|LETTER TO THE EDITOR
|Year : 2015 | Volume
| Issue : 2 | Page : 495-496
Carotid sparing intensity-modulated radiotherapy in early glottic cancers: A case of Maslow's hammer?
Santam Chakraborty, Geetha Muttath
Department of Radiation Oncology, Malabar Cancer Centrer, Thalassery, Kannur, Kerala, India
|Date of Web Publication||7-Jul-2015|
Department of Radiation Oncology, Malabar Cancer Centre, Thalassery, Kannur 670 103, Kerala
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Chakraborty S, Muttath G. Carotid sparing intensity-modulated radiotherapy in early glottic cancers: A case of Maslow's hammer?. J Can Res Ther 2015;11:495-6
|How to cite this URL:|
Chakraborty S, Muttath G. Carotid sparing intensity-modulated radiotherapy in early glottic cancers: A case of Maslow's hammer?. J Can Res Ther [serial online] 2015 [cited 2020 Jul 10];11:495-6. Available from: http://www.cancerjournal.net/text.asp?2015/11/2/495/139607
We read with interest the article by Chatterjee et al. who have demonstrated that helical tomotherapy can be used to delivery carotid sparing intensity-modulated radiotherapy (IMRT) in early glottic cancers (EGC).  The authors have stated that previous works done with carotid sparing IMRT have not used hypofractionated radiotherapy. It is unclear however as to how the choice of a dose schedule can impact the conformality obtained by using IMRT. Surely the authors would acknowledge that relative dosimetric sparing for the carotid vessels would similar irrespective of the prescription dose. In this regard final dose prescribed would impact the absolute dose delivered to the vessels and not the relative sparing obtained.
The exact magnitude of risk of stroke after curative intent radiotherapy for EGC remains unknown. In the study by Smith [TAG:2][/TAG:2]
et al. 4.9% of the 146 patients treated for laryngeal cancers developed an ischemic stroke.  In the pooled analysis by Scott et al. the crude risk of developing an ischemic stroke was 2.9% in irradiated patients. 
It is also unclear as to what extent co-morbidities and addiction patterns influence the risk of developing an ischemic stroke in these patients. Interestingly in a recent analysis of Surveillance Epidemiology and end results data by Hong et al. showed no difference in the risk of cerebrovascular disease in EGC patients treated with radiotherapy or surgery.  Given the above data it is easily that although radiotherapy may increase the risk of cerebrovascular accident, the absolute magnitude of the increase is undoubtedly minimal.
The authors have demonstrated mean doses to the carotid vessels to be in the range of 15-16 Gy using IMRT. Dorth et al. have demonstrated that the hazard ratio for carotid artery stenosis was 1.4 for every 10 Gy increase in mean dose to carotid bulb. Hence even this dose may not be safe. 
Intrafractional laryngeal motion during deglutination is another unaddressed area in the present manuscript. This motion of less concern in conventional techniques due to the short time of radiation involved. However, in IMRT especially with helical tomotherapy the prolonged treatment time along with the effect of interplay of leaf motion can result in significant changes in instantaneous target dosage. The authors have not modeled the impact of motion on the target dose delivery nor reported the delivery time in this paper.
It is also unclear as to why the planning target volume (PTV) was trimmed from the carotid arteries. As the PTV is a margin given to account for setup inaccuracies and organ motion is it going to be reduced in the vicinity of the carotid arteries.
Use of expensive technology like helical tomotherapy in patients of EGC for such uncertain clinical gains appears to be unwarranted especially when such excellent results can be obtained by conventional radiotherapy in a cost effective fashion.
| > References|| |
Chatterjee S, Guha S, Prasath S, Mallick I, Achari R. Carotid sparing hypofractionated tomotherapy in early glottic cancers: Refining image guided IMRT to improve morbidity. J Cancer Res Ther 2013;9:452-5.
Smith GL, Smith BD, Buchholz TA, Giordano SH, Garden AS, Woodward WA, et al
. Cerebrovascular disease risk in older head and neck cancer patients after radiotherapy. J Clin Oncol 2008;26:5119-25.
Scott AS, Parr LA, Johnstone PA. Risk of cerebrovascular events after neck and supraclavicular radiotherapy: A systematic review. Radiother Oncol 2009;90:163-5.
Hong JC, Kruser TJ, Gondi V, Mohindra P, Cannon DM, Harari PM, et al
. Risk of cerebrovascular events in elderly patients after radiation therapy versus surgery for early-stage glottic cancer. Int J Radiat Oncol Biol Phys 2013;87:290-6.
Dorth JA, Patel PR, Broadwater G, Brizel DM. Incidence and risk factors of significant carotid artery stenosis in asymptomatic survivors of head and neck cancer after radiotherapy. Head Neck 2014;36:215-9.