In Reply to Dr. Cai et al.
1
IN REPLY TO DRS. FROEHNER AND WIRTH To the Editor: We wish to thank Dr. Froehner for his valuable comments. His statement that the rates of lung cancer are more elevated among brachy- therapy candidates than among surgical candidates is very pertinent. It is also very pertinent to suggest that controlling for age and comorbidities may in- directly eliminate some of the differences that might exist between radiother- apy patients and their radical prostatectomy counterparts. However, as his observation about brachytherapy and surgery cohorts suggests, these differ- ences might not be eliminated completely. This reasoning suggests that important differences may exist between radiotherapy and radical prostatec- tomy patients with regard to lung cancer risk. Effective elimination of such differences indeed would require a randomized trial. Since the present study did not rely on a randomized design, we do echo the cautionary words of Dr. Froehner about using caution in the interpretation of the numbers needed to harm. NAEEM BHOJANI, M.D. MAXINE SUN, B.SC. RODOLPHE THURET, M.D. LARS BUDAUS, M.D. PIERRE I. KARAKIEWICZ, M.D. Cancer Prognostics and Health Outcomes Unit University of Montreal Health Centre Montreal, Canada doi:10.1016/j.ijrobp.2010.03.052 RESPONSE TO ‘‘STANDARD AND NONSTANDARD CRANIOSPINAL RADIOTHERAPY USING HELICAL TOMOTHERAPY.’’ (INT J RADIAT ONCOL BIOL PHYS 2010;77:926–931) To the Editor: We read the study of Parker and colleagues (1) with great interest. Helical tomotherapy (HT) delivers continuous arc-based intensity- modulated radiotherapy (IMRT) that gives high conformality and excellent dose homogeneity for the target volumes. Its dosimetric advantage compared with linac-based IMRT has been reported in the treatment of head and neck cancer (2), prostate cancer (3), and other. For craniospinal irradiation (CSI), the target length is much longer than others, but the HT plan is a single method. The translational and rotational errors should be the biggest influ- encing factor to the conformality and dose homogeneity for the target vol- umes. So we doubt whether HT is an excellent tool for CSI. In the report of Parker et al. (1), all patients were immobilized by use of a standard head-and-neck thermoplastic mask, Megavoltage CT scan was performed to correct setup errors, once the patient was positioned to within 2 mm of the planned position, the treatment could proceed; once the error was more than 5 mm in any direction, the patient needed to be repositioned. But the lumbosacral portion cannot be immobilized steadily for the use of the head-and-neck thermoplastic mask, and treatment time is more than 600 sec- onds, which is always more than 900 seconds in our institute. Heteronomous movement of the lumbosacral portion will occur, and then the position may change more than 2 mm and 1 easily, resulting in different dose distribu- tions. Otherwise, from the report of Hurkmans et al. (4) and our experiences, the systematic and random setup errors for the head are less than that for the general pelvic area. It is not easy to position the patient to within 2 mm of the planned position, so many Megavoltage CT scans from head to sacrum will be performed until the position is right, which may increase the integral dose of the whole body. We have used HT to treat 21 patients requiring CSI, with a median age of 14 years (range, 4–26), total dose 19.5–30.6Gy. Grade 2 hematologic toxic- ities were observed in 12 patients and Grade 3 in 9 patients. We think the more serious hematologic toxicities should be due to HT planing with 360 delivery beam. Not only the skull and vertebral column but also the ster- num, ribs, and pelvis received an extra dose of radiation, leading to myelo- suppression. As Penagaricano et al (5) has said, the impact of a small increase in whole body integral dose was unknown, and whether the extra radiation to young patients could influence their growing development is also unknown. Moreover, we find that the study did not consider the protec- tion of the ovaries, so we surmise that all these 4 patients were male. For female patients, an HT plan cannot avoid irradiation to the ovaries; three- dimensional radiotherapy should be used to irradiate the spinal below L5. All in all, we believe that HT is a better choice for CSI, but not an ‘‘excellent’’ choice. BO-NING CAI, M.M. LIN-CHUN FENG, M.M. LIN MA, M.D., PH.D. Department of Radiation Oncology Chinese PLA General of Hospital Beijing, China doi:10.1016/j.ijrobp.2010.05.067 1. Parker W, Brodeur M, Roberge D, et al. Standard and nonstandard cranio- spinal radiotherapy using helical tomotherapy. Int J Radiat Oncol Biol Phys 2010;77:926–931. 2. Sheng K, Molloy JA, Read PW. Intensity-modulated radiation therapy (IMRT) dosimetry of the head and neck: A comparison of treatment plans using linear accelerator-based IMRT and helical tomotherapy. Int J Radiat Oncol Biol Phys 2006;65:917–923. 3. Aoyama H, Westerly DC, Mackie TR, et al. Integral radiation dose to nor- mal structures with conformal external beam radiation. Int J Radiat Oncol Biol Phys 2006;64:962–967. 4. Hurkmans CW, Remeijer P, Lebesque JV, et al. Set-up verification using portal imaging: Review of current clinical practice. Radiother Oncol 2001;58:105–120. 5. Penagaricano JA, Papanikolaou N, Yan Y, et al. Feasibility of cranio- spinal axis radiation with the Hi-Art tomotherapy system. Radiother Oncol 2005;76:72–78. IN REPLY TO DR. CAI ET AL. To the Editor: We appreciate the opportunity to respond to the important issues raised by Dr. Cai and colleagues regarding our recent publication. Regarding setup uncertainties, we use a thermoplastic head-and-neck mask for immobilization and are usually able to set up the patients to within the limits of the planning target volume (PTV) margin. This is verified for every patient at every fraction using Mega Voltage Computed Tomography (MVCT) imaging of the entire PTV volume. As for intrafraction movement, the majority of our patients are young children, who are anesthetized for treatment. We define the PTV margin depending on whether the patient is a child (3 mm) or an adult (5 mm). If the treatment team thinks the patient is restless or moving during treatment, an MVCT is taken immediately for verification. The PTV margin could be expanded accordingly, although in practice this has not been necessary in any case. Cai et al. suggest that protection of the ovaries should be an important con- sideration, and we agree. The cases shown include only 1 female patient in whom we did not consider ovary sparing because the patient had previously received treatment. Our current practice is to identify the ovaries on the plan- ning CT scan and attempt to spare them to a dose less than 2 Gy if appropriate in the clinical situation. For the cases in which we have considered the ovaries, we have had no difficulty sparing them to doses less than 2 Gy because they have lain at or below the inferior limit of the PTV. Even if the ovaries were to be above the inferior limit of the PTV, we believe that sparing to this dose level would be possible for children treated with prescription doses below 23.4 Gy. In our experience, hematologic toxicity is not greater that seen with other craniospinal techniques. We have recently published our results for patients treated in the supine position (1), 2 of whom were treated with tomotherapy. Since then we have treated a total of 30 patients with CSI on tomotherapy. We have not had to interrupt CSI in any case, and all patients have gone on to receive chemotherapy as planned. WILLIAM PARKER, M.SC. CAROLYN FREEMAN, M.B.B.S. Departments of Medical Physics and Radiation Oncology McGill University Health Centre Montreal, Quebec Canada doi:10.1016/j.ijrobp.2010.05.068 1. Huang F, Parker W, Freeman CR. Feasibility and early outcomes of supine-position craniospinal irradiation. Pediatr Blood Cancer 2010;54: 322–325. 1280 I. J. Radiation Oncology d Biology d Physics Volume 78, Number 4, 2010
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Transcript of In Reply to Dr. Cai et al.
1280 I. J. Radiation Oncology d Biology d Physics Volume 78, Number 4, 2010
IN REPLY TO DRS. FROEHNER AND WIRTH
To the Editor: We wish to thank Dr. Froehner for his valuable comments.His statement that the rates of lung cancer are more elevated among brachy-therapy candidates than among surgical candidates is very pertinent. It is alsovery pertinent to suggest that controlling for age and comorbidities may in-directly eliminate some of the differences that might exist between radiother-apy patients and their radical prostatectomy counterparts. However, as hisobservation about brachytherapy and surgery cohorts suggests, these differ-ences might not be eliminated completely. This reasoning suggests thatimportant differences may exist between radiotherapy and radical prostatec-tomy patients with regard to lung cancer risk. Effective elimination of suchdifferences indeed would require a randomized trial. Since the present studydid not rely on a randomized design, we do echo the cautionary words ofDr. Froehner about using caution in the interpretation of the numbers neededto harm.
NAEEM BHOJANI, M.D.MAXINE SUN, B.SC.RODOLPHE THURET, M.D.LARS BUDAUS, M.D.PIERRE I. KARAKIEWICZ, M.D.Cancer Prognostics and Health Outcomes UnitUniversity of Montreal Health CentreMontreal, Canada
doi:10.1016/j.ijrobp.2010.03.052
RESPONSE TO ‘‘STANDARD AND NONSTANDARD
CRANIOSPINAL RADIOTHERAPY USING HELICAL
TOMOTHERAPY.’’ (INT J RADIAT ONCOL BIOLPHYS 2010;77:926–931)
To the Editor: We read the study of Parker and colleagues (1) with greatinterest. Helical tomotherapy (HT) delivers continuous arc-based intensity-modulated radiotherapy (IMRT) that gives high conformality and excellentdose homogeneity for the target volumes. Its dosimetric advantage comparedwith linac-based IMRT has been reported in the treatment of head and neckcancer (2), prostate cancer (3), and other. For craniospinal irradiation (CSI),the target length is much longer than others, but the HT plan is a singlemethod. The translational and rotational errors should be the biggest influ-encing factor to the conformality and dose homogeneity for the target vol-umes. So we doubt whether HT is an excellent tool for CSI. In the reportof Parker et al. (1), all patients were immobilized by use of a standardhead-and-neck thermoplastic mask, Megavoltage CT scan was performedto correct setup errors, once the patient was positioned to within 2 mm ofthe planned position, the treatment could proceed; once the error was morethan 5 mm in any direction, the patient needed to be repositioned. But thelumbosacral portion cannot be immobilized steadily for the use of thehead-and-neck thermoplastic mask, and treatment time is more than 600 sec-onds, which is always more than 900 seconds in our institute. Heteronomousmovement of the lumbosacral portion will occur, and then the position maychange more than 2 mm and 1� easily, resulting in different dose distribu-tions. Otherwise, from the report of Hurkmans et al. (4) and our experiences,the systematic and random setup errors for the head are less than that for thegeneral pelvic area. It is not easy to position the patient to within 2 mm of theplanned position, so many Megavoltage CT scans from head to sacrum willbe performed until the position is right, which may increase the integral doseof the whole body.
We have used HT to treat 21 patients requiring CSI, with a median age of14 years (range, 4–26), total dose 19.5–30.6Gy. Grade 2 hematologic toxic-ities were observed in 12 patients and Grade 3 in 9 patients. We think themore serious hematologic toxicities should be due to HT planing with360� delivery beam. Not only the skull and vertebral column but also the ster-num, ribs, and pelvis received an extra dose of radiation, leading to myelo-suppression. As Penagaricano et al (5) has said, the impact of a smallincrease in whole body integral dose was unknown, and whether the extraradiation to young patients could influence their growing development isalso unknown. Moreover, we find that the study did not consider the protec-tion of the ovaries, so we surmise that all these 4 patients were male. Forfemale patients, an HT plan cannot avoid irradiation to the ovaries; three-dimensional radiotherapy should be used to irradiate the spinal below L5.
All in all, we believe that HT is a better choice for CSI, but not an ‘‘excellent’’choice.
BO-NING CAI, M.M.LIN-CHUN FENG, M.M.LIN MA, M.D., PH.D.Department of Radiation OncologyChinese PLA General of HospitalBeijing, China
doi:10.1016/j.ijrobp.2010.05.067
1. Parker W, Brodeur M, Roberge D, et al. Standard and nonstandard cranio-spinal radiotherapy using helical tomotherapy. Int J Radiat Oncol BiolPhys 2010;77:926–931.
2. Sheng K, Molloy JA, Read PW. Intensity-modulated radiation therapy(IMRT) dosimetry of the head and neck: A comparison of treatment plansusing linear accelerator-based IMRT and helical tomotherapy. Int J RadiatOncol Biol Phys 2006;65:917–923.
3. Aoyama H, Westerly DC, Mackie TR, et al. Integral radiation dose to nor-mal structures with conformal external beam radiation. Int J Radiat OncolBiol Phys 2006;64:962–967.
4. Hurkmans CW, Remeijer P, Lebesque JV, et al. Set-up verification usingportal imaging: Review of current clinical practice. Radiother Oncol2001;58:105–120.
5. Penagaricano JA, Papanikolaou N, Yan Y, et al. Feasibility of cranio-spinal axis radiation with the Hi-Art tomotherapy system. RadiotherOncol 2005;76:72–78.
IN REPLY TO DR. CAI ET AL.
To the Editor: We appreciate the opportunity to respond to the importantissues raised by Dr. Cai and colleagues regarding our recent publication.
Regarding setup uncertainties, we use a thermoplastic head-and-neckmask for immobilization and are usually able to set up the patients to withinthe limits of the planning target volume (PTV) margin. This is verified forevery patient at every fraction using Mega Voltage Computed Tomography(MVCT) imaging of the entire PTV volume. As for intrafraction movement,the majority of our patients are young children, who are anesthetized fortreatment. We define the PTV margin depending on whether the patient isa child (3 mm) or an adult (5 mm). If the treatment team thinks the patientis restless or moving during treatment, an MVCT is taken immediately forverification. The PTV margin could be expanded accordingly, although inpractice this has not been necessary in any case.
Cai et al. suggest that protection of the ovaries should be an important con-sideration, and we agree. The cases shown include only 1 female patient inwhom we did not consider ovary sparing because the patient had previouslyreceived treatment. Our current practice is to identify the ovaries on the plan-ning CT scan and attempt to spare them to a dose less than 2 Gy if appropriatein the clinical situation. For the cases in which we have considered the ovaries,we have had no difficulty sparing them to doses less than 2 Gy because theyhave lain at or below the inferior limit of the PTV. Even if the ovaries were tobe above the inferior limit of the PTV, we believe that sparing to this dose levelwould be possible for children treated with prescription doses below 23.4 Gy.
In our experience, hematologic toxicity is not greater that seen with othercraniospinal techniques. We have recently published our results for patientstreated in the supine position (1), 2 of whom were treated with tomotherapy.Since then we have treated a total of 30 patients with CSI on tomotherapy.We have not had to interrupt CSI in any case, and all patients have goneon to receive chemotherapy as planned.
WILLIAM PARKER, M.SC.CAROLYN FREEMAN, M.B.B.S.Departments of Medical Physics and Radiation OncologyMcGill University Health CentreMontreal, QuebecCanada
doi:10.1016/j.ijrobp.2010.05.068
1. Huang F, Parker W, Freeman CR. Feasibility and early outcomes ofsupine-position craniospinal irradiation. Pediatr Blood Cancer 2010;54:322–325.
