MARGINAL MISSES AFTER POSTOPERATIVE
1
estimate of g 50 from the randomized trials becomes 0.78 (0.46–1.09) in- stead of 0.84. Dr. Williams’ second, more speculative proposition, that an- drogen deprivation therapy (ADT) affects the steepness, not just the position, of the radiation dose–response curve, is not supported by the intermediate-high risk data (Fig. 1). The p value for heterogeneity among trials is 0.05, mainly because of the high g 50 -estimate from Kuban’s trial, with no obvious trend from Zietman (0% ADT) via Peeters (21% ADT) to Dearnaley (100% ADT). Low-risk patient g-estimates are more uncertain and we do not feel that any reasonable inference can be made regarding g 50 and ADT. IVAN R. VOGELIUS,PH.D. Department of Oncology Rigshospitalet, University of Copenhagen Denmark SøREN M. BENTZEN,PH.D., D.SC. Department of Human Oncology University of Wisconsin School of Medicine and Public Health K4/316 Clinical Science Center 600 Highland Avenue Madison, WI doi:10.1016/j.ijrobp.2010.12.010 MARGINAL MISSES AFTER POSTOPERATIVE INTENSITY-MODULATED RADIOTHERAPY FOR HEAD AND NECK CANCER: IN REGARD TO CHEN ET AL. (INT J RADIAT ONCOL BIOL PHYS. 2010 JUL 23) To the Editor: We read with interest the report by Chen and colleagues addressing the rate of marginal misses after postoperative intensity- modulated radiotherapy (IMRT) for head-and-neck cancer (1). The pri- mary endpoint was the incidence of geographical ‘‘marginal-field’’ misses expressed by the incidence of postoperative locoregional (LR) failure in disease control. While we acknowledge the importance of the proposed re- search question, we feel that the study design and subsequent conclusions were rather inaccurate. First, the authors state that positron emission tomography (PET) scans were ordered in only 20 patients (22%) before treatment. It is not clear, how- ever, if PET scans were available and/or used retrospectively in the 6 pa- tients under question to assess the adequacy of initial radiation dose coverage. LR recurrences picked up by follow-up PET scans might actually represent failure in original target volume coverage rather than technique related ‘‘marginal’’ miss. Technically, the authors failed to specify the average margin of organ de- viation following the described ‘‘formal’’ coregistration of radiological follow-up images of tumor recurrence with the computed tomography (CT) images used in radiotherapy planning. This is of paramount impor- tance since migration of only a few millimeters might mistakably describe an in-fieldfailure as a ‘‘marginal’’ miss. IMRT plans are characterized by dramatic dose gradients. In this re- port, Chen and colleagues test the deleterious effects of steep dose fall- offs rather than the adequacy of guideline clinical target volume (CTV) volumes. However, ‘‘marginal’’ misses were defined in accordance to the CTV. Relating the geographical distribution of LR recurrence to the 95% isodose line would poses as a more valid alternative and has been previously narrated by Eisbruch et al. (2) in their report regarding recurrences near the base of skull after IMRT for head-and-neck cancer. Furthermore, the authors specifically state that the contoured CTV and consequently the resultant treatment volume were inadequate in one of the clinical cases described in Figure 2. In this patient, LR treatment failure might represent plan inadequacy rather than technique-related "marginal" miss. Similarly, intraoperative tumor spillage and seedling pose as possible explanations for the two cases of dermal/subcutaneous recurrence. Chen et al. came short from laying down this perfectly reasoned scenario. All previously described study design deviancies markedly influence the reported conclusions. We believe that more meticulous assessments of the spatial distribution of LR recurrences are needed to assess the safety IMRT in head-and-neck cancers. AHMED SALEM, M.D. ABDULLA AL-RASHDAN, M.D. FAWZI ABU-HIJLE, M.D. JAMAL KHADER, M.D. SAMEH HASHEM, M.D. ABDELATIEF ALMOUSA, M.D., PH.D. Department of Radiation Oncology King Hussein Cancer Center Amman, Jordan doi:10.1016/j.ijrobp.2011.01.026 1. Chen AM, Farwell DG, Luu Q, et al. Marginal misses after postoperative intensity-modulated radiotherapy for head and neck cancer. Int J Radiat Oncol Biol Phys 2010. In press. 2. Eisbruch A, Marsh LH, Dawson LA, et al. Recurrences near base of skull after IMRT for head-and-neck cancer: implications for target delineation in high neck and for parotid gland sparing. Int J Radiat Oncol Biol Phys 2004;59:28–42. IN REPLY TO SALEM ET AL. To the Editor: We thank Dr. Salem and colleagues for their thoughtful comments regarding our work and agree that retrospective limitations make drawing definitive conclusions difficult. What must be kept in mind, however, is that our study was designed not to determine the true incidence of geographic miss after postoperative intensity-modulated radiotherapy (IMRT) for head-and-neck cancer, but rather to serve as an illustrative series of cases documenting potential spatial patterns of failures. As stated in the purpose of the abstract, our objectivewas to ‘‘describe’’ the location of re- currences, with the goal of promoting continual assessment with respect to how target volumes are delineated. By no means was this an exact science, inasmuch as theword ‘‘marginal’’ by its very definition implies an arbitrar- iness and uncertainty that convey a degree of subjectivity inherent in any analysis of this nature. Indeed, definitions of ‘‘marginal’’ in the setting of IMRT vary across studies (1–3). Complicating this matter is that registration methods are far from perfect, because postirradiation scans are frequently obtained with the head and neck in a different position than at the time of simulation and treatment (4, 5). Although one can argue that the ‘‘recurrences’’ we observed may have been due to persistent disease, because positron emission tomography was not routinely performed preoperatively during the time span of the study, the fact that computed tomography failed to demonstrate any abnormalities in these regions suggests that coverage of areas at risk for disease were likely adequate. Clearly, additional studies investigating patterns of failure after IMRT for head-and-neck cancer are needed to validate our conclusions that this technology can safely be applied in the postoperative setting. ALLEN M. CHEN, M.D. JAMES A. PURDY ,PH.D. University of California Davis Cancer Center Davis, CA doi:10.1016/j.ijrobp.2011.01.031 1. Eisbruch A, Marsh LH, Dawson LA, et al. Recurrences near base of skull after IMRT for head-and-neck cancer: Implications for target delineation in high neck and for parotid sparing. Int J Radiat Oncol Biol Phys 2004; 59:28–42. 2. Chao KS, Wippold FJ, Ozyigit G, et al. Determination and delineation of nodal target volumes for head-and-neck cancer based on patterns of fail- ure in patients receiving definitive and postoperative IMRT. Int J Radiat Oncol Biol Phys 2002;53:1173–1184. 3. Sanguineti G, Gunn GB, Endres EJ, et al. Patterns of locoregional failure after exclusive IMRT for oropharyngeal carcinoma. Int J Radiat Oncol Biol Phys 2008;72:737–746. 4. Hwang AB, Bacharach SL, Yom SS, et al. Can PET/computed tomogra- phy acquired in a nontreatment position be accurately registered to a head-and-neck radiotherapy planning CT? Int J Radiat Oncol Biol Phys 2009;73:578–584. 5. Ireland RH, Dyker KE, Barber DC, et al. Nonrigid image registration for head and neck cancer radiotherapy treatment planning with PET/CT. Int J Radiat Oncol Biol Phys 2007;68:952–957. 640 I. J. Radiation Oncology d Biology d Physics Volume 80, Number 2, 2011
-
Upload
jordan-medics -
Category
Documents
-
view
215 -
download
1
description
AHMED SALEM, M.D. ABDULLA AL-RASHDAN, M.D. FAWZI ABU-HIJLE, M.D. JAMAL KHADER, M.D. SAMEH HASHEM, M.D. ABDELATIEF ALMOUSA, M.D., PH.D. Department of Radiation Oncology King Hussein Cancer Center Amman, Jordan MARGINAL MISSES AFTER POSTOPERATIVE
Transcript of MARGINAL MISSES AFTER POSTOPERATIVE
640 I. J. Radiation Oncology d Biology d Physics Volume 80, Number 2, 2011
estimate of g50 from the randomized trials becomes 0.78 (0.46–1.09) in-stead of 0.84. Dr. Williams’ second, more speculative proposition, that an-drogen deprivation therapy (ADT) affects the steepness, not just theposition, of the radiation dose–response curve, is not supported by theintermediate-high risk data (Fig. 1). The p value for heterogeneity amongtrials is 0.05, mainly because of the high g50-estimate from Kuban’s trial,with no obvious trend from Zietman (0% ADT) via Peeters (21% ADT)to Dearnaley (100%ADT). Low-risk patient g-estimates are more uncertainand we do not feel that any reasonable inference can be made regarding g50and ADT.
IVAN R. VOGELIUS, PH.D.Department of OncologyRigshospitalet, University of CopenhagenDenmark
SøREN M. BENTZEN, PH.D., D.SC.Department of Human OncologyUniversity of Wisconsin School of Medicine and Public HealthK4/316 Clinical Science Center600 Highland AvenueMadison, WI
doi:10.1016/j.ijrobp.2010.12.010
MARGINAL MISSES AFTER POSTOPERATIVEINTENSITY-MODULATED RADIOTHERAPY
FOR HEAD AND NECK CANCER: IN REGARDTO CHEN ET AL. (INT J RADIAT ONCOL
BIOL PHYS. 2010 JUL 23)
To the Editor: We read with interest the report by Chen and colleaguesaddressing the rate of marginal misses after postoperative intensity-modulated radiotherapy (IMRT) for head-and-neck cancer (1). The pri-mary endpoint was the incidence of geographical ‘‘marginal-field’’ missesexpressed by the incidence of postoperative locoregional (LR) failure indisease control. While we acknowledge the importance of the proposed re-search question, we feel that the study design and subsequent conclusionswere rather inaccurate.
First, the authors state that positron emission tomography (PET) scanswere ordered in only 20 patients (22%) before treatment. It is not clear, how-ever, if PET scans were available and/or used retrospectively in the 6 pa-tients under question to assess the adequacy of initial radiation dosecoverage. LR recurrences picked up by follow-up PET scans might actuallyrepresent failure in original target volume coverage rather than techniquerelated ‘‘marginal’’ miss.
Technically, the authors failed to specify the average margin of organ de-viation following the described ‘‘formal’’ coregistration of radiologicalfollow-up images of tumor recurrence with the computed tomography(CT) images used in radiotherapy planning. This is of paramount impor-tance since migration of only a few millimeters might mistakably describean in-field failure as a ‘‘marginal’’ miss.
IMRT plans are characterized by dramatic dose gradients. In this re-port, Chen and colleagues test the deleterious effects of steep dose fall-offs rather than the adequacy of guideline clinical target volume (CTV)volumes. However, ‘‘marginal’’ misses were defined in accordance tothe CTV. Relating the geographical distribution of LR recurrence tothe 95% isodose line would poses as a more valid alternative and hasbeen previously narrated by Eisbruch et al. (2) in their report regardingrecurrences near the base of skull after IMRT for head-and-neck cancer.Furthermore, the authors specifically state that the contoured CTV andconsequently the resultant treatment volume were inadequate in oneof the clinical cases described in Figure 2. In this patient, LR treatmentfailure might represent plan inadequacy rather than technique-related"marginal" miss. Similarly, intraoperative tumor spillage and seedlingpose as possible explanations for the two cases of dermal/subcutaneousrecurrence. Chen et al. came short from laying down this perfectlyreasoned scenario.
All previously described study design deviancies markedly influence thereported conclusions. We believe that more meticulous assessments of thespatial distribution of LR recurrences are needed to assess the safetyIMRT in head-and-neck cancers.
AHMED SALEM, M.D.ABDULLA AL-RASHDAN, M.D.FAWZI ABU-HIJLE, M.D.JAMAL KHADER, M.D.SAMEH HASHEM, M.D.ABDELATIEF ALMOUSA, M.D., PH.D.Department of Radiation OncologyKing Hussein Cancer CenterAmman, Jordan
doi:10.1016/j.ijrobp.2011.01.026
1. Chen AM, Farwell DG, Luu Q, et al. Marginal misses after postoperativeintensity-modulated radiotherapy for head and neck cancer. Int J RadiatOncol Biol Phys 2010. In press.
2. Eisbruch A, Marsh LH, Dawson LA, et al. Recurrences near base of skullafter IMRT for head-and-neck cancer: implications for target delineationin high neck and for parotid gland sparing. Int J Radiat Oncol Biol Phys2004;59:28–42.
IN REPLY TO SALEM ET AL.
To the Editor: We thank Dr. Salem and colleagues for their thoughtfulcomments regarding our work and agree that retrospective limitationsmake drawing definitive conclusions difficult. What must be kept in mind,however, is that our study was designed not to determine the true incidenceof geographic miss after postoperative intensity-modulated radiotherapy(IMRT) for head-and-neck cancer, but rather to serve as an illustrative seriesof cases documenting potential spatial patterns of failures. As stated in thepurpose of the abstract, our objective was to ‘‘describe’’ the location of re-currences, with the goal of promoting continual assessment with respect tohow target volumes are delineated. By no means was this an exact science,inasmuch as the word ‘‘marginal’’ by its very definition implies an arbitrar-iness and uncertainty that convey a degree of subjectivity inherent in anyanalysis of this nature. Indeed, definitions of ‘‘marginal’’ in the setting ofIMRT vary across studies (1–3). Complicating this matter is thatregistration methods are far from perfect, because postirradiation scansare frequently obtained with the head and neck in a different position thanat the time of simulation and treatment (4, 5). Although one can arguethat the ‘‘recurrences’’ we observed may have been due to persistentdisease, because positron emission tomography was not routinelyperformed preoperatively during the time span of the study, the fact thatcomputed tomography failed to demonstrate any abnormalities in theseregions suggests that coverage of areas at risk for disease were likelyadequate. Clearly, additional studies investigating patterns of failure afterIMRT for head-and-neck cancer are needed to validate our conclusionsthat this technology can safely be applied in the postoperative setting.
ALLEN M. CHEN, M.D.JAMES A. PURDY, PH.D.University of CaliforniaDavis Cancer CenterDavis, CA
doi:10.1016/j.ijrobp.2011.01.031
1. Eisbruch A, Marsh LH, Dawson LA, et al. Recurrences near base of skullafter IMRT for head-and-neck cancer: Implications for target delineationin high neck and for parotid sparing. Int J Radiat Oncol Biol Phys 2004;59:28–42.
2. Chao KS, Wippold FJ, Ozyigit G, et al. Determination and delineation ofnodal target volumes for head-and-neck cancer based on patterns of fail-ure in patients receiving definitive and postoperative IMRT. Int J RadiatOncol Biol Phys 2002;53:1173–1184.
3. Sanguineti G, Gunn GB, Endres EJ, et al. Patterns of locoregional failureafter exclusive IMRT for oropharyngeal carcinoma. Int J Radiat OncolBiol Phys 2008;72:737–746.
4. Hwang AB, Bacharach SL, Yom SS, et al. Can PET/computed tomogra-phy acquired in a nontreatment position be accurately registered toa head-and-neck radiotherapy planning CT? Int J Radiat Oncol BiolPhys 2009;73:578–584.
5. Ireland RH, Dyker KE, Barber DC, et al. Nonrigid image registration forhead and neck cancer radiotherapy treatment planningwith PET/CT. Int JRadiat Oncol Biol Phys 2007;68:952–957.
