The threshold of hypothyroidism after radiation therapy for head and neck cancer: a retrospective analysis of 116 cases

Normal tissue complication probability models of hypothyroidism after radiotherapy for breast cancer

Purpose

We aimed to develop Lyman-Kutcher-Burman (LKB) and multivariable normal tissue complication probability (NTCP) models to predict the risk of radiation-induced hypothyroidism (RIHT) in breast cancer patients.

Materials and methods

A total of 1,063 breast cancer patients who underwent whole breast irradiation between 2009 and 2016 were analyzed. Individual dose-volume histograms were used to generate LKB and multivariable logistic regression models. LKB model was fit using the thyroid radiation dose-volume parameters. A multivariable model was constructed to identify potential dosimetric and clinical parameters associated with RIHT. Internal validation was conducted using bootstrapping techniques, and model performance was evaluated using the area under the curve (AUC) and Hosmer-Lemeshow (HL) goodness-of-fit test.

Results

RIHT developed in 4 % of patients with a median follow-up of 77.7 months. LKB and multivariable NTCP models exhibited significant agreement between the predicted and observed results (HL P values > 0.05). The multivariable NTCP model outperformed the LKB model in predicting RIHT (AUC 0.62 vs. 0.54). In the multivariable model, systemic therapy, age, and percentage of thyroid volume receiving ≥ 10 Gy (V10) were significant prognostic factors for RIHT. The cumulative incidence of RIHT was significantly higher in patients who exceeded the cut-off values for all three risk predictors (systemic therapy, age ≥ 40 years, and thyroid V10 ≥ 26 %, P < 0.005).

Conclusions

Systemic therapy, age, and V10 of the thyroid were identified as strong risk factors for the development of RIHT. Our NTCP models provide valuable insights to clinicians for predicting and preventing hypothyroidism by identifying high-risk patients.

Development and validation of a machine learning model of radiation-induced hypothyroidism with clinical and dose-volume features

BACKGROUND AND PURPOSE

Radiation-induced hypothyroidism (RIHT) is a common but underestimated late effect in head and neck cancers. However, no consensus exists regarding risk prediction or dose constraints in RIHT. We aimed to develop a machine learning model for the accurate risk prediction of RIHT based on clinical and dose-volume features and to evaluate its performance internally and externally.

MATERIALS AND METHODS

We retrospectively searched two institutions for patients aged >20 years treated with definitive radiotherapy for nasopharyngeal or oropharyngeal cancer, and extracted their clinical information and dose-volume features. One was designated the developmental cohort, the other as the external validation cohort. We compared the performances of machine learning models with those of published normal tissue complication probability (NTCP) models.

RESULTS

The developmental and external validation cohorts consisted of 378 and 49 patients, respectively. The estimated cumulative incidence rates of grade ≥1 hypothyroidism were 53.5% and 61.3% in the developmental and external validation cohorts, respectively. Machine learning models outperformed traditional NTCP models by having lower Brier scores at every time point and a lower integrated Brier score, while demonstrating a comparable calibration index and mean area under the curve. Even simplified machine learning models using only thyroid features performed better than did traditional NTCP algorithms. The machine learning models showed consistent performance between folds. The performance in a previously unseen external validation cohort was comparable to that of the cross-validation.

CONCLUSIONS

Our model outperformed traditional NTCP models, with additional capabilities of predicting the RIHT risk at individual time points. A simplified model using only thyroid dose-volume features still outperforms traditional NTCP models and can be incorporated into future treatment planning systems for biological optimization.

An Analytical Study to Determine Dose-Volume Threshold for Radiation Induced Hypothyroidism

Objective: To determine radiation dose volume threshold in predicting the development of hypothyroidism in cancer patients following neck irradiation. Methods: This is a cross sectional follow up study for patients who had been previously irradiated, prior to enrolment in the study. We have done thyroid dose-volumetric analysis on 120 histologically proven cancer patients in the age group of 18-75 years who received neck irradiation as a part of their definitive or adjuvant radiotherapy with three-dimensional conformal or intensity-modulated radiotherapy technique (3D -CRT or IMRT) and completed at least six months post-radiotherapy. Primary tumor sites included carcinoma or lymphoma of the head and neck, breast, cervical, and upper thoracic esophagus, requiring neck irradiation. Results: The proportion of patients who tested positive for Radiation induced hypothyroidism (RIHT) was found to be 40%, with clinical hypothyroidism and subclinical hypothyroidism being 25.8% and 14.2%, respectively. Time to develop hypothyroidism peaks around two years. Mean thyroid gland dose (Dmean) >28 Gy, thyroid gland volume receiving 40 Gy dose (i.e. V40) >49% and age <50 years were found to be significant risk factors for the development of RIHT on binary logistic regression. RT dose >50 Gy and thyroid gland volume spared from 40 Gy (i.e. VS40) < 2.12cm3 were statistically significant predictors for RIHT on chi-square and (Receiver operating characteristic) ROC curve analysis respectively but not on regression analysis. Conclusion: Dose-volume threshold for the thyroid gland as Dmean <28 Gy and V40 <49% may prevent the development of RIHT.

[Prospective evaluation of radiation-induced thyroid disorders after breast and supraclavicular irradiation]

PURPOSE

The thyroid is an endocrine gland playing a major role in metabolism and development by the secretion of T4 and T3 thyroid hormones. Due to its anatomical position, it is often included in the target volume for the irradiation of certain tumours and thus receives significant doses (10 to 80Gy). The treatment of breast cancer requires in most cases a breast irradiation associated or not with a lymph node irradiation. The aim of our study was to investigate prospectively the frequency of thyroid disorders in patients with breast cancer treated by radiation, with or without irradiation of the supra- and subclavicular lymph nodes.

MATERIAL AND METHODS

This prospective multicentre study (institut Godinot, institut de cancérologie Strasbourg Europe and institut de cancérologie de Lorraine) concerned adult patients with non-metastatic breast carcinoma treated by adjuvant irradiation. They were included in a non-randomized way between February 2013 and June 2015 and divided into two groups according to treatment: (i) breast radiotherapy associated with irradiation of the supra- and subclavicular lymph nodes (group 1), or (ii) breast irradiation alone (group 2). The dose - volume histogram of the thyroid was systematically edited by the physics department. Each patient had a consultation with an endocrinologist at the beginning of the treatment and was monitored by blood analyses including TSH, T4L, antithyroglobulin and antiperoxidase antibodies every 6 months until the 60th month after the end of radiotherapy. Data were described by numbers and percentages for qualitative variables; by means, medians, standard deviation and ranges for quantitative variables. Statistical associations were tested by Chi2, Fisher's, Student's, or analysis of variance tests depending on the conditions of application. Survival analyses were performed by log rank tests and Cox models.

RESULTS

This study initially included 500 patients, 245 in group 1 and 252 in group 2 (three patients were later excluded for false inclusion). Thyroid abnormalities occurred in 76 patients, representing an incidence of 15.3%. The mean time of the first occurrence of thyroid disorders was 24.3 months. It was more frequent in group 1 with a prevalence of 19.2% against 11.5% in group 2 (P=0.01745). A maximal radiation dose delivered to the thyroid gland greater than 20Gy (odds ratio [OR]: 1.82; P=0.018) or 30Gy (OR: 1.89; P=0.013) was significantly associated with a higher incidence of thyroid disorders, as was a mean dose greater than 30Gy (OR: 5.69; P=0.049). A percentage of thyroid volume receiving 30Gy (V30) greater than 50% (P=0.006) or greater than 62.5% (P=0.021) was significantly associated with an increased incidence of thyroid disorder and more precisely, hypothyroidism (P=0.0007). In multivariate analysis, no factor associated with the occurrence of thyroid disorder was identified. However, in the subgroup analysis concerning group 1 (receiving supraclavicular irradiation), a maximal radiation dose greater than 30Gy appeared to be a risk factor for the occurrence of thyroid disorders (P=0.040).

CONCLUSION

Thyroid disorder, and in particular hypothyroidism, may be a late side effect of locoregional breast radiotherapy. Patients receiving this treatment should have a biological monitoring of thyroid function.

Hypothyroidism following Radiotherapy for Head and Neck Cancer: A Systematic Review of the Literature and Opportunities to Improve the Therapeutic Ratio

(1) Background: Radiotherapy (RT) is a central component for the treatment of many head and neck cancers. In this systematic review of the literature, we aimed to characterize and quantify the published evidence on RT-related hypothyroidism, including estimated incidence, clinical risk factors, and dosimetric parameters that may be used to guide clinical decision making. Furthermore, we aimed to identify potential areas of improvement in the prevention and clinical management of RT-induced hypothyroidism, including the role of modern advanced therapeutic techniques. (2) Methods: We conducted a systemic review of the literature in accordance with Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. PubMed and Google Scholar were searched to identify original research articles describing the incidence, mechanism, dosimetry, treatment, or prevention of radiation-related hypothyroidism for adults receiving RT for the treatment of head and neck cancers. The snowball method was used to identify additional articles. For identified articles, we tabulated several datapoints, including publication date, patient sample size, estimated hypothyroidism incidence, cancer site/type, follow-up period, radiation modality and technique, use of multimodality therapy, method of thyroid function evaluation, and proposed dosimetric predictors of hypothyroidism. (3) Results: One hundred and eleven articles met inclusion criteria, reflecting a range of head and neck cancer subtypes. There was a large variation in the estimated incidence of RT-related hypothyroidism, with a median estimate of 36% (range 3% to 79%). Reported incidence increased in later publication dates, which was likely related to improved screening and longer follow up. There were a wide variety of predictive metrics used to identify patients at high risk of hypothyroidism, the most common of which were volumetric and mean dosimetrics related to the thyroid gland (Vxx%, Dmean). More recently, there has been increasing evidence to suggest that the thyroid gland volume itself and the volume of the thyroid gland spared from high-dose radiation (VSxx) may better predict thyroid function after RT. There were no identified studies investigating the role of advanced radiotherapeutic techniques such as MRI-guided RT or particle therapy to decrease RT-related hypothyroidism. Conclusions: Hypothyroidism is a common toxicity resulting from therapeutic radiation for head and neck cancer with recent estimates suggesting 40-50% of patients may experience hypothyroidism after treatment. Dosimetric predictive models are increasingly able to accurately identify patients at risk of hypothyroidism, especially those utilizing thyroid VS metrics. Further investigation regarding the potential for advanced radiotherapeutic therapies to decrease RT-induced thyroid dysfunction is needed.

Recurrent Esthesioneuroblastoma: Long-Term Outcomes of Salvage Therapy

INTRODUCTION

Esthesioneuroblastoma (ENB) is a rare malignant neoplasm arising from the olfactory epithelium of the cribriform plate. Although survival is excellent with a reported 5-year overall survival (OS) of 82%, recurrence is frequent and occurs in 40-50% of cases. This study investigates the characteristics of ENB recurrence and the subsequent prognosis of patients with recurrence.

METHODS

The clinical records of all patients diagnosed as having ENB with subsequent recurrence at a tertiary hospital from 1 January 1960 to 1 January 2020 were retrospectively reviewed. Overall survival (OS) and progression-free survival (PFS) were reported.

RESULTS

A total of 64 out of 143 ENB patients had recurrences. In total, 45 out of 64 recurrences met the inclusion criteria and were included in this study. From these, 10 (22%) had a sinonasal recurrence, 14 (31%) had an intracranial recurrence, 15 (33%) had a regional recurrence, and 6 (13%) had a distal recurrence. The average interval from initial treatment to recurrence was 4.74 years. There were no differences in rates of recurrence with respect to age, sex, or types of surgery (endoscopic, transcranial, lateral rhinotomy, and combined). The time to recurrence was shorter for Hyams grades 3 and 4 compared to Hyams grades 1 and 2 (3.75 years vs. 5.70 years, p < 0.05). Patients with recurrence limited to the sinonasal region had a lower overall primary Kadish stage compared to recurrences beyond the sinonasal region (2.60 vs. 3.03, p < 0.05). A total of 9 (20%) out of 45 patients developed secondary recurrence. Following recurrence, the subsequent 5-year OS and PFS were 63 and 56%, respectively. The mean time to secondary recurrence after treatment of the primary recurrence was 32 months, which was significantly shorter than the time to primary recurrence (32 months vs. 57 months, p = 0.048). The mean age of the secondary recurrence group is significantly older than the primary recurrence group (59.78 years vs. 50.31 years, p = 0.02). No statistically significant differences were observed between the secondary recurrence group and the recurrence group in terms of their overall Kadish stages or Hyams grades.

CONCLUSIONS

Following an ENB recurrence, salvage therapy appears to be an effective therapeutic option with a subsequent 5-year OS of 63%. However, subsequent recurrences are not infrequent and may require additional therapy.

Primary Hypothyroidism in Patients Exposed to Therapeutic External Beam Radiation: Non-randomized Comparative Study

Background Cancer patients are not routinely assessed for thyroid function after external beam radiotherapy (EBRT) to the neck, despite hypothyroidism being a known side effect of EBRT. So, this study aimed to assess the incidence of hypothyroidism after therapeutic external beam radiotherapy to the neck and to determine the time for the development of hypothyroidism. Methodology A non-randomized prospective comparative study was done at a tertiary care center from April 2018 to September 2020. Any cancer patients who were euthyroid before radiotherapy and are planned to receive EBRT to the neck were included as cases, whereas controls were selected from the patients who were euthyroid before radiotherapy and were planned to receive EBRT to the site other than the neck. A total of 100 participants in each case and control group were selected. Data were collected on participants' age, gender, primary tumor site, treatment modality, total radiation dose along with concurrent chemoradiation regimens. Details of blood chemistry including thyroid hormone levels were collected during the pre-radiation phase and post-radiation phase. After the completion of radiotherapy, both the patients and controls were followed up periodically at three months, six months, nine months, 12 months, and finally at 15 months post-radiation. Data were analyzed and interpreted to pursue defined objectives by using tables and graphs using Microsoft Excel and IBM SPSS, version 26.0 (Armonk, NY: IBM Corp.). The chi-square test was applied to find out the association of different variables with the development of hypothyroidism. P-values<0.05 were considered significant throughout. Results According to our findings, the incidence of hypothyroidism following external beam radiotherapy to the neck where radiation portals included a portion or the entire thyroid gland was 16% and 4%, when the radiation given to sites other than neck region. The difference in incidence between the case and control groups was found to be statically significant (p<0.05). However, it was found that age, gender, the primary tumor site, total radiation dose, and treatment modality had no significant effects on hypothyroidism development. The median time duration to become hypothyroid after EBRT was 12 months. Conclusions The monitoring of thyroid function should become a part of routine follow-up procedures in all cancer patients who receive neck radiation as part of their treatment.

Post-radiation primary hypothyroidism in patients with head and neck cancer: External validation of thyroid gland dose-volume constraints with long-term endocrine outcomes

BACKGROUND

Post-radiation primary hypothyroidism is a common late complication in head and neck cancer (HNC) survivors. No radiation dose-volume constraint of the thyroid gland has been externally validated for predicting long-term thyroid function outcomes.

MATERIALS AND METHODS

This external validation study evaluated the diagnostic properties of 22 radiation dose-volume constraints of the thyroid gland proposed in the literature. Radiation dosimetric data from 488 HNC patients who underwent neck irradiation from January 2013 to December 2015 at two tertiary oncology centers were reviewed. The diagnostic metrics of candidate constraints were computed by inverse probability of censoring weighting and compared using time-dependent receiver operating characteristic (ROC) curves with death designated as a competing event. Multivariable regression analyses were performed using the Fine-Gray sub-distribution hazard model.

RESULTS

Over a median follow-up period of 6.8 years, 205 (42.0 %) patients developed post-radiation primary hypothyroidism. The thyroid volume spared from 60 Gy (VS60) had the largest area under ROC curve of 0.698 at 5 years after radiotherapy. Of all evaluated constraints, VS60 at a cutoff value of 10 cc had the highest F-score of 0.53. The 5-year hypothyroidism risks of patients with thyroid VS60 ≥ 10 cc and < 10 cc were 14.7 % and 38.2 %, respectively (p < 0.001). The adjusted sub-hazard ratio for post-radiation primary hypothyroidism for VS60 < 10 cc was 1.87 (95 % confidence interval, 1.22-2.87; p < 0.001).

CONCLUSION

Thyroid VS60 is the best radiation dose-volume parameter to predict the long-term risk of primary hypothyroidism in patients with HNC who underwent neck irradiation. VS60 ≥ 10 cc is a robust constraint that limits the 5-year primary hypothyroidism risk to less than 15 % and should be routinely employed during radiotherapy optimization.

Early post-treatment 18F-FDG PET/CT for predicting radiation-induced hypothyroidism in head and neck cancer

BACKGROUND

Radiation-induced hypothyroidism (RIHT) is a common, but underestimated, late adverse effect in head and neck cancer. We investigated the value of early post-treatment ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computed tomography (PET/CT) for predicting RIHT.

METHODS

We searched our institutional database for patients aged ≥ 20 years who had undergone definitive radiotherapy for nasopharyngeal or oropharyngeal cancer between 2005 and 2017, followed by ¹⁸F-FDG PET/CT within 180 days of radiotherapy completion. We visually assessed and compared PET/CT and baseline characteristics in patients with and without RIHT using the chi-square test for categorical variables and the t-test for continuous variables. Variable predictive ability was evaluated by measuring the area under receiver operating characteristic curves.

RESULTS

Fifty-two patients were included; 22 (42%) developed RIHT and 30 (58%) did not. Two patients presented with diffuse thyroid uptake on PET/CT via visual assessment, and both developed RIHT later. Among the PET/CT variables, thyroid functioning volume was significantly higher in patients without RIHT than in patients with RIHT (16.30 ± 6.03 cm³ vs. 10.61 ± 3.81 cm³, p < 0.001). The maximum standard uptake values of the thyroid and pituitary glands did not differ significantly between the groups. Two patient characteristics, pretreatment thyroid volume and mean radiotherapy dose to the thyroid, also showed significant differences between the groups. An algorithmic approach combining visual grading of thyroid ¹⁸F-FDG uptake and thyroid functioning volume cutoff of 14.01 yielded an area under curve of 0.89 (95% confidence interval, 0.80-0.98); the sensitivity, specificity, positive predictive value, and negative predictive value were 87.0%, 82.3%, 80.0%, and 88.9%, respectively.

CONCLUSION

Early post-treatment PET/CT-derived thyroid functioning volume was a good predictor of RIHT development. Diffusely increased thyroid ¹⁸F-FDG uptake on PET/CT may indicate impending RIHT. Routine surveillance of thyroid function is warranted in patients at high risk of developing RIHT.

Predictive factors for thyroid complications after radiation therapy-data from a cohort of cancer patients closely followed since they were irradiated

INTRODUCTION

Cancer survivors are at an increased risk of adverse outcomes, including thyroid neoplasms, given the high radiosensitivity of this gland. The aim of this study is to assess the incidence and timeframe of thyroid complications in cancer patients, followed systematically since their radiation therapy, and to identify risk factors for the development of hypothyroidism and thyroid cancer.

METHODS

We performed a retrospective study, including 282 subjects, who received neck, craniospinal, or total body irradiation (TBI). Patients were grouped into four primary diagnostic clusters: leukaemia, Hodgkin's disease, central nervous system, and head and neck tumours.

RESULTS

Hypothyroidism was observed in 56.7% of patients, on average 6.8 ± 5.9 years after the treatment. Neck and craniospinal irradiation presented a 3.5-fold increased risk for the development of hypothyroidism compared to TBI. Papillary thyroid cancer was diagnosed in 8.5% of the patients, on average, 18.5 ± 4.9 years after radiotherapy (RT). Female gender, younger age, and lower irradiation doses were independently associated with thyroid cancer development.

CONCLUSION

Our study provides useful information about the risk of hypothyroidism and thyroid cancer after RT, as it was performed in a cohort of patients closely followed since the oncological therapies, and, thus, may give new insights into the follow-up management of these patients.

Predictors of radiation-induced hypothyroidism in nasopharyngeal carcinoma survivors after intensity-modulated radiotherapy

Background

The aim of the study is to identify clinical and dosimetric factors that could predict the risk of hypothyroidism in nasopharyngeal carcinoma (NPC) patients following intensity-modulated radiotherapy (IMRT).

Methods

A total of 404 non-metastatic NPC patients were included in our study. All patients were treated with IMRT. The thyroid function were performed for all patients before and after radiation at regular intervals. The time onset for developing hypothyroidism was defined as the time interval between the completion of RT and the first recorded abnormal thyroid hormone test. The cumulative incidence rates of hypothyroidism were estimated using Kaplan–Meier method. Univariate and multivariate Cox regression analyses were performed to detect the most promising factors that were associated with hypothyroidism.

Results

Median follow up was 60.6 months. The 3-, 5- and 7- year cumulative incidence rate of hypothyroidism was 39.4%, 49.1% and 54.7%, respectively. The median time to primary hypothyroidism and central hypothyroidism were 15.4 months (range 2.9–83.8 months) and 29.9 months (range 19.8–93.6 months), respectively. Univariate and multivariate analyses revealed that younger age, female gender and small thyroid volume were the most important factors in predicting the risk of hypothyroidism. Dtmean (mean dose of thyroid), V30-V50 (percentage of thyroid volume receiving a certain dose level) and VS45-VS60 (the absolute volumes of thyroid spared from various dose levels) remained statistically significant in multivariate analyses. Cutoff points of 45 Gy (Dtmean), 80% (Vt40) and 5 cm³ (VS45Gy) were identified to classify patients as high-risk or low-risk group.

Conclusion

Thyroid Vt40 highly predicted the risk of hypothyroidism after IMRT for NPC patients. We recommended plan optimization objectives to reduce thyroid Vt40 to 80%.

Trial registration: Retrospectively registered.

Association between Cervical Lymph Node Metastasis and the Incidence of Radiation-Induced Hypothyroidism in Nasopharyngeal Carcinoma

Background

It is controversial and unclear how N-stage would increase the risk of incidence of hypothyroidism (HT) for patients with nasopharyngeal carcinoma (NPC) after radiotherapy. Our study aimed to explore the correlation between cervical lymph node metastasis and the incidence of HT in NPC.

Materials and Methods

A total of 206 patients with NPC treated at the Cancer Hospital of University of Chinese Academy of Sciences, and their clinical information were retrospectively collected. A series of univariate logistic regression models were performed to explore the association of clinical and lymph node indices with the development of HT. Significant features in univariate analysis were then used to construct three prediction models, for HT prediction using multivariate logistic regression based on Bayesian information criterion. Prediction performance of those models was measured by area under the receiver operating characteristic curve (AUC) using 10-fold cross-validation.

Results

A total of 111 patients developed HT, and the incidence of HT in N_2–3 and N_0–1 patients was 58.82% and 44.29%, respectively. Compared to Model 1 (consisted of pretreatment TSH concentration, thyroid volume, and N-stage) whose AUCs were 0.801 and 0.766 in training and validation sets, with N-stage be replaced by shortest distance from thyroid, Model 2 achieved more stable AUCs of 0.824 and 0.801. While with numbers of positive lymph nodes in Level IIb additionally added, Model 3 improved its AUCs to 0.841 and 0.813.

Conclusion

The shortest distance between the lymph nodes and thyroid gland and the number of lymph nodes in IIb are better predictors of radiation-induced HT than the N-stage.

Dysphagia, hypothyroidism, and osteoradionecrosis after radiation therapy for head and neck cancer

OBJECTIVES

To analyze the long-term side effects of radiation therapy (RT) for head and neck cancer (HNC).

METHODS

Retrospective chart analysis of all 688 HNC patients treated during 2010-2015 at Turku University Hospital, Finland. All patients who survived for more than a year after RT/chemoRT were included (n = 233). Intensity modulated RT (IMRT) with standard fractionation was applied in each case.

RESULTS

One hundred and six patients (45%) reported persisting dysphagia, for which neck RT increased risk. Definitive neck RT to high-risk volume did not increase late toxicity risks compared to elective neck RT. Radiation-induced hypothyroidism (29%, n = 67) was more common among younger patients and females. Osteoradionecrosis (12%, n = 29) was more common in the oral cavity cancer group (20.7%, n = 92) compared to all other subsites.

CONCLUSIONS

Late toxicities of RT for HNC are common. Age, gender, tumor subsite, and neck RT affect susceptibility to long-term side effects.

LEVEL OF EVIDENCE

4.

Risk factors associated with patient-reported fatigue among long-term oropharyngeal carcinoma survivors

BACKGROUND

The study objective is to identify risk factors associated with fatigue among long-term OPC survivors.

METHODS

This cross-sectional study included disease-free OPC survivors treated curatively between 2000 and 2013 who were surveyed from September 2015 to July 2016. The outcome variable was patient-reported fatigue. Multivariable logistic regression was used to identify factors associated with moderate to severe fatigue.

RESULTS

Among 863 OPC survivors, 17.4% reported moderate to severe fatigue. Self-reported thyroid problems (OR: 2.01; p = 0.003), current cigarette smoking at time of survey (OR: 3.85; p = 0.001), late lower cranial neuropathy (OR: 3.44; p = 0.002), and female sex (OR: 1.91; p = 0.010) were concurrent risk factors of reporting moderate to severe fatigue. Ipsilateral intensity-modulated radiotherapy (OR: 0.18; p = 0.014) was associated with lower risk of reporting moderate to severe fatigue.

CONCLUSIONS

Our study identified thyroid problems, smoking, and late lower cranial neuropathy as associated with moderate to severe fatigue. These findings should be further validated in prospective studies to address fatigue among OPC survivors.

Dose-volume predictors of post-radiation primary hypothyroidism in head and neck cancer: a systematic review

•

This systematic review included 29 studies (n = 4,530 patients) on dosimetric predictors of primary hypothyroidism in HNC.

•

Average crude incidence of primary hypothyroidism after HNC radiotherapy was 41.4%.

•

Thyroid Dmean and V50 were the most widely reported dosimetric predictors for hypothyroidism.

•

Thyroid volume is a predictor of hypothyroidism (pooled aOR 0.89 per 1 cc increment) independent of radiation dosimetry.

•

Thyroid gland constraints individualized for thyroid volume are crucial in HNC radiotherapy.

Background and Purpose

This systematic review aims to identify radiation dose-volume predictors of primary hypothyroidism after radiotherapy in patients with head and neck cancer (HNC).

Materials and methods

We performed a systematic literature search of Medline, EMBASE and Web of Science from database inception to July 1, 2021 for articles that discuss radiation dose-volume predictors of post-radiation primary hypothyroidism in patients with HNC. Data on the incidence, clinical risk factors and radiation dose-volume parameters were extracted. A meta-analysis was performed using the random-effects model to estimate the pooled odds ratio (OR) of thyroid volume as a predictor of the risk of post-radiation hypothyroidism, adjusted for thyroid radiation dosimetry.

Results

Our search identified 29 observational studies involving 4,530 patients. With median follow-up durations ranging from 1.0 to 5.3 years, the average crude incidence of post-radiation primary hypothyroidism was 41.4 % (range, 10 %–57 %). Multiple radiation dose-volume parameters were associated with post-radiation primary hypothyroidism, including the thyroid mean dose (Dmean), minimum dose, V25, V30, V35, V45, V50, V30–60, VS45 and VS60. Thyroid Dmean and V50 were the most frequently proposed dosimetric predictors. The pooled adjusted OR of thyroid volume on the risk of post-radiation primary hypothyroidism was 0.89 (95 % confidence interval, 0.85–0.93; p < 0.001) per 1 cc increment.

Conclusion

Post-radiation primary hypothyroidism is a common late complication after radiotherapy for HNC. Minimizing inadvertent exposure of the thyroid gland to radiation is crucial to prevent this late complication. Radiation dose-volume constraints individualized for thyroid volume should be considered in HNC radiotherapy planning.

Modern LINAC-based radiotherapy is safe and effective in the treatment of secretory and non-secretory pituitary adenomas

OBJECTIVE

Adjuvant radiotherapy (RT) can help achieve local tumor control (LC) and reduce hormonal overexpression for pituitary adenomas (PAs). Prior reports involved Gamma Knife or older LINAC techniques. We report on long-term outcomes for modern LINAC RT.

METHODS

Institutional retrospective review of LINAC RT for PAs with minimum 3 years MRI follow-up. Hormonal control defined as biochemical remission in absence of medications targeting hormone excess LC defined using RECIST on surveillance MRIs. Progression Free Survival (PFS) defined as time alive with LC and without return of or worsening hormonal excess from secretory PA. Kaplan-Meier method and Cox proportional hazard models used.

RESULTS

From 2003-2017, 140 patients with PAs (94 non-secretory, 46 secretory) were treated with LINAC RT (105 fractionated, 35 radiosurgery) with mFU of 5.35 years. Techniques included fixed gantry IMRT (51.4%), DCA (9.3%), and VMAT (39.3%). PFS at 5-years was 95.3% for secretory tumors and 94.8% for non-secretory tumors. Worse PFS associated with larger PTV on MVA (HR 2.87, 95% CI 1.01 - 8.21, p=0.049). Hormonal control at 5 years was 50.0% and associated with higher dose to the tumor (HR 1.05, 95% CI 1.02 -1.09, p=0.005) and number of surgeries (HR 1.74, 95% CI 1.05-2.89, p=0.032). Patients requiring any pituitary hormone replacement increased from 57.9% to 70.0% after radiotherapy.

CONCLUSION

Modern LINAC RT for patients with PAs was safe and effective for hormonal control and LC. Notably, no difference in LC was noted for functional versus non-functional tumors possibly due to higher total dose and daily image guidance.

High-dose radiation exposure and hypothyroidism: aetiology, prevention and replacement therapy

Without any doubt, high dose radiation exposure can induce hypothyroidism. However, there are open questions related to the mechanisms of its induction, corresponding dose thresholds and possible countermeasures. Therefore, this review addresses the aetiology, prevention and therapy of radiation induced hypothyroidism. External beam radiotherapy with several 10 Gy to the head and neck region and radioiodine therapy with several 100 Gy thyroid absorbed dose can destroy the thyroid gland and can induce autoantibodies against thyroid tissue. According to recent literature, clinical hypothyroidism is observed at threshold doses of ∼10 Gy after external beam radiotherapy and of ∼50 Gy after radioiodine therapy, children being more sensitive than adults. In children and adolescents exposed by the Chernobyl accident with mean thyroid absorbed doses of 500-800 mGy, subclinical hypothyroidism has been detected in 3%-6% of the cases with significant correlation to thyroid absorbed doses above 2.5 Gy. In case of nuclear emergencies, iodine thyroid blocking (ITB) is the method of choice to keep thyroid absorbed doses low. Large doses of stable iodine affect two different steps of internalization of radioiodine (transport and organification); perchlorate affecting the transport only may be an alternative to iodine. Administered before radioiodine incorporation, the effect of 100 mg iodide or more is still about 90% after 1 days, 80% after 2 days, and 50% or less after 3 days. If administered (too) late after exposure to radioiodine, the theoretically expected protective effect of ITB is about 50% after 6 h, 25% after 12 h, and about 6% after 24 h. In case of repeated or continuous exposure, repeated administration of 50 mg of iodide daily is indicated. If radiation-induced hypothyroidism cannot be avoided, thyroid hormone replacement therapy with individualized dosing and regular monitoring in order to maintain thyroid-stimulating hormone levels within the normal range ensures normal life expectancy.

An Underestimated Toxicity Radiation-Induced Hypothyroidism in Patients Multimodally Treated for Breast Cancer

Radiation therapy is part of the therapeutic arsenal for breast cancer, whether it is adjuvant treatment after lumpectomy or radical mastectomy, or it is used as a palliative option in the case of metastatic or recurrent disease. Significant advances in diagnostic and therapeutic stratification of breast cancers have significantly prolonged survival, even in the metastatic stage. Exposure of patients during the course of the disease in a multidisciplinary therapeutic approach including chemotherapy, hormone therapy, targeted anti-HER therapies or CDK4/6 inhibitors had led to improved survival but with the price of additional toxicity. Among them, hypothyroidism is a well-known consequence of external radiation therapy, especially in the case of cervical region irradiation, including supraclavicular and infra-clavicular nodal levels. In this situation, the thyroid gland is considered as an organ at risk (OAR) and receives a significant dose of radiation. Subclinical hypothyroidism is a common endocrine disorder characterized by elevated TSH levels with normal levels of FT4 (free T4) and FT3 (free T3), and as a late effect, primary hypothyroidism is one of the late effects that significantly affects the quality of life for patients with breast cancer receiving multimodal treatment. Hypothyroidism has a significant impact on quality of life, most often occurring as late clinical toxicity, secondary to thyroid irradiation at doses between 30 and 70 Gy. Dose-volume parameters of irradiation, gland function at the beginning of the treatment and associated systemic therapies may be factors that alter thyroid radio-sensitivity and affect thyroid gland tolerance. In the case of head and neck tumor pathology, in which doses of >50 Gy are routinely used, the thyroid gland is generally considered as an OAR, the rate of radio-induced hypothyroidism being estimated at rates of between 20% and 52%. For breast cancer, the thyroid is often neglected in terms of dosimetry protection, the rate of late dysfunction being 6–21%.

The impact of nutritional counseling on thyroid disorders in head and neck cancer patients after (chemo)radiotherapy: results from a prospective interventional trial

Objective

To analyze the impact of nutritional counseling on the development of hypothyroidism after (chemo)radiotherapy in head and neck cancer patients to propose a new normal tissue complication probability (NTCP) model.

Materials and methods

At baseline, at the end of (chemo)radiotherapy, and during follow-up, thyroid-stimulating hormone (TSH) with free thyroxin (fT3 and fT4), nutritional status, and nutrient intake were prospectively analyzed in 46 out of 220 screened patients. Patients received (chemo)radiotherapy within an intervention (individual nutritional counseling every 2 weeks during therapy) and a control group (no nutritional counseling).

Results

Overall median follow-up was 16.5 [IQR: 12; 22] months. Fourteen patients (30.4%) presented with hypothyroidism after 13.5 [8.8; 17] months. During (chemo)radiotherapy, nutritional status worsened in the entire cohort: body mass index (p < 0.001) and fat-free mass index (p < 0.001) decreased, calorie deficit (p = 0.02) increased, and the baseline protein intake dropped (p = 0.028). The baseline selenium intake (p = 0.002) increased until the end of therapy. Application of the NTCP models by Rønjom, Cella, and Boomsma et al. resulted in good performance of all three models, with an AUC ranging from 0.76 to 0.78. Our newly developed NTCP model was based on baseline TSH and baseline ferritin. Model performance was good, receiving an AUC of 0.76 (95% CI: 0.61–0.87), with a sensitivity of 57.1% and specificity of 96.9% calculated for a Youden index of 0.73 (p = 0.004; area = 0.5).

Conclusion

Baseline TSH and ferritin act as independent predictors for radiotherapy-associated hypothyroidism. The exclusion of such laboratory chemistry parameters in future NTCP models may result in poor model performance.

Recurrence of Lymph Node Micrometastases After Radiotherapy for Head and Neck Carcinoma: A Propensity Score-matched Study

BACKGROUND

The standard irradiation dose to the elective lymph node area (ELNA) in locally patients with advanced head and neck squamous cell carcinoma (LA-HNSCC) to control lymph node micrometastases (LN-MM) has not changed since it was empirically determined in the 1950s. We investigated the optimal irradiation dose for controlling LN-MM in ELNAs.

PATIENTS AND METHODS

The pattern of recurrence of LA-HNSCC was retrospectively evaluated in patients who underwent concurrent chemoradiotherapy with cisplatin or radiation therapy alone.

RESULTS

In total, 162 patients were enrolled. The median observation period was 34 months. No recurrence was found in ELNAs. After propensity score matching, a cisplatin dose of ≥200 mg/m ² yielded a significantly higher overall survival rate (p≤0.001) and locoregional control rate (p=0.034) than did a dose of <100 mg/m ² .

CONCLUSION

CCRT with a cisplatin dose of ≥200 mg/m ² can reduce the irradiation dose to 40-44 Gy at 2 Gy per fraction to control LN-MM.

Real-world safety and effectiveness of nivolumab for recurrent or metastatic head and neck cancer in Japan: a post-marketing surveillance

Background

On the basis of phase III CheckMate 141 results, nivolumab was approved for recurrent or metastatic head and neck cancer after undergoing platinum-containing chemotherapy in Japan. This post-marketing surveillance aimed to evaluate the safety and effectiveness of nivolumab for head and neck cancer in the real-world setting.

Methods

All patients with head and neck cancer who planned to receive nivolumab were centrally registered. This study monitored 607 patients for 6 months to assess nivolumab’s safety, especially treatment-related adverse events (TRAEs) of special interest, and effectiveness.

Results

TRAEs occurred in 36.1% patients, with no new safety signals. The most common TRAEs with grade ≥ 3 were interstitial lung disease (1.2%), diarrhea (0.8%), and hepatic function abnormal (0.7%). Meanwhile, thyroid dysfunction (10.2%), hepatic dysfunction (5.3%), and interstitial lung disease (4.1%) were the most common TRAE categories of special interest. Although the median time to the onset of each TRAE category of special interest was mostly 1–2 months, most of them occurred throughout the observation period; nonetheless, the majority of patients recovered or remitted. The 6-month survival rate was 55.9%.

Conclusion

Japanese patients with head and neck cancer treated with nivolumab in the real-world setting manifested no new safety signals.

Clinical Trial Registration

clinicaltrials.jp: JapicCTI-184071.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10147-021-01949-1.

MorbiNet Study: Hypothyroidism Comorbidity Networks in the Adult General Population

PURPOSE

Multimorbidity impacts quality of life. We constructed hypothyroidism comorbidity networks to identify positive and negative associations with other prevalent diseases.

METHODS

We analyzed data of 285 342 patients with hypothyroidism from 3 135 948 adults with multimorbidity in a population-based study in Catalonia, Spain, (period: 2006-2017). We constructed hypothyroidism comorbidity networks using logistic regression models, adjusted by age and sex, and for men and women separately. We considered relevant associations those with odds ratios (OR) >1.2 or <0.8 and P value < 1e-5 to identify coexistence greater (or smaller) than the expected by the prevalence of diseases. Multivariate models considering comorbidities were used to further adjust OR values.

RESULTS

The conditions associated included larynx cancer (adjusted OR: 2.48), congenital anomalies (2.26), thyroid cancer (2.13), hyperthyroidism (1.66), vitamin B12/folate deficiency anemia (1.57), and goiter (1.56). The network restricted to men had more connections (mental, cardiovascular, and neurological) and stronger associations with thyroid cancer (7.26 vs 2.55), congenital anomalies (5.11 vs 2.13), hyperthyroidism (4.46 vs 1.69), larynx cancer (3.55 vs 1.67), and goiter (3.94 vs 1.64). After adjustment for comorbidities, OR values were more similar in men and women. The strongest negative associations after adjusting for comorbidities were with HIV/AIDS (OR: 0.71) and tobacco abuse (0.77).

CONCLUSIONS

Networks show direct and indirect hypothyroidism multimorbidity associations. The strongest connections were thyroid and larynx cancer, congenital anomalies, hyperthyroidism, anemia, and goiter. Negative associations included HIV/AIDS and tobacco abuse. The network restricted to men had more and stronger associations, but not after adjusting for comorbidities, suggesting important indirect interactions.

Hypothyroidism and risks of cerebrovascular complications among patients with head and neck cancer after radiotherapy

BACKGROUND

Hypothyroidism (HT) and carotid artery stenosis (CAS) are complications of radiotherapy (RT) in patients with head and neck cancer (HNC). The impact of post-RT HT on CAS progression remains unclear.

METHODS

Between 2013 and 2014, HNC patients who had ever received RT and were under regular follow-up in our hospital were initially screened. Patients were categorized into euthyroid (EU) and HT groups. Details of RT and HNC were recorded. Total plaque scores and degrees of CAS were measured during annual extracranial duplex follow-up. Patients were monitored for CAS progression to > 50 % stenosis or ischemic stroke (IS). Cumulative time to CAS progression and IS between the 2 groups were compared. Data were further analyzed based on the use or nonuse of thyroxine of the HT group.

RESULTS

333 HNC patients with RT history were screened. Finally, 216 patients were recruited (94 and 122 patients in the EU and HT groups). Patients of the HT group received higher mean RT doses (HT vs. EU; 7021.55 ± 401.67 vs. 6869.69 ± 425.32 centi-grays, p = 0.02). Multivariate Cox models showed comparable CAS progression (p = 0.24) and IS occurrence (p = 0.51) between the 2 groups. Moreover, no significant difference was observed in time to CAS progression (p = 0.49) or IS (p = 0.31) among patients with EU and HT using and not using thyroxine supplement.

CONCLUSIONS

Our results did not demonstrate significant effects of HT and thyroxine supplementation on CAS progression and IS incidence in patients with HNC after RT.

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.

NTCP model for hypothyroidism after supraclavicular-directed radiation therapy for breast cancer

BACKGROUND AND PURPOSE

Hypothyroidism (HT) is a well-known complication of radiation (RT) that includes supraclavicular (SCV) fields. We analyzed breast cancer patients who received SCV-directed RT to evaluate predictors of HT and developed the first normal tissue complication probability (NTCP) model for HT specific to breast cancer patients.

MATERIALS AND METHODS

192 breast cancer patients received SCV-directed RT between 2007 and 2019 and met inclusion criteria. Individual dose-volume histograms were analyzed to determine thyroid volume within and outside specific isodose lines as well as minimum, mean, and maximum doses. Multivariable logistic regression was performed to assess potential clinical and treatment factors for the development of hypothyroidism. An NTCP model was created, and model validation was performed.

RESULTS

Thirty-seven patients (19.3%) developed HT following SCV-directed RT at a median 25 months (range: 2-83 months). Multivariable analysis revealed longer length of follow-up (p = 0.015) and larger thyroid volume receiving less than 20 Gy (CV20Gy[cc]; p = 0.045) were significant prognostic factors (p = 0.039). IMRT was not associated with an increased risk of hypothyroidism (p = 0.28) despite lower CV20Gy[cc] (p = 0.0002). On NTCP modeling, CV20Gy[cc] ≥ 8.5 cc was associated with a risk of HT < 15%. For smaller thyroids, mean dose and thyroid volume were found to be predictive of HT risk. Model validation demonstrated comparable performances between our model and other published models (AUC 0.69-0.72).

CONCLUSION

NTCP modeling within our patient cohort suggested that greater than 8.5 cc thyroid volume receiving less than 20 Gy may be a recommended dosimetric guideline to minimize HT risk in breast cancer patients receiving SCV-directed RT.

Effect of dose constraint on the thyroid gland during locoregional intensity-modulated radiotherapy in breast cancer patients

The aim of the present study was to compare radiation dose received by thyroid gland using different radiotherapy (RT) techniques with or without thyroid dose constraint (DC) for breast cancer patients. Computerized tomography (CT) image sets for 10 patients with breast cancer were selected. All patients were treated originally with opposite tangential field-in field (FinF) for the chest wall and anteroposterior fields for the ipsilateral supraclavicular field. The thyroid gland was not contoured on the CT images at the time of the original scheduled treatment. Four new treatment plans were created for each patient, including intensity-modulated radiotherapy (IMRT) and helical tomotherapy (HT) plans with thyroid DC exclusion and inclusion (IMRT_DC(-) , IMRT_DC(+) , HT_DC(-) , and HT_DC(+) , respectively). Thyroid DCs were used to create acceptable dose limits to avoid hypothyroidism as follows: percentage of thyroid volume exceeding 30 Gy less than 50% (V₃₀  < 50%) and mean dose of thyroid (TD_mean ) ≤ 21 Gy. Dose-volume histograms (DVHs) for TD_mean and percentages of thyroid volume exceeding 10, 20, 30, 40, and 50 Gy (V₁₀ , V₂₀ , V₃₀ , V₄₀ , and V₅₀ , respectively) were also analyzed. The D_mean of the FinF, IMRT_DC(-) , HT_DC(-) , IMRT_DC(+) and HT_DC(+) plans were 30.56 ± 5.38 Gy, 25.56 ± 6.66 Gy, 27.48 ± 4.16 Gy, 18.57 ± 2.14 Gy, and 17.34 ± 2.70 Gy, respectively. Median V₃₀ values were 55%, 33%, 36%, 18%, and 17%, for FinF, IMRT_DC(-) , HT_DC(-) , IMRT_DC(+) , and HT_DC(+) , respectively. Differences between treatment plans with or without DC with respect to D_mean and V₃₀ values were statistically significant (P < 0.05). When thyroid DC during breast cancer RT was applied to IMRT and HT, the TD_mean and V₃₀ values significantly decreased. Therefore, recognition of the thyroid as an organ at risk (OAR) and the use of DCs during IMRT and HT planning to minimize radiation dose and thyroid volume exposure are recommended.

Subsequent thyroid disorders associated with treatment strategy in head and neck cancer patients: a nationwide cohort study

BACKGROUND

We investigated the risk of thyroid disorders, namely hypothyroidism, thyrotoxicosis and thyroiditis, in head and neck cancer patients undergoing multimodal treatment.

METHODS

A cohort study design using Taiwan's National Health Insurance Research Database was used to assess head and neck cancer patients over 20 years old. The cohort was divided into one group who underwent primary tumor excision only (PTE) and another with additional neck dissection (PTE + ND). The tumor sites were stratified to estimate the tumor-site-specific risk of thyroid disorders. The effect of subsequent resurgery, radiotherapy (RT), chemotherapy (CT), and concomitant (CCRT) or sequential chemoradiation therapy (sequential CT+ RT) on the risk of thyroid disorders was explored.

RESULTS

For 1999-2012, 7460 patients who underwent PTE + ND and 3730 who underwent PTE were enrolled and followed-up until the end of 2013. There were 122 and 50 patients in the two groups, respectively, who developed thyroid disorders, with no statistical difference between the groups. Patients with hypopharyngeal, oropharyngeal, or laryngeal cancer in the PTE + ND group had a higher risk of thyroid disorders (adjusted HR: 1.50, 95% CI: 0.67-3.38) than those in the PTE group when adjusted for covariates and mortality. Patients who underwent subsequent RT (adjusted HR: 3.64, 95% CI: 1.05-2.77) and CCRT (adjusted HR: 1.70, 95% CI: 1.05-2.77) after PTE + ND had a significantly higher risk of thyroid disorders.

CONCLUSION

RT results in a major risk of subsequent thyroid disorders, and ND may exacerbate this effect. Physicians should monitor thyroid function from two years after treatment initiation, especially in patients who undergo ND and subsequent RT.

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.

Evidence on Effectiveness of Upper Neck Irradiation Versus Whole Neck Irradiation as Elective Neck Irradiation in Node-Negative Nasopharyngeal Cancer: A Meta-Analysis

Purpose

Nasopharyngeal carcinoma (NPC) is a central tumor with a rich lymphatic network and a propensity for bilateral cervical lymph node metastasis. There is an orderly pattern of lymph node involvement in NPC. There is no current standard for prophylactic neck irradiation in node-negative or limited retropharyngeal (RP) node–positive NPC. This study aims to synthesize the current evidence on upper neck irradiation (UNI) versus whole neck irradiation (WNI) as prophylactic neck irradiation in node-negative or limited RP node–positive NPC.

Materials and Methods

A search of relevant articles was done from 2000 to October 2015. Critical appraisal and meta-analysis of the eligible studies were undertaken to assess the effectiveness of UNI versus WNI as prophylactic neck irradiation in node-negative or limited involved RP node NPC.

Results

Only one randomized controlled trial investigated the use of prophylactic UNI versus WNI and showed no confirmed nodal relapse in both arms. Pooled analysis of four retrospective studies showed no significant difference in nodal recurrence, whether in-field or out-of-field recurrence. There was also no significant difference in terms of 5-year distant metastasis–free and overall survival.

Conclusion

In node-negative or limited RP node–positive NPC, the current evidence shows the possibility of treating only the upper neck (levels II, III, and VA) without compromising nodal control, distant metastasis, and overall survival. As a result of the scarcity of data, more randomized clinical trials are warranted in this subset of patients.

Revisiting the dose constraints for head and neck OARs in the current era of IMRT

Head and neck cancer poses a particular challenge in radiation therapy, whilst being an effective treatment modality it requires very high doses of radiation to provide effective therapy. This is further complicated by the fact that the head and neck region contains a large number of radiosensitive tissues, often resulting in patients experiencing debilitating normal tissue complications. In the era of intensity-modulated radiation therapy (IMRT) treatments can be delivered using non-uniform dose distributions selectively aimed at reducing the dose to critical organs-at-risk while still adequately covering the tumor target. Dose-volume constraints for the different risk organs play a vital role in one's ability to devise the best IMRT treatment plan for a head and neck cancer patient. To this end, it is pivotal to have access to the latest and most relevant dose constraints available and as such the goal of this review is to provide a summary of suggested dose-volume constraints for head and neck cancer RT that have been published after the QUANTEC reports were made available in early 2010.

A dosimetric study on radiation-induced hypothyroidism following intensity-modulated radiotherapy in patients with nasopharyngeal carcinoma

The objective of the present study was to investigate the association between thyroid gland-dosimetric parameters and hypothyroidism induced by intensity-modulated radiotherapy in patients with nasopharyngeal carcinoma (NPC). A total of 52 patients with NPC treated in the Department of Radiation Oncology of The Affiliated Hospital of Xuzhou Medical University, from May 2008 to December 2016 were retrospectively enrolled in the present study and divided into two groups based on thyroid function: The euthyroid and hypothyroid groups. The association between hypothyroidism and clinical or dosimetric parameters were analyzed. Females had a significantly increased probability of suffering from radiation-induced hypothyroidism (RIHT), compared with males (P=0.010). The occurrence of RIHT was significantly negatively associated with thyroid volume prior to radiotherapy (P=0.048). Furthermore, the mean dose (Dmean) and V50 in the hypothyroidism group were significantly increased, compared with the euthyroidism group (P=0.017 and P=0.023, respectively). During the treatment optimization period, dose constraints associated with the thyroid gland demonstrated a significantly protective effect on thyroid function compared with the unconstrained group (P=0.034). According to the receiver operating characteristic curves, the threshold value was 5,160 cGy for Dmean and 54.5% for V50. The 3-year cumulative incidence of RIHT was 67.8% when the Dmean value was >5,160 cGy and 44.6% when the Dmean was <5,160 cGy (log rank test, P=0.036). Furthermore, the 3-year cumulative incidence was 66.1% when the V50 was >54.5%, and 29.9% when the V50 was <54.5% (log rank test, P=0.025). In conclusion, RIHT is associated with radiation dose, particularly with Dmean and V50 of the thyroid gland. Dose constraints associated with the thyroid gland significantly reduced the incidence of hypothyroidism compared with the unconstrained group.

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.

Validation of previously reported predictors for radiation-induced hypothyroidism in nasopharyngeal cancer patients treated with intensity-modulated radiation therapy, a post hoc analysis from a Phase III randomized trial

This study aimed to validate previously reported dosimetric parameters, including thyroid volume, mean dose, and percentage thyroid volume, receiving at least 40, 45 and 50 Gy (V40, V45 and V50), absolute thyroid volume spared (VS) from 45, 50 and 60 Gy (VS45, VS50 and VS60), and clinical factors affecting the development of radiation-induced hypothyroidism (RHT). A post hoc analysis was performed in 178 euthyroid nasopharyngeal cancer (NPC) patients from a Phase III study comparing sequential versus simultaneous-integrated boost intensity-modulated radiation therapy. RHT was determined by increased thyroid-stimulating hormone (TSH) with or without reduced free thyroxin, regardless of symptoms. The median follow-up time was 42.5 months. The 1-, 2- and 3-year freedom from RHT rates were 78.4%, 56.4% and 43.4%, respectively. The median latency period was 21 months. The thyroid gland received a median mean dose of 53.5 Gy. Female gender, smaller thyroid volume, higher pretreatment TSH level (≥1.55 μU/ml) and VS60 < 10 cm3 were significantly associated with RHT in univariate analyses. Only pretreatment TSH ≥ 1.55 μU/ml and VS60 < 10 cm3 were significant predictors in multivariate analysis. Our results suggested that patients with pretreatment TSH ≥ 1.55 μU/ml should be cautious about the risk of RHT. The VS60 ≥ 10 cm3 is recommended for treatment planning.

Development of a normal tissue complication probability (NTCP) model for radiation-induced hypothyroidism in nasopharyngeal carcinoma patients

BACKGROUND

The objectives of this study were to build a normal tissue complication probability (NTCP) model of radiation-induced hypothyroidism (RHT) for nasopharyngeal carcinoma (NPC) patients and to compare it with other four published NTCP models to evaluate its efficacy.

METHODS

Medical notes of 174 NPC patients after radiotherapy were reviewed. Biochemical hypothyroidism was defined as an elevated level of serum thyroid-stimulating hormone (TSH) value with a normal or decreased level of serum free thyroxine (fT4) after radiotherapy. Logistic regression with leave-one-out cross-validation was performed to establish the NTCP model. Model performance was evaluated and compared by the area under the receiver operating characteristic curve (AUC) in our NPC cohort.

RESULTS

With a median follow-up of 24 months, 39 (22.4%) patients developed biochemical hypothyroidism. Gender, chemotherapy, the percentage thyroid volume receiving more than 50 Gy (V50), and the maximum dose of the pituitary (Pmax) were identified as the most predictive factors for RHT. A NTCP model based on these four parameters were developed. The model comparison was made in our NPC cohort and our NTCP model performed better in RHT prediction than the other four models.

CONCLUSIONS

This study developed a four-variable NTCP model for biochemical hypothyroidism in NPC patients post-radiotherapy. Our NTCP model for RHT presents a high prediction capability.

TRIAL REGISTRATION

This is a retrospective study without registration.

Postradiation hypothyroidism in head and neck cancers: A Department of Veterans Affairs single-institution case-control dosimetry study

We performed a case-control study to characterize the dose-volume relationship and other variables leading to hypothyroidism after head and neck (H&N) cancer radiation therapy (RT) in a homogenous Veterans Affairs (VA) population. All records of patients receiving RT for various H&N cancers at a single VA medical center between 2007 and 2013 (n = 143) were screened for post-RT thyroid stimulating hormone (TSH) levels (n = 77). The thyroid gland was contoured on each slice of the planning computed tomography scan when available (hypothyroid: n = 18; euthyroid > 2 years: n = 16), and dose-volume histograms based on physical dose and biologically equivalent dose (BED) were compared systematically to find the significant dose-volume thresholds that distinguish the patients who developed clinical hypothyroidism. Dosimetric and clinical variables were considered in univariate and multivariate analysis. Preirradiation prevalence of hypothyroidism was 8 of 143 (5.6%). After RT, 36 of 77 (47%) screened patients had abnormally high TSH, of which 22 of 36 (61%) had clinical hypothyroidism after 1.29 ± 0.99 years. The median follow-up durations were 3.3 years and 4.7 years for euthyroid and hypothyroid patients, respectively. Compared with the euthyroid cohort (n = 41), these hypothyroid patients displayed no significant difference in age, gender, primary tumor site, thyroid volume, hypertension, diabetes, or use of chemotherapy, surgery, or intensity-modulated radiation therapy (IMRT). They were more likely to have had stage 3 or 4 cancer than euthyroid patients (86.5% vs 73.2%, p = 0.01). The odds ratios of hypothyroidism for stage 3 + 4 cancers and V50Gy < 75% were 5.0 and 0.2, respectively (p < 0.05). Equivalent BED threshold of V75Gy₃ < 75% gave an odds ratio of 0.156 for developing hypothyroidism (p = 0.02). The prevalence of post-RT clinical hypothyroidism was relatively high for patients with H&N cancers and warrants routine surveillance, especially in those with higher stage malignancy. V50Gy < 75% may be a useful guideline to avoid hypothyroidism. We also show BED data which could be used for unconventionally fractionated schemes, and V75Gy₃ < 75% may be a useful guideline.

Systematic Review of Normal Tissue Complication Models Relevant to Standard Fractionation Radiation Therapy of the Head and Neck Region Published After the QUANTEC Reports

There has recently been an increasing interest in model-based evaluation and comparison of different treatment options in radiation oncology studies. This is partly driven by the considerable technical advancements in radiation therapy of the last decade, leaving radiation oncologists with a multitude of options to consider. In lieu of randomized trials comparing all of these different treatment options for varying indications, which is unfeasible, treatment evaluations based on normal tissue complication probability (NTCP) models offer a practical alternative. The Quantitative Analyses of Normal Tissue Effects in the Clinic (QUANTEC) effort, culminating in a number of reports published in 2010, provided a basis for many of the since-implemented dose-response models and dose-volume constraints and was a key component for model-based treatment evaluations. Given that 7 years have passed since the QUANTEC publications and that patient-reported outcomes have emerged as an important consideration in recent years, an updated summary of the published radiation dose-response literature, which includes a focus on patient-reported quality of life outcomes, is warranted. Here we provide a systematic review of quantitative dose-response models published after January 1, 2010 for endpoints relevant to radiation therapy for head and neck cancer, because these patients are typically at risk for a variety of treatment-induced normal tissue complications.

Nomogram for radiation-induced hypothyroidism prediction in nasopharyngeal carcinoma after treatment

OBJECTIVE

The aim of this study was to develop a nomogram for radiation-induced hypothyroidism (RHT) prediction.

METHODS

We collected data from 164 patients with nasopharyngeal carcinoma (NPC) in our previous prospective study. Biochemical hypothyroidism was defined as a serum thyroid-stimulating hormone level greater than the normal value. We collected both clinical and dose-volume factors. A univariate Cox regression analysis was performed to identify RHT risk factors. Optimal predictors were selected according to the least absolute shrinkage and selection operator (LASSO). We then selected the Cox regression models that best balanced the prediction performance and practicability to build a nomogram for RHT prediction.

RESULTS

There were 38 (23.2%) patients who developed RHT, and the median follow-up was 24 months. The univariate Cox regression analysis indicated that gender, minimum dose, mean dose (D_mean) and V₂₅-V₆₀ [V_x (%), the percentage of thyroid volume receiving >x Gy] of the thyroid were significantly associated with RHT. The variables of gender, receiving chemotherapy or not (chemo), D_mean and V₅₀ were selected using the LASSO analysis. A nomogram based on a three-variable (gender, chemo and V₅₀) Cox regression model was constructed, and its concordance index was 0.72. Good accordance between prediction and observation was showed by calibration curves in the probability of RHT at 18, 24 and 30 months.

CONCLUSION

This study built a nomogram for RHT in NPC survivors by analyzing both clinical and dose-volume parameters using LASSO. Thus, the individual dose constraint could be achieved in a visual format. Advances in knowledge: This study used LASSO to more accurately address the multicollinear problem between variables. The resulting nomogram will help physicians predict RHT.

Thyroid Function after Postoperative Radiation Therapy in Patients with Breast Cancer

Objective: The aim of this study was to assess thyroid function in breast cancer patients exposed to therapeutic external beam radiation. The focus was on possible progressive changes and any relationships between the incidence of primary hypothyroidism, the time required to become hypothyroid, and factors such as chemotherapy, hormonotherapy and immunotherapy. Materials and Methods: Seventy females undergoing 3D conformal and IMRT radiation therapy for breast cancers were enrolled in a non-randomized prospective study. The patients was divided into two groups: those after mastectomy or breast conserving surgery (BCS) were irradiated to a scar of the chest wall/breast and the ipsilateral supraclavicular and the axillary areas (supraclavicular radiotherapy group - SC-RT group – 32 patients) and the control group receiving adjuvant chest wall/breast RT only (BCT group - 38 patients).The total doses were 50.0 to 70 Gy in 5 to 7 weeks. The median follow-up term was 24 months (range, 1–40 months). Thyroid function was evaluated by measuring thyroid stimulating hormone (TSH), free thyroxine (fT4), and free triiodothyronine (fT3) levels. The minimum, maximum and mean thyroid gland doses for 20 Gy (V20) were calculated for all patients. Results: Statistically significant results were obtained for the SC-RT group. Two yearsa fter the end of RT the chance of an event was increased in 6% of the population (p=0.009) in the SC-RT group. In the BCT group no significance was noted. No statistically significant differences were found for V20, chemio-, immunotherapy and hormonotherapy or Ki67 values (p=0.12). No significant results were obtained for development of hypothyroidism and clinical factors (age, thyroid volume, treatment modalities). Conclusion: Radiotherapy is associated with a higher incidence of thyroid toxicity in breast cancer patients. Routine thyroid function monitoring should be recommended in such cases.