Thyroid-stimulating hormone suppression for protection against hypothyroidism due to craniospinal irradiation for childhood medulloblastoma/primitive neuroectodermal tumor

Thyroid abnormalities in patients with Hodgkin lymphoma: The importance of close surveillance

INTRODUCTION

Survival in paediatric patients with Hodgkin lymphoma (HL) has increased over the last decades. However, these patients are at increased risk of developing late thyroid sequelae due to the treatment with irradiation and alkylating agents.

METHODS

We conducted an observational and retrospective study in patients with a diagnosis of HL between 2007 and 2022, in a hospital that is a paediatric oncology reference centre, through the review of electronic health records. We collected data on demographic (age, sex), clinical, radiological and histopathological variables, the dosage of alkylating agents and radiotherapy (RT) and on thyroid disorders using Microsoft Excel. The data analysis was conducted with SPSS version 17, using the Fisher exact test for qualitative data, a nonparametric test for quantitative data and Kaplan-Meier curves.

RESULTS

Sixty patients received a diagnosis of HL from 2007 to 2022. The median duration of follow-up was 78.5 months. There were 4 detected cases of hypothyroidism, 5 of thyroid nodules and 1 of subclinical hyperthyroidism. Treatment with RT was significantly associated with the development of hypothyroidism (P= .026), thyroid nodules (P= .01) and thyroid disease overall (P= .003). We estimated that the risk of thyroid disease increased 8-fold with each additional Grey received (hazard ratio, 1.081; 95% CI, 1.014-1.152; P= .017).

CONCLUSION

Hodgkin lymphoma patients treated with RT are at increased risk of late thyroid disorders, mainly hypothyroidism and malignancy. This risk is greater the higher the RT dosage and the longer the follow-up. We did not find evidence of an association between the use of alkylating agents and an increase in the risk of thyroid disease.

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.

Long-term results of suppressing thyroid-stimulating hormone during radiotherapy to prevent primary hypothyroidism in medulloblastoma/PNET and Hodgkin lymphoma: a prospective cohort study

Primary hypothyroidism commonly occurs after radiotherapy (RT), and coincides with increased circulating thyroid-stimulating hormone (TSH) levels.We tested therefore the protective effect of suppressing TSH with L-thyroxine during RT for medulloblastoma/PNET and Hodgkin lymphoma (HL) in a prospective cohort study. From1998 to 2001, a total of 37 euthyroid children with medulloblastoma/PNET plus 14 with HL, scheduled for craniospinal irradiation and mediastinum/neck radiotherapy, respectively, underwent thyroid ultrasound and free triiodothyronine (FT3), free thyroxine (FT4), and TSH evaluation at the beginning and end of craniospinal iiradiation. From 14 days before and up to the end of radiotherapy, patients were administered L-thyroxine checking every 3 days TSH to ensure a value < 0.3 μIU/mL. During follow-up, blood tests and ultrasound were repeated; primary hypothyroidism was considered an increased TSH level greater than normal range. Twenty-two/37 patients with medulloblastoma/PNET and all the 14 patients with HL were alive after a median 231 months from radiotherapy with 7/22 and 8/14 having correctly reached TSH levels < 0.3 μIU/mL and well matched for other variables. Twenty years on, hypothyroidism-free survival rates differed significantly, being 60% ± 15% and 15.6% ± 8.2% in TSH-suppressed vs. not-TSH suppressed patients, respectively (P = 0.001). These findings suggest that hypothyroidism could be durably prevented in two populations at risk of late RT sequelae, but it should be confirmed in a larger cohort.

Thyroid Sequelae of Pediatric Cancer Therapy

The hypothalamic-pituitary-thyroid axis is a common site of unintended, acquired disease either during or after the treatment of cancer. Children treated with external radiation therapy are at the highest risk for developing a thyroid-related late effect, but thyroid dysfunction and second primary thyroid neoplasms can also occur after treatment with radiopharmaceutical agents such as 131I-metaiodobenzylguanidine. Increasingly recognized is the development of early thyroid dysfunction as an off-target consequence of the more novel cancer therapeutics such as the tyrosine kinase inhibitors and immune checkpoint inhibitors. Thyroid sequelae resulting from irradiation may manifest only after years to decades of follow-up, and their resultant clinical symptoms may be indolent and non-specific. Therefore, lifelong monitoring of the childhood cancer survivor at risk for thyroid disease is paramount. In this comprehensive review, the myriad thyroid adverse effects resulting from pediatric cancer treatment are discussed and an overview of screening and treatment of these thyroid sequelae provided.

Thyroid dysfunction in patients with childhood-onset medulloblastoma or primitive neuroectodermal tumor

PURPOSE

We investigated the clinical characteristics of patients who developed thyroid dysfunction and evaluated the risk factors for hypothyroidism following radiotherapy and chemotherapy in pediatric patients with medulloblastoma or primitive neuroectodermal tumor (PNET).

METHODS

The medical records of 66 patients (42 males) treated for medulloblastoma (n=56) or PNET (n=10) in childhood between January 2000 and December 2014 at Seoul National University Children's Hospital were retrospectively reviewed. A total of 21 patients (18 high-risk medulloblastoma and 3 PNET) underwent high-dose chemotherapy and autologous stem cell rescue (HDCT/ASCR).

RESULTS

During the median 7.6 years of follow-up, 49 patients (74%) developed transient (n=12) or permanent (n=37) hypothyroidism at a median 3.8 years of follow-up (2.9-4.6 years). Younger age (&lt;5 years) at radiation exposure (P=0.014 vs. ≥9 years) and HDCT (P=0.042) were significantly predictive for hypothyroidism based on log-rank test. However, sex, type of tumor, and dose of craniospinal irradiation (less vs. more than 23.4 Gy) were not significant predictors. Cox proportional hazard model showed that both younger age (&lt;5 years) at radiation exposure (hazard ratio [HR], 3.1; vs. ≥9 years; P=0.004) and HDCT (HR, 2.4; P=0.010) were significant predictors of hypothyroidism.

CONCLUSION

Three-quarters of patients with pediatric medulloblastoma or PNET showed thyroid dysfunction, and over half had permanent thyroid dysfunction. Thus, frequent monitoring of thyroid function is mandatory in all patients treated for medulloblastoma or PNET, especially, in very young patients and/or high-risk patients recommended for HDCT/ASCR.

Predictors of Hypothyroidism in Hodgkin Lymphoma Survivors After Intensity Modulated Versus 3-Dimensional Radiation Therapy

PURPOSE

To identify predictors of hypothyroidism after chemoradiation therapy for Hodgkin lymphoma (HL) and to compare outcomes after intensity modulated radiation therapy (IMRT) with those after 3-dimensional (3D) conformal radiation therapy (CRT).

METHODS AND MATERIALS

Ninety patients who underwent involved-site IMRT in 2009 through 2014 were evaluated for treatment-induced hypothyroidism, defined as elevated thyroid-stimulating hormone or decreased free thyroxine levels (or both). Receiver operating characteristic curve analysis identified individuals at low versus high risk based on dosimetric variables. Dosimetric cutoff points were verified with an external data set of 50 patients who underwent 3D-CRT.

RESULTS

In the IMRT group, most patients (75 [83%]) had stage II HL, and the median prescribed dose was 30.6 Gy; in the 3D-CRT group, 32 patients (64%) had stage II HL, and the median prescribed dose was 32.0 Gy. No differences were found in the proportions of patients with bilateral (P = .982) or unilateral (P = .074) neck involvement between the 2 groups. Hypothyroidism rates were marginally higher in the IMRT group, with estimated 3-year rates of freedom from hypothyroidism of 56.1% in the 3D-CRT group and 40% in the IMRT group (P = .057). Univariate analysis showed that smaller thyroid volume and higher thyroid dose were associated with hypothyroidism in both groups (P < .05). In the IMRT group, the percentage of the thyroid gland volume receiving ≥25 Gy (V25) and the absolute volume of the thyroid gland spared from 25 Gy (VS25Gy) were the strongest predictors of hypothyroidism (P = .001 and P < .001, respectively). Cutoff points of 63.5% (V25) and 2.2 mL (VS25Gy) classified patients as high risk (80%-82%) or low risk (37%-44%) (P < .001). Use of a thyroid avoidance structure reduced the incidence of hypothyroidism (P < .05) in the IMRT group.

CONCLUSIONS

The percentage of the thyroid receiving 25 Gy and the volume of the thyroid spared from 25 Gy predicted the risk of hypothyroidism after either IMRT or 3D-CRT for HL. IMRT may confer a higher risk than 3D-CRT unless a treatment avoidance structure is used during planning.

Endocrine outcomes with proton and photon radiotherapy for standard risk medulloblastoma

BACKGROUND

Endocrine dysfunction is a common sequela of craniospinal irradiation (CSI). Dosimetric data suggest that proton radiotherapy (PRT) may reduce radiation-associated endocrine dysfunction but clinical data are limited.

METHODS

Seventy-seven children were treated with chemotherapy and proton (n = 40) or photon (n = 37) radiation between 2000 and 2009 with ≥3 years of endocrine screening. The incidence of multiple endocrinopathies among the proton and photon cohorts is compared. Multivariable analysis and propensity score adjusted analysis are performed to estimate the effect of radiotherapy type while adjusting for other variables.

RESULTS

The median age at diagnosis was 6.2 and 8.3 years for the proton and photon cohorts, respectively (P = .010). Cohorts were similar with respect to gender, histology, CSI dose, and total radiotherapy dose and whether the radiotherapy boost was delivered to the posterior fossa or tumor bed. The median follow-up time was 5.8 years for proton patients and 7.0 years for photon patients (P = .010). PRT was associated with a reduced risk of hypothyroidism (23% vs 69%, P < .001), sex hormone deficiency (3% vs 19%, P = .025), requirement for any endocrine replacement therapy (55% vs 78%, P = .030), and a greater height standard deviation score (mean (± SD) -1.19 (± 1.22) vs -2 (± 1.35), P = .020) on both univariate and multivariate and propensity score adjusted analysis. There was no significant difference in the incidence of growth hormone deficiency (53% vs 57%), adrenal insufficiency (5% vs 8%), or precocious puberty (18% vs 16%).

CONCLUSIONS

Proton radiotherapy may reduce the risk of some, but not all, radiation-associated late endocrine abnormalities.

Alpha lipoic acid attenuates radiation-induced thyroid injury in rats

Exposure of the thyroid to radiation during radiotherapy of the head and neck is often unavoidable. The present study aimed to investigate the protective effect of α-lipoic acid (ALA) on radiation-induced thyroid injury in rats. Rats were randomly assigned to four groups: healthy controls (CTL), irradiated (RT), received ALA before irradiation (ALA + RT), and received ALA only (ALA, 100 mg/kg, i.p.). ALA was treated at 24 h and 30 minutes prior to irradiation. The neck area including the thyroid gland was evenly irradiated with 2 Gy per minute (total dose of 18 Gy) using a photon 6-MV linear accelerator. Greater numbers of abnormal and unusually small follicles in the irradiated thyroid tissues were observed compared to the controls and the ALA group on days 4 and 7 after irradiation. However, all pathologies were decreased by ALA pretreatment. The quantity of small follicles in the irradiated rats was greater on day 7 than day 4 after irradiation. However, in the ALA-treated irradiated rats, the numbers of small and medium follicles were significantly decreased to a similar degree as in the control and ALA-only groups. The PAS-positive density of the colloid in RT group was decreased significantly compared with all other groups and reversed by ALA pretreatment. The high activity index in the irradiated rats was lowered by ALA treatment. TGF-ß1 immunoreactivity was enhanced in irradiated rats and was more severe on the day 7 after radiation exposure than on day 4. Expression of TGF-ß1 was reduced in the thyroid that had undergone ALA pretreatment. Levels of serum pro-inflammatory cytokines (TNF-α, IL-1ß and IL-6) did not differ significantly between the all groups. This study provides that pretreatment with ALA decreased the severity of radiation-induced thyroid injury by reducing inflammation and fibrotic infiltration and lowering the activity index. Thus, ALA could be used to ameliorate radiation-induced thyroid injury.

[Thyroid disorders associated with external radiation in children and adolescents]

The effects of ionizing radiation on the thyroid have been studied for several decades, and nuclear accidents are the major source of information about the subject. There is an association of hypothyroidism, hyperthyroidism, thyroid nodules and cancer with radiation, but the threshold dose, mechanism of injury, and some risk factors have not been fully established. Children are more susceptible to thyroid injury caused by radiation and require prolonged follow-up after exposure. This issue is especially relevant nowadays, since a large number of people treated with radiation for childhood cancer survive and may have sequelae. Diagnostic radiology tests also represent a source of exposure to radiation in the pediatric population. In this review, we analyze different clinical and pathological changes, and the mechanisms of thyroid lesions caused by radiotherapy and computed tomography in children and adolescents. It is important to understand these data for prevention, early detection, and treatment of thyroid dysfunction.

The evaluation of function and the ultrasonographic picture of thyroid in children treated for medulloblastoma

PURPOSE

Medulloblastoma (MB) is one of the most frequent and sensitive to radiation aggressive brain tumor in children. Abnormalities of the thyroid function are common complications of head and neck irradiation for childhood cancer. The aim of this study was to assess thyroid function in children treated for medulloblastoma according to the treatment protocol phase.

PATIENTS AND METHODS

Twenty-three children with MB were enrolled to this study. All patients underwent chemotherapy and radiotherapy to the whole craniospinal axis and boost with the conformal therapy restricted to the tumor bed to a total dose of 54 Gy. Thyroid function was evaluated based on thyroid-stimulating hormone (TSH), free thyroxine (fT4) levels controlled before MB treatment, directly after irradiation and at the end of the treatment protocol. Ultrasonography has been used to detect parenchymal abnormalities.

RESULTS

All patients presented normal thyroid hormone range before chemotherapy. Hypothyroidism was found in 12 patients in the course of treatment, in 2 patients hormone deficits diagnosed directly after irradiation, in 10 patients such condition was observed at the end of the whole therapy. All of these patients needed thyroid hormone substitution. None of them presented clinical symptoms of hypothyroidism. Ultrasound-detected abnormalities have been found in 20 patients.

CONCLUSIONS

It is crucial to monitor the functions of the thyroid gland in children treated for medulloblastoma because of the high risk of hypothyroidism resulting from the treatment. The change in the echogenicity of the thyroid gland may be an early marker for a dysfunction of this organ in children treated for medulloblastoma.

TSH suppression as a possible means of protection against hypothyroidism after irradiation for childhood Hodgkins lymphoma

Hypothyroidism remains a common late effect after irradiation of the neck/mediastinum for Hodgkins lymphoma (HL). We evaluated the protective effect of TSH suppression during neck/mediastinum irradiation. From 1998 to 2001, 14 consecutive euthyroid children were given, before and until the end of their radiotherapy on neck/mediastinum, L-thyroxine at TSH-suppressive doses. The 14 patients had adequate TSH suppression during irradiation in 8, inadequate in 6. The 8-year hypothyroidism-free-survival after irradiation was 75 ± 15% for the former group, 0% for the latter (P = 0.009). TSH suppression could have a protective effect on thyroid function as shown in a small group of patients with HL.

Hypothyroidism after head-and-neck radiotherapy in children and adolescents: preliminary results of the "Registry for the Evaluation of Side Effects After Radiotherapy in Childhood and Adolescence" (RiSK)

PURPOSE

The "Registry for the Evaluation of Side Effects After Radiotherapy in Childhood and Adolescence" (RiSK) has been established to prospectively characterize dose-volume effects of radiation in terms of side effects. The aim of this analysis was to characterize the function of the thyroid gland after radiotherapy to the head-and-neck region in children and adolescents.

METHODS AND MATERIALS

Detailed information regarding radiation doses to at-risk organs has been collected across Germany since 2001. Thyroid function was evaluated by blood value examinations of thyroid-stimulating hormone, triiodothyronine, and thyroxine. Information regarding thyroid hormone substitution was requested from the treating physicians.

RESULTS

Until May 2009, 1,086 patients from 62 centers were recruited, including 404 patients (median age, 10.9 years) who had received radiotherapy to the thyroid gland and/or hypophysis. Follow-up information was available for 264 patients (60.9%; median follow-up, 40 months), with 60 patients (22.7%) showing pathologic values. In comparison to patients treated with prophylactic cranial irradiation (median dose, 12 Gy), patients with radiation doses of 15 to 25 Gy to the thyroid gland had a hazard ratio of 3.072 (p=0.002) for the development of pathologic thyroid blood values. Patients with greater than 25 Gy to the thyroid gland and patients who underwent craniospinal irradiation had hazard ratios of 3.768 (p=0.009) and 5.674 (p<0.001), respectively. The cumulative incidence of thyroid hormone substitution therapy did not differ between defined subgroups.

CONCLUSIONS

Radiation-induced thyroid function impairment, including damage to the thyroid gland and/or hypophysis, can frequently be observed after radiotherapy in children. A structured follow-up examination is advised.