treatment planning study comparing HDR and AGIMRT for cervical cancer. Med Phys 2004;31: 734 –743. 5. Molla M, Escude L, Nouet P, et al. Fractionated stereotactic radiotherapy boost for gynecologic tumors: An alternative to brachytherapy? Int J Radiat Oncol Biol Phys 2005;62:118 –124. 6. Chan P, Yeo I, Perkins G, et al. Dosimetric comparison of intensitymodulated, conformal, and four-field pelvic radiotherapy boost plans for gynecologic cancer: A retrospective planning study. Radiat Oncol 2006; 1:13.
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7. Datta NR, Basu R, Das KJ, et al. Problems in reporting doses and volumes during multiple high-dose-rate intracavitary brachytherapy for carcinoma cervix as per ICRU Report 38: A comparative study using flexible and rigid applicators. Gynecol Oncol 2003;91:285–292. 8. Garipagaoglu M, Tuncel N, Dalmaz MG, et al. Changes in applicator positions and dose distribution between high dose rate brachytherapy fractions in cervix carcinoma patients receiving definitive radiotherapy. Br J Radiol 2006;79:504 –509. 9. Aydogan B, Mundt AJ, Smith BD, et al. A dosimetric analysis of intensity-modulated radiation therapy (IMRT) as an alternative to adjuvant high-dose-rate (HDR) brachytherapy in early endometrial cancer patients. Int J Radiat Oncol Biol Phys 2006;65:266 –273.