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Table of Contents
LETTER TO EDITOR
Year : 2019  |  Volume : 2  |  Issue : 1  |  Page : 129-130

Hypothyroidism in head and neck cancer: A surrogate of better radiation delivery?


Department of Radiation Oncology, Kokilaben Dhirubhai Ambani Hospital, Mumbai, Maharashtra, India

Date of Web Publication9-Sep-2019

Correspondence Address:
Kaustav Talapatra
Department of Radiation Oncology, Kokilaben Dhirubhai Ambani Hospital, Andheri, Mumbai - 400 053, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/CRST.CRST_30_19

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How to cite this article:
Talapatra K, Vadgaonkar RA. Hypothyroidism in head and neck cancer: A surrogate of better radiation delivery?. Cancer Res Stat Treat 2019;2:129-30

How to cite this URL:
Talapatra K, Vadgaonkar RA. Hypothyroidism in head and neck cancer: A surrogate of better radiation delivery?. Cancer Res Stat Treat [serial online] 2019 [cited 2019 Nov 21];2:129-30. Available from: http://www.crstonline.com/text.asp?2019/2/1/129/266452



Dear Editor,

We congratulate Dr. Patil et al. for their efforts to estimate a relationship between treatment-induced hypothyroidism and improvement in clinical outcomes.[1] Prospective design of the study and evaluation of clinically meaningful outcomes adds immense value to their observations. We also appreciate Dr. Puri's editorial on the subject.[2] He raised certain pertinent questions that further increased interest in treatment-induced hypothyroidism.

The work by Patil et al. brought a new insight into an old unanswered question from the radiation oncologist's perspective. It has been previously estimated that external beam radiotherapy to the neck region is associated with the development of treatment-induced hypothyroidism, and dthe dose-volume relationship has been established.[3] Mean thyroid dose of ≥30 Gy was significantly associated with the development of hypothyroidism.[3] In the study by Patil et al., more than three-fourths of the patients had oral cavity cancer and three-fourth had locoregionally advanced disease.[1] In locoregionally advanced oral cavity cancer patients, lower cervical neck levels need to be irradiated with a dose sufficient to sterilize microscopic cancer cells. Hence, cervical levels III and IV inadvertently end up receiving more than 40 Gy (2 Gy equivalent) dose. Considering the margin for setup errors and internal motion, the thyroid gland also receives a significant amount of prescription dose. Hence, adequacy of radiotherapy leading to hypothyroidism appears to be a surrogate marker for improved outcomes.

However, Patil et al. also correctly pointed out the beneficial effect of hypothyroidism in other non-head and neck solid tumors.[1] Various mechanisms are proposed to explain the favorable response in these tumors. Physiological dependency of glial cells leading to arrest in growth with the development of hypothyroidism is well reported in the literature.[4] Biochemical and clinical hypothyroidism in patients receiving tyrosine kinase inhibitors is a consistent finding observed in patients with renal cell carcinoma and gastrointestinal stromal tumors.[5] Sunitinib and other vascular endothelial growth factor (VEGF) inhibitors may lead to inhibition of binding of VEGF to thyroid cells leading to inhibition of thyroxine production.

Hence, improved outcomes in head and neck cancer patients with the development of treatment-induced hypothyroidism may appear to be the associated additive effect of better radiation delivery as well as other non-radiotherapy-dependent mechanisms.

It is proposed that the current/ future studies may do dosimetric evaluation of the radiation plan and assess whether thyroid was adequately spared. It will also be interesting to note the dose correlation/ dose received by the thyroid in patients who had improved outcomes. These key points may form the basis for future studies.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
Patil VM, Noronha V, Joshi A, Mandal TK, Bhattacharjee A, Goel A, et al. Hypothyroidism post-chemoradiation on outcomes in head-and-neck cancer. Cancer Res Stat Treat 2018;1:84-91.  Back to cited text no. 1
  [Full text]  
2.
Puri T. Treatment-induced hypothyroidism in head-and-neck cancer – Is it a crystal ball? Cancer Res Stat Treat 2018;1:118-20.  Back to cited text no. 2
  [Full text]  
3.
Fujiwara M, Kamikonya N, Odawara S, Suzuki H, Niwa Y, Takada Y, et al. The threshold of hypothyroidism after radiation therapy for head and neck cancer: A retrospective analysis of 116 cases. J Radiat Res 2015;56:577-82.  Back to cited text no. 3
    
4.
Davis FB, Tang HY, Shih A, Keating T, Lansing L, Hercbergs A, et al. Acting via a cell surface receptor, thyroid hormone is a growth factor for glioma cells. Cancer Res 2006;66:7270-5.  Back to cited text no. 4
    
5.
Schoeffski P, Wolter P, Himpe U, Dychter SS, Baum CM, Prenen H. et al. Sunitinib related thyroid dysfunction: A single-center retrospective and prospective evaluation. J Clin Oncol 2006;24:3092.  Back to cited text no. 5
    




 

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