Evaluation of clinical hypothyroidism risk due to irradiation of thyroid and pituitary glands in radiotherapy of nasopharyngeal cancer patients

Research landscape of radiotherapy for nasopharyngeal carcinoma from 1959 to 2022: A bibliometric analysis

Background

Radiotherapy, as the main treatment method for nasopharyngeal carcinoma (NPC), has evolved over time, but there has been no bibliometric study on NPC radiotherapy to date. In our study, the scientific achievements of NPC radiotherapy around the world were evaluated by bibliometric analyses, and the previous research hotspots and future trends are described.

Methods

Original articles related to NPC radiotherapy were obtained from the Web of Science Core Collection. To identify research hotspots and future trends, countries/regions, institutions, journals, references, authors, and keywords were evaluated and visualized by Excel, VOSviewer, and CiteSpace.

Results

From 1959 to 2022, 7139 original articles were collected. The annual publications showed an increasing trend, especially after 2011. China had the most publications (n = 3719, 52.09 %). Sun Yat-sen University has the most publications and citations among institutions. Jun Ma is most productive and SR Baker has the highest co-cited centrality. International Journal of Radiation Oncology-Biology-Physics is the core journal, with most publications, citations and co-citations. Analysis of keywords showed intensity-modulated radiotherapy and chemoradiotherapy were the main keywords, and multicenter showed the strongest burst.

Conclusion

NPC radiotherapy has attracted increasing attention, and precision and artificial intelligence may be the future trends in this field.

Using machine learning algorithm to analyse the hypothyroidism complications caused by radiotherapy in patients with head and neck cancer

Machine learning algorithms were used to analyze the odds and predictors of complications of thyroid damage after radiation therapy in patients with head and neck cancer. This study used decision tree (DT), random forest (RF), and support vector machine (SVM) algorithms to evaluate predictors for the data of 137 head and neck cancer patients. Candidate factors included gender, age, thyroid volume, minimum dose, average dose, maximum dose, number of treatments, and relative volume of the organ receiving X dose (X: 10, 20, 30, 40, 50, 60 Gy). The algorithm was optimized according to these factors and tenfold cross-validation to analyze the state of thyroid damage and select the predictors of thyroid dysfunction. The importance of the predictors identified by the three machine learning algorithms was ranked: the top five predictors were age, thyroid volume, average dose, V50 and V60. Of these, age and volume were negatively correlated with thyroid damage, indicating that the greater the age and thyroid volume, the lower the risk of thyroid damage; the average dose, V50 and V60 were positively correlated with thyroid damage, indicating that the larger the average dose, V50 and V60, the higher the risk of thyroid damage. The RF algorithm was most accurate in predicting the probability of thyroid damage among the three algorithms optimized using the above factors. The Area under the receiver operating characteristic curve (AUC) was 0.827 and the accuracy (ACC) was 0.824. This study found that five predictors (age, thyroid volume, mean dose, V50 and V60) are important factors affecting the chance that patients with head and neck cancer who received radiation therapy will develop hypothyroidism. Using these factors as the prediction basis of the algorithm and using RF to predict the occurrence of hypothyroidism had the highest ACC, which was 82.4%. This algorithm is quite helpful in predicting the probability of radiotherapy complications. It also provides references for assisting medical decision-making in the future.

Prevalence of pituitary hormone dysfunction following radiotherapy for sinonasal and nasopharyngeal malignancies

BACKGROUND

There are limited studies and no surveillance protocols on pituitary dysfunction for adults who underwent anterior skull base radiation.

METHODS

Cross-sectional study of 50 consecutive patients with sinonasal or nasopharyngeal cancer who underwent definitive radiotherapy. The mean radiation doses, prevalence of pituitary dysfunction, and associated factors were calculated.

RESULTS

Pituitary hormone levels were abnormal in 23 (46%) patients, including 6 (12%) with symptomatic abnormalities requiring treatment. The most common hormonal abnormality was hyperprolactinemia (30%), central hypothyroidism (8%) and central hypogonadism (6%). Patients with abnormal pituitary hormone values received higher mean radiation doses to the pituitary gland (1143 cGy, P = 0.04), pituitary stalk (1129 cGy, P = 0.02), optic chiasm (1094 cGy, P = 0.01), and hypothalamus (900 cGy, P = 0.01).

CONCLUSIONS

Nearly half of the patients had abnormal pituitary function, including over a tenth requiring treatment. There may be a dose-dependent association between hormonal dysfunction and radiation.

Risk factors of early thyroid dysfunction after definitive radiotherapy in nasopharyngeal carcinoma patients

BACKGROUND

To explore the patterns and risk factors of early thyroid dysfunction in nasopharyngeal carcinoma (NPC) patients within 1 year after intensity-modulated radiation therapy (IMRT).

METHODS

Patients with NPC who received definitive IMRT between April 2016 and April 2020 were included. All patients had normal thyroid function before definitive IMRT. The chi-square test, Student's T-test, Mann-Whitney U test, Kaplan-Meier method, receiver operating characteristics curve, and Cox proportional hazard analysis were used for statistical analysis.

RESULTS

A total of 132 NPC patients were identified. Of these patients, 56 (42.4%) had hypothyroidism and 17 (12.9%) had hyperthyroidism. The median time to hypothyroidism and hyperthyroidism was 9 months (range, 1-12 months) and 1 month (range, 1-6 months) after definitive IMRT, respectively. In patients with hypothyroidism, 41 (73.2%) had subclinical hypothyroidism and 15 (26.8%) had clinical hypothyroidism. In those with hyperthyroidism, 12 patients (70.6%) had subclinical hyperthyroidism, and five patients (29.4%) had clinical hyperthyroidism. Age, clinical stage, thyroid volume, and V45 were independent risk factors for early radiation-induced hypothyroidism within 1 year after IMRT. Patients aged <47 years, stage III/IV disease, or pre-irradiation thyroid volume < 14 cm3 had higher risks of developing hypothyroidism.

CONCLUSION

Primary subclinical hypothyroidism was the most common subtype of early thyroid dysfunction in NPC patients within 1 year after IMRT. Age, clinical stage, thyroid volume, and V45 were independent risk factors for early radiation-induced hypothyroidism in NPC patients.

Multivariate NTCP Model of Hypothyroidism After Intensity-Modulated Radiotherapy for Nasopharyngeal Carcinoma

Objective

To evaluate the incidence of hypothyroidism in patients with nasopharyngeal carcinoma after intensity-modulated radiotherapy (IMRT), analyze its correlation with multiple influencing factors such as thyroid exposure dose, thyroid volume, and gender, and construct a multivariate-based normal tissue complication probability (NTCP) model for the occurrence of hypothyroidism after IMRT.

Materials and Methods

The thyroid hormone levels of patients at different points in time before and after radiotherapy were tested, and statistics on the incidence of hypothyroidism after treatment were obtained. The dose-volume data of patients’ thyroids were converted into EQD2 equivalent dose values. The correlation between hypothyroidism after radiotherapy and thyroid exposure dose, thyroid volume, gender, and other factors was analyzed, and an NTCP model was constructed.

Results

A total of 69 patients with nasopharyngeal carcinoma were enrolled in this study. Twelve months after radiotherapy, a total of 24 patients (34.8%) developed hypothyroidism. Univariate analysis and multivariate analysis revealed that the average thyroid dose and thyroid volume are the most important factors affecting hypothyroidism after radiotherapy. The NTCP model constructed based on the average dose and thyroid volume has a good degree of fit.

Conclusion

The volume and average dose of the thyroid gland are the key factors affecting the occurrence of hypothyroidism in patients with nasopharyngeal carcinoma after radiotherapy. The NTCP model constructed based on multivariate construction suggests that reducing the average dose of the thyroid to the greatest extent is an effective way to protect thyroid functions.

Outcomes of patients with nasopharyngeal carcinoma treated with intensity-modulated radiotherapy

Nasopharyngeal cancer shows a good response to intensity-modulated radiotherapy. However, there is no clear evidence for the benefits of routine use of image-guided radiotherapy. The purpose of this study was to perform a retrospective investigation of the treatment outcomes, treatment-related complications and prognostic factors for nasopharyngeal cancer treated with intensity-modulated radiotherapy and image-guided radiotherapy techniques. Retrospective analysis was performed on 326 consecutive nasopharyngeal cancer patients treated between 2004 and 2015. Potentially significant patient-related and treatment-related variables were analyzed. Radiation-related complications were recorded. The 5-year overall survival and disease-free survival rates of these patients were 77.9% and 70.5%, respectively. Age, AJCC (American Joint Committee on Cancer) stage, retropharyngeal lymphadenopathy, treatment interruption and body mass index were independent prognostic factors for overall survival. Age, AJCC stage, retropharyngeal lymphadenopathy, image-guided radiotherapy and body mass index were independent prognostic factors for disease-free survival. In conclusion, intensity-modulated radiotherapy significantly improves the treatment outcomes of nasopharyngeal cancer. With the aid of image-guided radiotherapy, the advantage of intensity-modulated radiotherapy might be further amplified.

Research progress of radiation-induced hypothyroidism in head and neck cancer

This paper reviews the factors related to hypothyroidism after radiotherapy in patients with head and neck cancer to facilitate the prevention of radiation-induced hypothyroidism and reduce its incidence. Hypothyroidism is a common complication after radiotherapy in patients with head and neck cancer, wherein the higher the radiation dose to the thyroid and pituitary gland, the higher the incidence of hypothyroidism. With prolonged follow-up time, the incidence of hypothyroidism gradually increases. Intensity modulated radiotherapy should limit the dose to the thyroid, which would reduce the incidence of hypothyroidism. In addition, the risk factors for hypothyroidism include small thyroid volume size, female sex, and previous neck surgery. The incidence of radiation-induced hypothyroidism in head and neck cancer is related to the radiation dose, radiotherapy technique, thyroid volume, sex, and age. A prospective, large sample and long-term follow-up study should be carried out to establish a model of normal tissue complications that are likely to be related to radiation-induced hypothyroidism.

Thyroid V50 is a risk factor for hypothyroidism in patients with nasopharyngeal carcinoma treated with intensity-modulated radiation therapy: a retrospective study

BACKGROUND

We investigated the risk factors of radiation-induced thyroid dysfunction, then combined the clinical factors and optimum thyroid dosimetric parameters to predict the incidence rate of hypothyroidism (HT) and to guide individualized treatment.

METHODS

A total of 206 patients with histologically proven nasopharyngeal carcinoma (NPC) treated at the Cancer Hospital of the University of Chinese Academy of Sciences between January 2015 and August 2018 were included. Dose-volume histogram (DVH) data, including mean dose, absolute volume, V₂₀, V₂₅, V₃₀, V₃₅, V₄₀, V₄₅, V_50, V₅₅, and V₆₀ were extracted and used as dosimetric parameters. A logistic regression analysis model was built to identify predictors related to HT occurring within 2 years.

RESULTS

Sex, N stage, thyroid volume, mean thyroid dose, and thyroid V₂₀ and V₅₀ were significantly different between patients with and without HT. Logistic regression analysis showed that N stage, thyroid volume, and thyroid V₅₀ were independent predictors of HT. The radiosensitivity of the thyroid decreased as the thyroid volume increased. Patients with N stage > 1 had significantly higher HT incidence (37.38%) than patients with N stage ≤1 (13.11%). The incidence of HT was 54.55% in patients with thyroid V₅₀ > 24% and was 34.15% in patients with thyroid V₅₀ ≤ 24%.

CONCLUSIONS

The incidence of HT is significantly associated with N stage, thyroid volume, and thyroid V₅₀. More attention should be paid to patients with NPC with thyroid volume ≤ 12.82 cm³ and advanced N stage disease.

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

BACKGROUND

To 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.

METHODS

In 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.

RESULTS

In 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).

CONCLUSION

We 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.

A review on the dosimetrical and radiobiological prediction of radiation-induced hypothyroidism in radiation therapy of head-and-neck cancer, breast cancer, and Hodgkin’s lymphoma survivors

A review on the radiobiological modeling of radiation-induced hypothyroidism after radiation therapy of head-and-neck cancers, breast cancer, and Hodgkin’s lymphoma is presented. The current review is based on data relating to dose-volume constrains and normal tissue complication probability (NTCP) as a function of either radiobiological or (pre)treatment-clinical parameters. Also, these data were explored in order to provide more helpful criteria for radiobiological optimization of treatment plans involving thyroid gland as a critical normal organ.

Feasibility of ipsilateral lower neck sparing irradiation for unilateral or bilateral neck node-negative nasopharyngeal carcinoma: systemic review and meta-analysis of 2, 521 patients

Background

To compare the efficacy of ipsilateral lower neck sparing irradiation (ILNSI) versus ipsilateral lower neck prophylactic irradiation (ILNPI) for unilateral or bilateral neck node-negative nasopharyngeal cancer (NPC).

Methods

A comprehensive literature search of PubMed, EMBASE, the Cochrane Library and other public databases was conducted in October, 2017. The outcomes were 3-year overall/regional recurrence-free/disease-free/distant metastasis-free survival (OS/RRFS/DFS/DMFS) and ipsilateral lower neck (ILN) recurrence. We performed subgroup analysis of ILNSI versus ILNPI for different radiotherapy techniques. Sensitivity analysis was performed to examine the stability of the results.

Results

Nine head-to-head comparative studies (2, 521 patients) were included in the meta-analysis. For the comparison of ILNSI versus ILNPI, there was no significant difference in 3-year OS (HR = 1.16, 95% confidence interval [CI] = 0.85–1.58, P = 0.36), RRFS (HR = 1.37, 95% CI = 0.76–2.47, P = 0.30), DFS (HR = 1.08, 95% CI = 0.80–1.44, P = 0.62) and DMFS (HR = 1.00, 95% CI = 0.69–1.44, P = 0.99). ILNSI and ILNPI also led to equivalent ILN recurrence rates (OR = 0.98, 95% CI = 0.47–2.03, P = 0.96). No significant heterogeneity was observed for any outcome. Subgroup analysis confirmed no significant differences between ILNSI and ILNPI for any outcome, regardless of radiotherapy technique. Sensitivity analysis indicated all outcomes were highly stable in favor of the original conclusions.

Conclusions

ILNSI provided equivalent survival outcomes and regional control compared to ILNPI; ILNSI represents an appropriate alternative strategy for patients with unilateral or bilateral neck node-negative NPC.

Electronic supplementary material

The online version of this article (10.1186/s13014-018-1087-x) contains supplementary material, which is available to authorized users.

Pattern of radiation-induced thyroid gland changes in nasopharyngeal carcinoma patients in 48 months after radiotherapy

OBJECTIVES

Radiation-induced hypothyroidism is the most common thyroid disorder after radiotherapy in nasopharyngeal carcinoma (NPC) patients. This study evaluated the pattern of radiation-induced thyroid gland changes in 48 months after radiotherapy in NPC patients and the association of hypothyroidism incidence with thyroid dose.

METHODS

Fifty-six NPC patients treated by intensity modulated radiotherapy in 2013 were recruited. All patients received baseline thyroid hormones (fT3, fT4 and TSH) tests and CT scan before radiotherapy. Repeated measures of the thyroid hormones and gland volume were performed at 3, 6, 12, 18, 24, 30, 36 and 48 months after treatment. Trend lines of the thyroid volume and hormone level changes against time were plotted. The incidence of hypothyroidism patients and its relationship with the dose were also evaluated.

RESULTS

The mean thyroid volume followed a decreasing trend after radiotherapy, reaching a minimum (-39.8%) at 30 months and slightly increased afterward. The fT4 level followed a similar pattern with its mean value dropped by 21.5% at 30 months and became steady after 36 months. TSH level showed gradual rise from just after radiotherapy, reaching a peak at 24 months and became relatively steady after 36 months. The incidence of hypothyroidism increased to a maximum at 24 months (28.6%) and dropped afterwards. Thyroid Dmean and D50 were significantly correlated with hypothyroidism incidence in 12 to 30 months (ρ > 0.40, p < 0.05).

CONCLUSION

The patterns of radiation induced thyroid volume shrinkage and fT4 level reduction were similar, with both of them showed decreasing trend from 0 to 30 months. The thyroid volume and function reached a relatively steady state after 36 months. The incidence of hypothyroidism increased up to 24 months and its frequency was associated with the thyroid dose.

Thyroid Disorders in the Oncology Patient

Thyroid disease and cancer diagnoses are common conditions likely to coexist. Optimal management requires appropriate diagnostic testing and consideration of a number of factors, including overall health status and prognosis. Hypothyroidism and hyperthyroidism can lead to a number of symptoms that may affect not only quality of life but can interfere with the patient’s ability to tolerate cancer treatment. Imaging studies performed for cancer staging can identify incidental structural abnormalities in the thyroid, which should be assessed with dedicated neck ultrasonography and possibly fine-needle aspiration. Incidental thyroid cancer is most often less urgent than the patient’s presenting malignancy and can be addressed surgically when appropriate in the context of other treatments (i.e., chemotherapy). Providers working in an oncology setting, as well as primary care providers, should be aware of medications that are associated with hormonal abnormalities. Any patient with a history of neck or brain radiation therapy is at risk of developing hypothyroidism and possibly other endocrinopathies. Complex or very ill patients may benefit from a multidisciplinary approach that utilizes the experience of a knowledgeable endocrinologist.