Correlative study of dose to thyroid and incidence of subsequent dysfunction after head and neck radiation

Ling, Stella; Bhatt, Aashish D.; Brown, Nicole V.; Nguyen, Phuong; Sipos, Jennifer A.; Chakravarti, Arnab; Rong, Yi

doi:10.1002/hed.24643

Cited by 30 publications

(52 citation statements)

References 34 publications

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“…Studies have investigated the risk factors for RT-related HT in NPC patients, and reported similar results as our univariate analysis, including female sex, 11 younger age, 12 smaller pretreatment thyroid-gland volume, 13,14 high mean radiation dose, 4,15 and high minimum radiation dose. 7 Taking the relatively high correlation among mean radiation dose, minimum radiation dose, and DVH parameters into account, we did not include a mean radiation dose or minimum radiation dose into the multivariate analysis, and found the combined DVH constraints to be independent prognostic factors for HT.…”

Section: Discussionsupporting

confidence: 80%

Thyroid dose‐volume thresholds for the risk of radiation‐related hypothyroidism in nasopharyngeal carcinoma treated with intensity‐modulated radiotherapy—A single‐institution study

Huang

Tan²,

Guo

et al. 2019

Cancer Medicine

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BackgroundTo identify thyroid dose‐volume thresholds for radiotherapy (RT)‐related hypothyroidism (HT) in patients with nasopharyngeal carcinoma (NPC) treated with intensity‐modulated RT (IMRT). In this way, we desired to guide the design of treatment plans and, finally, lower HT prevalence.MethodsIn total, 345 NPC patients treated with IMRT were evaluated retrospectively during a median follow‐up of 45.2 (range, 11.3‐64.9) months. Serum‐based assessments of thyroid function before and after IMRT were monitored periodically. Thyroid dose‐volume parameters were analyzed for their association with HT risk.ResultsIn total, 44.1% of patients (152/345) developed primary HT. Analyses of thyroid dose‐volume parameters identified a stringent dose‐volume histogram (DVH) threshold defined by V 25Gy (the percentage thyroid volume that receives >25 Gy, not the absolute volume) ≤60%, V 35Gy ≤ 55%, and V 45Gy ≤ 45%. Patients whose thyroid DVHs satisfied these constraints had a lower prevalence of 2‐year HT compared with the overall prevalence (13.2% vs 25.8%, P < .001). Another DVH was defined by V 25Gy > 95%, V 35Gy > 90%, and V 45Gy > 75%, and patients whose thyroid DVHs satisfied with these constraints had a higher prevalence of 2‐year HT than the overall incidence (36.0% vs 25.8%, P < .001).ConclusionWe recommend V 25Gy ≤ 60%, V 35Gy ≤ 55%, and V 45Gy ≤ 45% as the “stringent” DVH line, and V 25Gy > 95%, V 35Gy > 90%, and V 45Gy > 75% as the “inhibition” DVH line, under the precondition of not compromising the target coverage. These findings could help in the design of individual treatment plans and, eventually, to lowering of HT prevalence.

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Section: Discussionsupporting

confidence: 80%

Thyroid dose‐volume thresholds for the risk of radiation‐related hypothyroidism in nasopharyngeal carcinoma treated with intensity‐modulated radiotherapy—A single‐institution study

Huang

Tan²,

Guo

et al. 2019

Cancer Medicine

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“…Various reports highlight a 20 to 50% incidence of post-radiation primary hypothyroidism after neck irradiation, 11,12 likely dependent on the dose of radiation delivered to the thyroid bed. 13 The incidence and sequelae of radiation-induced hypothyroidism in the head and neck cancer survivor are significant, and routine screening of thyroid function is recommended in the National Comprehensive Cancer Network (NCCN) guidelines. 14 The effects of radiation on the pituitary gland are also well described, with evidence of dose-dependent pituitary insufficiency.…”

Section: Introductionmentioning

confidence: 99%

Pituitary Dysfunction after Radiation for Anterior Skull Base Malignancies: Incidence and Screening

et al. 2019

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Background Management of anterior cranial base malignancies requires multidisciplinary care. Radiation therapy remains a mainstay of definitive or adjuvant treatment. Apart from primary hypothyroidism, the effects of radiation on the hypothalamic–pituitary axis after high-dose treatment of head and neck malignancies remain poorly described. We describe a comprehensive screening protocol for surveillance and characterize the incidence of pituitary dysfunction after radiation for anterior cranial base malignancies. Methods A review of patients prospectively enrolled in a skull base registry at an academic center was performed. Included patients had a history of anterior skull base malignancy and external beam radiation to the primary site, with comprehensive post-treatment pituitary serologies and at least 1 year of post-radiation follow-up. Routine hormonal screening was initiated during the study period for all patients with anterior skull base irradiation. Results Eighty-one patients met inclusion. Fifty-eight patients (71%) demonstrated some laboratory abnormality. Thirty patients (37%) demonstrated evidence of hypopituitarism. Twenty-four (29%) demonstrated central hypogonadism, and 16% of patients showed central hypothyroidism. Ten patients (12%) displayed central adrenal insufficiency with six patients demonstrating panhypopituitarism. Primary tumor location and maximum dose of radiation to the gland appeared to correlate with incidence of hypopituitarism. Conclusion Radiation for malignancies of the anterior skull base resulted in a 37% incidence of hypopituitarism in our study. Given the potential morbidity of hypopituitarism, we recommend annual post-treatment screening in these patients. We describe a comprehensive set of serologies that can be utilized, and recommend updating clinical guidelines to reflect the necessity of this screening.

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“…The lowest mean dose at which thyroid dysfunction was seen, was at 4804cGy. In the study by Ling et al 31 the lowest mean dose at which thyroid abnormality occurred was noted to be at 29.8 Gy. In the study by Kim et al 7 there was a positive correlation between higher mean dose to the thyroid and thyroid dysfunction.…”

Section: Discussionmentioning

confidence: 92%

Evaluation of Thyroid Dysfunction in Patients with Head and Neck Cancer Receiving Radiation Therapy or Chemoradiation

Immanuel¹,

Sachdeva²,

Singh³

et al. 2019

jemds

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BACKGROUND Majority of head and neck tumours are locoregionally advanced at the time of diagnosis. Concurrent chemoradiotherapy is the standard of care for these patients. Radiation portals cover the primary tumour along with the whole neck, thereby including the thyroid gland in the radiation field leading to its dysfunction. The incidence of thyroid dysfunction varies from 10-46% and manifests as elevated TSH levels. We wanted to identify the incidence of thyroid dysfunction in head and neck cancer patients receiving radiation therapy or chemoradiotherapy and explore the association between radiation dose to the thyroid and thyroid dysfunction. METHODS This one-year prospective study was conducted in 82 patients with histopathologically proven head and neck cancer receiving 3D conformal radiotherapy to the neck from a 6MV linear accelerator. Patients with history of previous thyroid surgery, pre-existing thyroid disease and recurrent disease were excluded. Free T3, free T4, and TSH were obtained at baseline and then at 3 monthly intervals up to 12 months after completion of treatment. RESULTS In our study, the incidence of thyroid dysfunction was found to be 19.51%. All the cases of thyroid dysfunction had subclinical hypothyroidism. Higher mean dose to the thyroid and smaller volume of thyroid gland were found to be associated with hypothyroidism. There was no association between thyroid dysfunction and dosevolume parameters V10-V50 and primary site of involvement. Older patients were more likely to develop hypothyroidism. No association was seen between gender and mode of treatment and thyroid dysfunction. CONCLUSIONS Thyroid dysfunction after head and neck cancer continues to be underestimated and under reported, as symptoms of thyroid dysfunction may go unnoticed under the cover of other associated comorbidities and side effects of the treatment modalities. Regular testing of thyroid function in patients undergoing radiation or chemo radiation can help in diagnosing thyroid dysfunction at the subclinical stage. Larger multi-institutional studies with longer follow-up are needed to further study the morbidity associated with post radiation thyroid dysfunction.

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Correlative study of dose to thyroid and incidence of subsequent dysfunction after head and neck radiation

Abstract: Achieving D <50 Gy, V <50%, and mean dose <54.58 Gy during RT planning may decrease the incidence; whereas female sex and concurrent chemotherapy seem to increase the risk of RT-induced hypothyroidism. © 2016 Wiley Periodicals, Inc. Head Neck 39: 548-554, 2017.

Cited by 30 publications

References 34 publications

Thyroid dose‐volume thresholds for the risk of radiation‐related hypothyroidism in nasopharyngeal carcinoma treated with intensity‐modulated radiotherapy—A single‐institution study

Thyroid dose‐volume thresholds for the risk of radiation‐related hypothyroidism in nasopharyngeal carcinoma treated with intensity‐modulated radiotherapy—A single‐institution study

Pituitary Dysfunction after Radiation for Anterior Skull Base Malignancies: Incidence and Screening

Evaluation of Thyroid Dysfunction in Patients with Head and Neck Cancer Receiving Radiation Therapy or Chemoradiation

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