Hypothyroidism following treatment for head and neck cancer

Incidence and complications of hypothyroidism postlaryngectomy: A systematic review and meta-analysis

BACKGROUND

Hypothyroidism is common postlaryngectomy and is associated with laryngectomy-specific complications. The objective of this study is to determine the incidence and predictors of hypothyroidism postlaryngectomy and its associated complications.

METHODS

Systematic review, data extraction, and meta-analyses were performed following the PRISMA protocol. Six databases were searched for studies reporting on postlaryngectomy thyroid status with incidence, risk factors, management, or complications.

RESULTS

Fifty-one studies with 6333 patients were included. The pooled incidence of postlaryngectomy hypothyroidism is 49% (CI 42%-57%). Subgroup analysis showed postlaryngectomy hypothyroidism rates significantly correlated with hemithyroidectomy and radiotherapy. Patients who underwent laryngectomy, hemithyroidectomy, and radiotherapy had a 65% (CI 59%-71%) rate of hypothyroidism; laryngectomy and hemithyroidectomy 46% (CI 33%-60%); laryngectomy and radiotherapy 26% (CI 19%-35%); and laryngectomy alone 11% (CI 4%-27%) (p < 0.001).

CONCLUSIONS

Laryngectomized patients with partial thyroidectomy or radiation therapy are at significant risk of postoperative hypothyroidism. Evidence-based protocols for early detection and (prophylactic) treatment should be established.

Incidence of Post Total Laryngectomy Hypothyroidism: Effects of Thyroid Gland Surgery and Post-Operative Radiotherapy

To record the incidence of hypothyroidism in patients after total laryngectomy, whether with or without postoperative radiation therapy and to analyze the effect of hemithyroidectomy for the development of hypothyroidism. A retrospective study included patients who underwent total laryngectomy (with or without hemithyroidectomy) between 2018 and 2021 for laryngeal carcinoma and/or received postoperative radiotherapy. Thirty-six (45%) of the 80 enrolled patients developed hypothyroidism after a median follow-up of 16 months. In this study, adjuvant radiation and central neck dissection were found to be significantly linked with developing post-operative hypothyroidism (p values: 0.001, 0.007, respectively). The incidence of hypothyroidism in patients treated for laryngeal carcinoma is high, especially after combination treatment of surgery and radiotherapy.

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.

Does thyroid-sparing total laryngectomy decrease the risk of hypothyroidism?

BACKGROUND

Thyroid lobectomy is recommended with total laryngectomy for laryngeal cancer in the National Comprehensive Cancer Network ('NCCN') guidelines. However, it is associated with a 32-89 per cent risk of hypothyroidism, with or without adjuvant radiotherapy.

OBJECTIVE

The study aimed to determine whether preserving the whole thyroid, compared to a single lobe, does indeed significantly lower the incidence of hypothyroidism in the setting of total laryngectomy.

METHOD

A retrospective study was conducted at Groote Schuur Hospital in Cape Town, South Africa.

RESULTS

Eighty-four patients met the inclusion criteria. The overall incidence of hypothyroidism was 45.2 per cent. The incidence of hypothyroidism was significantly reduced in patients who underwent thyroid-sparing total laryngectomy compared to hemithyroidectomy (p = 0.037). Adjuvant radiotherapy was associated with a higher incidence of hypothyroidism (p = 0.001).

CONCLUSION

Thyroid-preserving laryngectomy should be advocated in carefully selected patients with advanced laryngeal carcinoma, as it reduces the incidence of hypothyroidism.

Hypothyroidism is associated with worse outcomes of hepatocellular carcinoma patients after liver transplantation

Background/Aims

Hypothyroidism has been associated with hepatocellular carcinoma (HCC) incidence; however, the relationship between hypothyroidism and HCC patient outcomes is unclear. We investigated the impact of hypothyroidism on outcomes after liver transplantation for HCC.

Materials and Methods

We retrospectively studied HCC patients transplanted between January 2000 and December 2015. Hypothyroidism was defined as a thyroid‐stimulating hormone (TSH) level continuously greater than 5 mIU/L, a documented history of hypothyroidism, or treatment with thyroid hormone replacement therapy. Multivariate Cox regression was used to assess the impact of hypothyroidism on overall survival (OS) and recurrence‐free survival (RFS) adjusting for potential confounders. Subgroup analyses and interaction tests were conducted to compare the impact of hypothyroidism in different subgroups and assess for possible synergistic effects. Sensitivity analyses were performed among different cohorts to verify the stability of the results.

Results

A total of 343 HCC patients who underwent liver transplantation were included in the analysis. The primary analysis was conducted among 288 patients diagnosed with HCC prior to transplantation. Hypothyroidism was independently associated with worse OS and RFS, as was elevated TSH. The adjusted hazard ratio (AHR) of hypothyroidism was 2.45 (95% confidence interval [CI], 1.44‐4.18) for OS and 5.54 (2.36, 13.01) for RFS. The AHR of TSH for OS was 1.05 (1.02, 1.09) and 1.08 (1.03, 1.13) for RFS. No interaction was found among different subgroups categorized by etiology and comorbidity. The results were stable to sensitivity analyses.

Conclusion

Hypothyroidism is associated with poorer overall and recurrence‐free survival of HCC patients receiving liver transplantation. These results require validation.

Hypothyroidism in Carcinoma of the Tongue with Adjuvant Treatment

OBJECTIVE

The objective of this study was to evaluate the incidence of hypothyroidism with adjuvant treatment in oral tongue carcinoma patients treated primarily with surgery.

MATERIALS AND METHODS

A retrospective review was carried out to analyze hypothyroidism incidence and its relation to adjuvant treatment (radiation/radio-chemotherapy) in oral tongue carcinoma after the primary surgical ablation and neck dissection. Hypothyroidism was analyzed in relation with dose of radiation, gender, and adjuvant treatment modality.

RESULTS

The study analyzed the patients who were treated between January 2012 and June 2015. Among 705 patients with carcinoma of the tongue treated primarily with wide local excision and neck dissection, 383 received adjuvant treatment. A total of 215 patients received radiation, and 168 received concurrent radio-chemotherapy. Of 378 patients, 78 developed hypothyroidism during follow-up: 27 patients received concurrent radio-chemotherapy, and the remaining 51 received only radiation. Lower neck received 40-48 Gy in 2 patients, 50 Gy in 74 patients, and 60-70 Gy and concurrent radio-chemotherapy in 27 patients. Median follow-up was 32 months. Hypothyroidism occurred in 21.5% of patients with squamous cell carcinoma of the oral tongue. The minimum period to develop hypothyroidism was 3 months in this study. Gender and adjuvant treatment were not found to be significant for the incidence of hypothyroidism.

CONCLUSIONS

A significant number of patients with carcinoma of the tongue who receive adjuvant treatment will develop hypothyroidism, hence frequent monitoring of thyroid function is advised during follow-up.

Relationship of Gender and Smoking History in the Development of Hypothyroidism From Exposure to External Beam Radiation for Head and Neck Cancers

Background

Patients with head and neck cancers (HNCs) are often treated with external beam radiation therapy (XRT). Unfortunately this therapy is not without its unintended consequences. One of these side effects includes the development of radiation-induced hypothyroidism. Our study is designed to pay special attention to variables like gender and smoking history and analyze their relationship with the development of hypothyroidism.

Methods

Patients’ charts were reviewed over a period of 13 years from January 1, 2000 to November 30, 2013 to gather information on patients who had previously received XRTs for HNCs. We used the Tumor Registry Database at the University of Florida, College of Medicine in Jacksonville for this retrospective review. Patient characteristics were examined including age, gender, race/ethnicity and smoking history. Special attention was paid to the development of hypothyroidism (thyroid stimulating hormones > 5.0 with appropriate decrease in free serum T4) levels after exposure to XRT for HNCs. Results were then analyzed using the univariate statistical analysis which was done using the SAS software using a 0.05 alpha level of significance expressed in terms of odds ratio (OR) with 95% confidence intervals (CIs).

Results

We found a total of 1,116 patients in our database who have received XRTs for HNCs. Out of these 72 (6.45%) patients developed hypothyroidism. Out of 263 African American patients 20 (7.6%) had hypothyroidism, whereas 49 (6%) out of 819 white people had this outcome. As for gender 32 out of 341 females (9.4%) and 40 out of 775 males had hypothyroidism. Thirty-five out of 544 (6.4%) with no family history and 19 (2.4%) out of 205 (9.3%) with positive family history for cancer had the outcome too. Finally 43 (6.5%) out of 664 smokers and 17 (8.3%) out of 206 non-smokers were found to develop hypothyroid as well. Both groups were found to have homogenous average age at diagnosis. When the univariate analysis was conducted, the strongest predicting variable was gender as hypothyroid patients were 1.90 (95% CI 1.17 - 3.09) times more likely to be females, and these results were statistically significant with P value of 0.008. More patients tended to be African Americans with OR 1.21 (CI 0.822 - 1.78), had positive family history of cancer (negative family history had OR 0.67 (CI 0.38 - 1.21), and less likely to be smokers (OR 0.77 (0.43 - 1.38). However, race, family history of cancer and smoking history did not achieve any statistical significance as evident by the P values.

Conclusion

In our patient population, females were more likely to develop radiation-induced hypothyroidism.

V30 as a predictor for radiation-induced hypothyroidism: a dosimetric analysis in patients who received radiotherapy to the neck

INTRODUCTION

The purpose of this study is to evaluate the possible predictors of thyroid disorders after neck radiotherapy, with a focus on radiation dose-volume factors.

METHODS

Thyroid function was measured in 100 patients who had received radiotherapy to the neck, including the thyroid. All radiation-induced thyroid dysfunctions were determined with an endpoint of abnormal thyroid stimulating hormone (TSH), free triiodothyronine (fT3) and thyroxine (fT4) and thyroid peroxidase antibodies and (TPA). The total volume of the thyroid, mean radiation dose to the thyroid (Dmean) and thyroid volume percentage that received radiation doses of 10-50 Gy (V10-V50) were calculated in all patients. The evaluated risk factors for thyroid dysfunction included dose-volume parameters, sex, age, previous surgery, chemotherapy and comorbidity.

RESULTS

There were 52 patients with hypothyroidism and V30 (p = 0.03), thyroid volume (p = 0.01) and Dmean (p = 0.03) appeared to be correlated with hypothyroidism in univariate analysis. However, there was not association found in multivariate analysis for these factors.

CONCLUSIONS

Thyroid disorders after radiation therapy to the neck still represent a clinically underestimated problem. V30 may be a useful tool for evaluating the risk of hypothyroidism when determining an individual patient's treatment.

Thyroid dysfunction in patients treated with radiotherapy for neck

PURPOSE

The aim of the present study was to retrospectively evaluate the early and late changes in thyroid dysfunction after radiation therapy for head and neck cancer either with or without surgery.

PATIENTS AND METHODS

Sixty-three patients receiving neck irradiation including the thyroid gland were recruited in the study. Thirty-six patients had undergone either a functional or radical neck dissection, and radiotherapy was the primary treatment in 27 patients.

RESULTS

Of 63 patients, 24 (38%) were diagnosed with hypothyroidism (HT), 8 (12.7%) with clinical HT, and 16 (25.4%) with subclinical HT. The median time to the development of clinical HT was 15 months (range, 0-36 months) and subclinical HT was 3 months (range, 0-24 months). Eleven (17.5%) of the patients were diagnosed with subclinical hyperthyroidism. The median time to the development of the subclinical hyperthyroidism was 0 months (completion of radiation therapy) (range, 0-3 months). Univariate analyses of age, smoking history, neck RT dose, clinical stage, concurrent chemotherapy, and surgery failed to identify a clinically relevant risk factor for HT. Univariate analysis of clinical HT revealed that the elevated pre-radiation therapy thyroid-stimulating hormone level was significant factor (P = 0.021).

CONCLUSION

HT associated with head and neck irradiation. We recommend that thyroid function should be evaluated periodically in patients who have undergone neck radiation.

Hypothyroidism as a consequence of intensity-modulated radiotherapy with concurrent taxane-based chemotherapy for locally advanced head-and-neck cancer

PURPOSE

To conduct a retrospective review of 168 consecutively treated locally advanced head-and-neck cancer (LAHNC) patients treated with intensity-modulated radiotherapy (IMRT)/chemotherapy, to determine the rate and risk factors for developing hypothyroidism.

METHODS AND MATERIALS

Intensity-modulated radiotherapy was delivered in 33 daily fractions to 69.3 Gy to gross disease and 56.1 Gy to clinically normal cervical nodes. Dose-volume histograms (DVHs) of IMRT plans were used to determine radiation dose to thyroid and were compared with DVHs using conventional three-dimensional radiotherapy (3D-RT) in 10 of these same patients randomly selected for replanning and with DVHs of 16 patients in whom the thyroid was intentionally avoided during IMRT. Weekly paclitaxel (30 mg/m(2)) and carboplatin area under the curve-1 were given concurrently with IMRT.

RESULTS

Sixty-one of 128 evaluable patients (47.7%) developed hypothyroidism after a median of 1.08 years after IMRT (range, 2.4 months to 3.9 years). Age and volume of irradiated thyroid were associated with hypothyroidism development after IMRT. Compared with 3D-RT, IMRT with no thyroid dose constraints resulted in significantly higher minimum, maximum, and median dose (p < 0.0001) and percentage thyroid volume receiving 10, 20, and 60 Gy (p < 0.05). Compared with 3D-RT, IMRT with thyroid dose constraints resulted in lower median dose and percentage thyroid volume receiving 30, 40, and 50 Gy (p < 0.005) but higher minimum and maximum dose (p < 0.005).

CONCLUSIONS

If not protected, IMRT for LAHNC can result in higher radiation to the thyroid than with conventional 3D-RT. Techniques to reduce dose and volume of radiation to thyroid tissue with IMRT are achievable and recommended.

Thyroid Dysfunction after Combined therapy for Laryngeal Cancer: A Prospective Study

Objective

The purpose of this study was to assess the incidence of the thyroid dysfunction in a group of patients treated with laryngectomy and radiotherapy for larynx cancer and to analyze the risk factors related to the development of hypothyroidism.

Study Design

This was a prospective study conducted in a tertiary center hospital.

Subjects and Methods

Thyroid function tests have been applied to 75 patients treated with surgery and radiotherapy preoperatively, before radiotherapy, and postoperatively. Risk factors have been analyzed by carrying out a multivariate analysis.

Results

All the patients were men with the mean age of 59.4 and an average follow-up of 28.6 months. The incidence of hypothyroidism was 49.3 percent. The average time to detection of hypothyroidism was 6 months after the completion of treatment. Radiotherapy dose, type of laryngectomy, extent of neck dissection, implementation of thyroid lobectomy, and presence of thyroiditis in specimens were risk factors for thyroid dysfunction.

Conclusions

It is important to check the thyroid function periodically in these patients especially with risk factor to obtain early diagnosis and appropriate treatment.

Radiotherapy-associated Euthyroid Graves Ophthalmopathy following Floor-of-mouth Surgery: A Case Report

The thyroid gland is commonly included in the radiation field during treatment of nonthyroidal neoplastic disease of the head and neck. As a result, thyroid abnormalities sometimes occur following external irradiation. We report an unusual case of radiotherapy-associated Graves ophthalmopathy 5 months after adjuvant external irradiation of the head and neck in a euthyroid patient who had undergone wide local excision of squamous cell carcinoma from the floor of the mouth.

Thyroid dysfunction in laryngectomees—10 years after treatment

BACKGROUND

Hypothyroidism is 1 of the complications that follow treatment of various head and neck cancers. In the literature, reviews using different primary sites and differences in treatment modalities make comparison of post-treatment hypothyroidism not possible. The objective of this study was to evaluate the incidence of hypothyroidism in a homogenous group of patients who were treated with total laryngectomy and irradiation for laryngeal carcinoma and to assess the importance of different variables in the occurrence of hypothyroidism.

METHODS

A retrospective review of 147 total laryngectomy patients between 1993 and 2003 was carried out. Serum thyroxine level and free T4 levels were assessed in all patients. Hypothyroidism was classified as subclinical (increased thyroid-stimulating hormone and normal free T4 levels) and clinical (increased thyroid-stimulating hormone and decreased free T4 levels).

RESULTS

The results showed that the overall incidence of hypothyroidism was 49% (44% subclinical and 5% clinical). Hemithyroidectomy and advanced tumor staging were risk factors for the development of hypothyroidism in these patients (p < .05) with a relative risk of 2.1 (CI 95%, 1.4-3.1) and 1.3 (CI 95%, 1.1-1.6), respectively. During follow-up, 19.9% of patients developed hypothyroidism at 3 years, 38.6% at 6 years; at 10 year follow-up, 93.3% of them had hypothyroidism.

CONCLUSIONS

In conclusion, hypothyroidism is a frequent complication in patients treated with radiotherapy and total laryngectomy for laryngeal cancer, especially when treatment includes hemithyroidectomy. These patients should have their thyroid function evaluated periodically even 10 years after treatment.

Primary and Central Hypothyroidism After Radiotherapy for Head-and-Neck Tumors

PURPOSE

To investigate the incidence of radiotherapy (RT)-induced central and primary hypothyroidism regarding total dose, fractionation, and adjuvant chemotherapy.

METHODS AND MATERIALS

We retrospectively reviewed the data from 312 patients treated with RT for extracranial head-and-neck tumors between 1964 and 2000. The cervical lymph nodes were irradiated in 197 patients. The radiation doses to the thyroid gland and hypothalamic-pituitary axis were estimated by reconstructing the treatment plans.

RESULTS

Clinical central hypothyroidism (CH) was observed in 17 patients (5.4%); the median clinical latency was 4.8 years. Clinical primary hypothyroidism (PH) was observed in 40 patients (20.3%); the median clinical latency was 3.1 years. Multivariate analysis of clinical CH revealed that fractionation, adjuvant chemotherapy, and total dose to the pituitary were not significant. Multivariate analysis of clinical PH revealed that the total dose to the thyroid (p = 0.043) was significant, but adjuvant chemotherapy, age, and gender were not. Of the patients tested for hypopituitarism, 14 (20.3%) of 69 demonstrated subclinical CH and 17 (27.4%) of 62 demonstrated subclinical PH. The 5-year and 10-year rates of freedom from clinical CH and PH were 97% and 87% and 68% and 67%, respectively. Of the patients tested, the 5-year and 10-year rates of freedom from subclinical CH and PH were 91% and 78% and 71% and 71%, respectively.

CONCLUSION

Clinical and subclinical manifestations of late radiation toxicity were observed in the thyroid and hypothalamic-pituitary axis. Although CH did not indicate a dependence on fractionation, adjuvant chemotherapy, or total dose to the pituitary, PH showed a dependence on the total dose to the thyroid gland.

Hypothyroidism when the thyroid is included only in the low neck field during head and neck radiotherapy

OBJECTIVE

The minimum dose required to electively irradiate all of part of the low neck for squamous cell carcinoma of the oropharynx is 50 Gy in 25 fractions or its radiobiological equivalent. The purpose of our study is to determine the incidence of hypothyroidism when the thyroid is treated only in the low-neck radiotherapy (RT) field to approximately 50 Gy.

METHODS AND MATERIALS

390 patients with oropharyngeal carcinoma received RT between 1990 and 2000, had no prior thyroid disease or surgery, and had RT involving the standard anterior low-neck field including the thyroid with a dose equivalent to 50 Gy at 2Gy/fx with or without a boost to a portion of the field to 60 to 70 Gy. The end point was hypothyroidism defined as thyroid stimulating hormone (TSH) above the upper limit of the normal range.

RESULTS

As we did not routinely monitor TSH during this study, it was obtained in 169 of 390 patients. Median follow-up on all 390 patients was 6.1 years. The incidence of hypothyroidism was calculated for 2 groups: 169 patients with TSH data and the total population of 390 patients. For both analyses, patients were censored at last follow-up if the TSH level was normal, or if TSH was not checked. The incidence of hypothyroidism at 5 years was 31% for all 390 patients and 54% for the subset of 169 patients with TSH data. Adjuvant chemotherapy and/or planned neck dissection may be associated with a small increased risk of hypothyroidism.

CONCLUSIONS

Including the thyroid in the low-neck field to 50 Gy results in hypothyroidism in 30% to 50% of patients at 5 years, suggesting that the threshold for this complication is <50 Gy.

Thyroid Function Should Be Monitored Following Radiotherapy to the Low Neck

The purpose of this study was to determine whether the incidence of hypothyroidism following radiotherapy (RT) to the low neck is high enough to justify the routine monitoring of thyroid function in asymptomatic patients. A retrospective study of 504 patients with head and neck cancer whose RT fields included the thyroid gland was conducted. Patients were treated either with definitive or postoperative RT. Hypothyroidism was defined as a thyroid stimulating hormone (TSH) level > or =4.5 mIU/L, regardless of whether the patient had clinical symptoms. Of the 504 total patients, 206 had a serum TSH level checked at some point posttreatment. If we assume that patients who had no data did not have hypothyroidism, the actuarial freedom from hypothyroidism in the entire group was 78% at 5 years and 51% at 10 years. Of the 206 patients who had a documented posttreatment TSH, the actuarial freedom from hypothyroidism was 58% at 5 years and 26% at 10 years. Univariate analysis and multivariate analysis confirmed treatment modality to be a significant predictive factor. Definitive initial surgery that removed part of the thyroid gland increased the risk of developing hypothyroidism. Overall stage was also predictive on multivariate analysis. Head and neck irradiation results in biochemical hypothyroidism in at least 50% of patients. Thyroid function should be tested on a regular basis following RT to the low-neck region. Serum TSH should be checked every 6 months for the first 5 years and yearly thereafter. Thyroid hormone replacement should be initiated in any patient with a TSH of more than 4.5 mIU/L.

Long-term incidence of hypothyroidism after radiotherapy in patients with head-and-neck cancer

PURPOSE

To determine the long-term incidence of postirradiation hypothyroidism (HT) in patients with head-and-neck cancer.

METHODS AND MATERIALS

The incidence of overt HT was assessed prospectively in 391 patients with nonthyroid head-and-neck cancer admitted for radiotherapy (RT) consecutively between 1990 and 1996. Eighty-three patients were excluded from the analysis because of known thyroid disease before treatment (n = 27), no RT was given (n = 15), or inadequate follow-up (n = 41). Overt HT was defined as increased thyroid-stimulating hormone (TSH) in combination with decreased fT4/T4 or in combination with initiation of thyroxine replacement therapy.

RESULTS

With a median follow-up of 4.2 years (range, 3 months to 10.9 years) for 308 evaluable patients, the 5- and 10-year Kaplan-Meier actuarial risks of HT were 20% and 27%, respectively. The median time until development of HT was 1.8 years (3 months to 8.1 years). Multivariate analysis showed that patients with bilateral RT to the neck had a higher risk of HT in comparison with unilateral neck RT (relative hazard, 0.37; p = 0.02). The addition of surgery to RT increased the overall risk of HT (p < 0.001); and if surgery involved the thyroid gland, the relative hazard was 4.74 (p < 0.001). For an elevated pre-RT TSH value, the relative hazard was 1.58 (p < 0.001).

CONCLUSION

The incidence of overt HT after locoregional RT for nonthyroid head-and-neck cancer continues to increase with time, even after long-term follow-up. We recommend life-long TSH testing in these patients.

Radiotherapy-induced thyroid disorders

Despite their specific functional consequences, radiotherapy-induced thyroid abnormalities remain under-estimated and underreported. These sequelae may include primary or central hypothyroidism, thyroiditis, Graves' disease, euthyroid Graves' ophthalmopathy, benign adenomas, multinodular goitre and radiation-induced thyroid carcinoma. Primary hypothyroidism, the most common radiation-induced thyroid dysfunction, affects 20-30% of patients administered following curative radiotherapy to the neck region, with approximately half of the events occurring within the first 5 years after therapy. The relative risk of radiation-induced cancer (mainly well-differentiated tumours) is 15-53-fold higher than in non-irradiated population. The aetiology of radiation-induced thyroid injury includes vascular damage, parenchymal cell damage and auto-immune reactions. Total radiotherapy dose, irradiated volume of the thyroid gland, and the extent of prior thyroid resection are among the most important factors associated with the risk of hypothyroidism. The contribution of other treatment modalities (chemotherapy, endocrine therapy) as well as patient- and tumour-related factors is less clear. Reduction in radiation dose to the thyroid gland and hypothalamic/pituitary complex should be attempted whenever possible. New radiotherapy techniques, such as stereotactic radiosurgery, three-dimensional conformal irradiation, intensity modulated radiotherapy and proton therapy allow generally better dose distribution with lower dose to the non-target organs. The diagnostic approach to thyroid radiation injury includes baseline thyroid function assays in all patients undergoing thyroid or parasellar irradiation. Recommended follow-up procedures include at least annual evaluation with a history for symptoms of thyroid dysfunction, clinical examination, and measurement of thyroid hormones and thyrotropin. Management of overt hypothyroidism is based on hormone replacement therapy. Thyroid hormone therapy is also recommended in cases of subclinical hypothyroidism. Treatment of other radiation-induced thyroid disorders (thyroiditis, Graves' disease, thyroid cancer) is similar to that employed in spontaneously occurring conditions. Further improvements in radiotherapy techniques and progress in endocrine diagnostics and therapy may allow better prevention and management of radiation-related thyroid injury.

Hypothyroidism: a frequent event after radiotherapy and after radiotherapy with chemotherapy for patients with head and neck carcinoma

BACKGROUND

The incidence of hypothyroidism was assessed retrospectively from a data base of 155 patients with head and neck carcinoma who were treated at the Cleveland Clinic Foundation between 1990 and 1997.

METHODS

One hundred patients were randomized between radiotherapy (RT) (66-72 grays in single daily fractions) and RT with concurrent chemotherapy (CT) using 5-fluorouracil and cisplatin. An additional 55 patients received RT and CT without randomization. Primary site surgery was performed for tumor persistence or recurrence and included a thyroidectomy in nine patients. These nine patients, along with three patients who had hypothyroidism prior to treatment, were excluded from the analysis. At regular intervals after the completion of treatment, all patients were evaluated for the development of hypothyroidism, defined as a serum thyroid-stimulating hormone (TSH) level > 5.5 microU/mL.

RESULTS

With a median follow-up for 143 evaluable patients of 4.4 years (range, 1.5-9.2 years), the 5-year Kaplan-Meier projected incidence rate of hypothyroidism was 48%, and the 8-year projected incidence rate was 67%. The median time to the development of hypothyroidism was 1.4 years (range, 0.3-7.2 years). The likelihood of developing hypothyroidism could not be predicted according to age, gender, primary site, tumor or lymph node status, overall stage, RT dosage to the primary site or to the neck, or inclusion of CT in the treatment plan. Only race proved predictive, with no African-American patients developing hypothyroidism (P = 0.02).

CONCLUSIONS

The authors conclude that the incidence rate of hypothyroidism after patients undergo RT for head and neck carcinoma is higher than generally reported and that TSH screening after treatment appears justified.

Pretreatment prevalence of hypothyroidism in patients with head and neck carcinoma

BACKGROUND

Hypothyroidism in the normal population age > 60 years is encountered in the range of 0.5-5% clinically, and 5-20% have subclinical hypofunction. Hypothyroidism is recognized as a common complication of treatment in patients with head and neck carcinoma (HNC) and is reported in up to 75% of patients who receive combined treatment. Surprisingly, base-line pretreatment measurements of thyroid function in large series of patients have not been reported.

METHODS

Serum thyroid-stimulating hormone, free T4, and total T3 levels were recorded in 110 patients with nonthyroid HNC prior to treatment in a prospective, controlled study.

RESULTS

The mean patient age (+/- standard deviation) was 65 years +/- 13.8 years, and 82% of patients had squamous cell carcinoma. A diagnosis of hypothyroidism already was established in 4.5% of patients, and subclinical hypothyroidism was discovered in an additional 6.4% of patients. Sixteen patients had other equivocal anomalies in thyroid function and were referred for further endocrine evaluation. No patients with formerly unrecognized clinical hypothyroidism were found.

CONCLUSIONS

Hypothyroidism in patients with head and neck carcinoma in Israel corresponds with the reported incidence in the general population. Hypothyroidism after treatment for head and neck carcinoma stems from the effects of treatment. The need for pretreatment evaluation of thyroid function should be considered.

Risk factors associated with hypothyroidism after laryngectomy

Hypothyroidism is a well-documented complication after treatment of head and neck cancer and is particularly significant among patients undergoing laryngectomy. The objective of this study was the identification of factors associated with the development of hypothyroidism in this population. Records of 136 patients treated with laryngectomy were retrospectively reviewed in an attempt to define a risk factor profile for patients in whom hypothyroidism is most likely to develop after laryngectomy. The Cox proportional hazards model was used to identify factors significantly related to an increased risk for development of hypothyroidism. The actuarial method was used to estimate the period of greatest risk for the development of hypothyroidism. Increased risks were found for patients who were female (P = 0.0049), received preoperative radiation therapy (P = 0.0022), had invasion of the thyroid gland by tumor (P = 0.0003), had presence of cervical metastases (P = 0.0022), and had postoperative fistula (P = 0.0095). From the actuarial method, we estimated that the period of time when patients were at greatest risk for development of hypothyroidism was between 0 and 14 months after surgical intervention. Wound complications were twice as frequent in hypothyroid patients. Perioperative awareness of risk factors associated with the development of hypothyroidism in patients undergoing laryngectomy allows for early recognition and management of hypothyroidism and may reduce the number of complications related to wound healing and fistula.

Thyroid dysfunction following combined therapy for laryngeal carcinoma

The thyroid function of 27 patients who previously had carcinoma of the larynx treated by total laryngectomy with thyroid lobectomy was studied by measuring levels of thyroxine (T4) and thyroid stimulating hormone (TSH). Twenty-two of these patients also received external beam radiotherapy. Abnormal results were found in 45% (10 patients) of those who received combined therapy. Clinical hypothyroidism developed in two patients (9%) and subclinical hypothyroidism (elevated TSH) was seen in eight patients (36%). Eighty-eight per cent of those patients with subclinical hypothyroidism had low or low normal T4 levels. All the patients treated with surgery only had normal thyroid function. To prevent hypothyroidism and identify those at risk of developing hypothyroidism, post-operative testing of thyroid function should be carried out on a routine basis in patients receiving combined therapy for laryngeal cancer. In addition we recommend that patients with subclinical hypothyroidism who have had combined treatment should be treated with thyroxine to prevent the complications of this condition.

Hypothyroidism in head and neck cancer patients: experimental and clinical observations

Damage to the thyroid gland may occur in patients undergoing treatment for head and neck neoplasms. This injury may result from damage incurred during surgery, from radiation therapy, or a combination of the two. Development of hypothyroidism is often insidious with potential harmful effects. An experimental study was performed to study the effects of hypothyroidism in pigs whose skin closely approximates that of the human. Wound tensile strength and flap necrosis were studied in the hypothyroid animal treated by surgery, radiation, and a combination of the two. The results of this study indicate that hypothyroidism alone has no significant unfavorable impact on wound tensile strengths or flap survival. When combined with preoperative radiation, however, there are statistically significant deleterious effects on both wound tensile strengths and flap survival. Histologically, collagen fibers within the wound appear shorter and thinner, which probably accounts for decreased wound tensile strengths. A clinical review of 62 head and neck cancer patients was also conducted. Within the study group, 10% of patients developed abnormally low thyroxine measurements, whereas 15% developed high thyroid-stimulating hormone levels as the only evidence of early primary hypothyroidism. Hypothyroidism was not statistically related to tumor size, nodal status, clinical staging, or treatment group (surgery alone, radiation alone, or combination surgery and radiation). A previously unreported finding is that patients who develop a second primary tumor are significantly at risk for developing hypothyroidism. All patients diagnosed with a head and neck cancer should undergo baseline thyroid function testing, including measurement of TSH, and have serial repeat testing after treatment. Thyroid function determination should be mandatory in patients undergoing oncologic salvage procedures or treatment of a second primary tumor.

Thyroid dysfunction after radiation therapy in head and neck cancer patients

INTRODUCTION

The reported incidence of hypothyroidism following surgery and/or radiation therapy for head and neck cancer varies widely. Most patients undergo thyroid lobectomy during laryngectomy. Standard radiation treatment portals often include the thyroid gland. The insidious development of hypothyroidism may be misdiagnosed. This study examines the incidence of thyroid dysfunction in the setting of head and neck cancer therapy.

MATERIALS AND METHODS

Thyroid function tests were performed on 100 consecutive patients treated in the head and neck tumor clinic. Statistical inferences on proportions were made using chi-square analysis.

RESULTS

Therapy included surgery only (10 patients), radiation therapy only (28 patients), and combined therapy (62 patients). These patients experienced thyroid dysfunction in 0%, 29%, and 45% of individuals respectively. These differences were statistically significant (P < .05). The highest rate of dysfunction (69%) was associated with patients undergoing laryngectomy and radiation therapy. When laryngectomy was not performed, thyroid dysfunction occurred in 28%.

CONCLUSION

The likelihood of thyroid dysfunction after radiation therapy is high particularly when combined with surgery in which thyroid lobectomy is performed and the contralateral lobe is potentially devascularized. These results suggest that radiation therapy is a primary factor in alteration of thyroid function. We recommend that routine thyroid function testing be part of follow-up of all head and neck cancer patients.

Thyroid-stimulating hormone levels after radiotherapy and combined therapy for head and neck cancer

Sixty-eight patients were studied prospectively with serial thyroid-stimulating hormone (TSH) levels after radiotherapy for head and neck neoplasms. Overall, 57% of the patients developed elevated TSH levels. Excluding patients with less than 2 years follow-up, 85% developed an elevated TSH. Ninety-two percent of patients treated with partial thyroidectomy and radiotherapy developed an elevated TSH. Most TSH elevations occurred within 1 year of treatment. The dose of radiotherapy used and the performance of hemithyroidectomy were related to the development of elevated TSH levels (p less than 0.05). The performance of radical neck dissection, gender, hyperfractionated radiotherapy and the use of chemotherapy were not related to the development of an elevated TSH (p greater than 0.05).

Hypothyroidism following radiotherapy for head and neck cancer

Hypothyroidism is not commonly considered a complication of radiotherapy for head and neck cancer. A series of 96 patients treated with radiotherapy alone or combined with surgery for head and neck cancer was retrospectively studied. All patients had radiation ports that included the thyroid gland. Hypothyroidism after radiotherapy was documented in 26% of all patients. The majority of patients had subclinical hypothyroidism manifested by elevated thyroid-stimulating hormone (TSH) levels. The incidence of hypothyroidism dramatically increased to 65% when radiotherapy was combined with surgery that included a partial thyroidectomy. In addition, we report the unusual occurrence of massive head, neck, and hypopharyngeal edema caused by severe hypothyroidism in two patients. We advocate routine monitoring of head and neck cancer patients for hypothyroidism after radiotherapy involving the thyroid gland and recommend levothyroxine replacement therapy for subclinical hypothyroidism.

Pharyngeal fistulas in postoperative hypothyroid patients

Hypothyroidism is a well-recognized complication of combined treatment for head and neck cancer. We discuss four patients who developed pharyngeal fistulas after total laryngectomy and preoperative (one patient) or postoperative (three patients) radiation therapy. The fistulas were refractory to conservative and surgical repair. Once the existence of hypothyroidism was established, immediate substitution therapy resulted in rapid healing of the fistulas and marked improvement of the patients' general condition. Few clinical reports exist on postoperative hypothyroidism and wound healing complications. Experimental work shows delay and impairment of wound healing in hypothyroid animals as opposed to hyperthyroid ones, in which wound healing was accelerated. Suspicion is warranted in patients after treatment for head and neck cancer when they exhibit even minimal symptoms of hypothyroidism or develop postoperative complications refractory to conservative treatment.

Indications for performing hemithyroidectomy for tumors requiring total laryngectomy

To determine the necessity of performing a hemithyroidectomy in patients who require a total laryngectomy, the pathologic reports and clinical courses of 261 patients who underwent total laryngectomy were reviewed. Twenty-four percent of the specimens demonstrated transcartilaginous invasion, with the highest incidences occurring in glottic (31 percent) and subglottic (60 percent) tumors. Epidermoid tumor invading the thyroid gland occurred in 5 percent of the specimens. All of these showed invasion by direct extension, were palpable at the time of surgery and were associated with transcartilaginous invasion. Ninety percent of these tumors were primarily glottic or subglottic and 70 percent demonstrated subglottic extension greater than 1.5 cm. Furthermore, the prognosis of patients with tumorous invasion of the thyroid gland was dismal, with local recurrence or distant metastasis occurring within 10 months of curative resection. In patients who had laryngectomies, hypothyroidism was found in 70 percent of those who underwent radiotherapy and hemithyroidectomy, in 38 percent of those who underwent radiotherapy alone, in 23 percent of those who underwent hemithyroidectomy alone, and in 20 percent of those who did not undergo hemithyroidectomy or radiotherapy. Based on these results, we advocate ipsilateral or total thyroidectomy for palpably suspicious thyroid glands seen intraoperatively, subglottic tumors, glottic tumors with more than 1 cm of subglottic extension, T4 endolaryngeal tumors with transcartilaginous invasion, and T4 pyriform sinus tumors.