Thyroid function after radiotherapy and total larynbecômy in the treatment of carcinoma of the larynx

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.

Hypothyroidism and Wound Healing After Salvage Laryngectomy

BACKGROUND

Patients undergoing salvage laryngectomy are predisposed to radiation-induced hypothyroidism and impaired wound healing secondary to the tissue effects of prior treatment. The impact of hypothyroidism on postoperative wound healing is not established.

METHODS

A single-institution retrospective case series was performed. The inclusion criteria specified preoperatively euthyroid adults who underwent salvage laryngectomy with concurrent neck dissection between 1997 and 2015 for persistent or recurrent laryngeal squamous cell carcinoma after radiation or chemoradiation therapy (n = 182). The principal explanatory variable was postoperative hypothyroidism, defined as thyroid-stimulating hormone (TSH) higher than 5.5 mIU/L. The primary end points of the study were pharyngocutaneous fistulas and wounds requiring reoperation. Multivariate analysis was performed.

RESULTS

The fistula rate was 47% among hypothyroid patients versus 23% among euthyroid patients. In the multivariate analysis, the patients who experienced hypothyroidism in the postoperative period had a 3.6-fold greater risk of fistula [95% confidence interval (CI) 1.8-7.1; p = 0.0002]. The hypothyroid patients had an 11.4-fold greater risk for a required reoperation (24.4 vs 5.4%) than the euthyroid patients (95% CI 2.6-49.9; p = 0.001). The risk for fistula (p = 0.003) and reoperation (p = 0.001) increased with increasing TSH. This corresponds to an approximate 12.5% incremental increase in the absolute risk for fistula and a 10% increase in the absolute risk for reoperation with each doubling of the TSH.

CONCLUSION

Postoperative hypothyroidism independently predicts postoperative wound-healing complications. The association of hypothyroidism with fistula formation may yield opportunities to modulate wound healing with thyroid supplementation or to provide a biomarker of wound progression.

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.

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.

Acid thyroglobulin protease activities in human diseased thyroid glands

The lysosomal acid protease is thought to be a main enzyme in hydrolysis of thyroglobulin. The protease activity of lysosome-rich fractions of various diseased thyroid glands were assayed by the sensitive and reproducible method developed in our laboratory. They included 78 diseased thyroid glands; 37 thyrotoxic goitres, five irradiated thyroids, five Hashimoto's thyroiditis, one granulomatous thyroiditis, six multinodular goitres, 14 'cold' adenomas, four 'hot' adenomas with three paranodular tissues, and six carcinomas. Fifteen paranodular tissues of cold and solitary thyroid nodules were served as controls. The protease activities were significantly increased in thyroid tissues of thyrotoxic goitres, Hashimoto's thyroiditis, adenomas and adenocarcinomas. In thyrotoxic goitres, the protease activity correlated well with the mean area size of colloid follicles. The 'hot' adenomas had higher protease activity than 'cold' ones. The protease activity of multinodular goitres was nearly normal. Only the irradiated thyroid glands had low protease activities. Therefore the high protease activities in hyperfunctioning goitres seem to reflect hormone secretory activities. On the other hand, cold neoplastic goitres seem to have lysosomal protease activities which are not associated with thyroidal secretory process. The assay of acid protease activity will be useful to understand the pathophysiology of lysosomal system in diseased thyroid glands.

Hypothyroidism following treatment for head and neck cancer

One hundred ninety-six head and neck patients were studied to determine the effects of radiation therapy and surgery on thyroid function. Serum thyroid-stimulating hormone (TSH) levels were obtained as a screening test for primary hypothyroidism. Elevated TSH levels were found in 57 of the 196 patients (29.1%). The highest incidence of abnormal TSH values (66%) occurred in the group treated with combination radiation therapy and surgery, including partial thyroidectomy. TSH levels rose early in the posttreatment period with 60% of the abnormal values occurring within the first three posttreatment years. Posttreatment thyroid dysfunction was twice as common in women (48.6%) as in men (25.4%). When serum thyroxine levels by radioimmunoassay (T4RIA) were correlated with the elevated serum TSH levels, a similar pattern was seen with 65% of the patients in Group 3 having a decreased T4RIA level indicating overt hypothyroidism. Pretreatment levels of thyroid function including thyroid antibody studies should be established for all patients. Serial TSH levels should be done every three months during the first three posttreatment years and semiannually thereafter as long as the patient will return for follow-up care. All patients treated with combination radiation therapy and surgery who develop elevated TSH levels should be treated with thyroid replacement therapy. Patients receiving radiation therapy alone should receive replacement thyroid therapy if they develop a depressed T4RIA value or a pattern of gradually increasing TSH levels.

Thyroid function after radiotherapy and laryngectomy for carcinoma of the larynx

Total levels of thyroxine (T4) and thyroid-stimulating hormone (TSH) were measured in 37 patients who had previously had carcinoma of the larynx treated by radiotherapy and total laryngectomy with thyroid lobectomy. Ten percent of the patients had clinical features of hypothyroidism and 30% had total T4 levels below the lower limit of normal. A further 40% had results in the low normal range. Forty-four percent of patients had raised TSH levels, 90% of these having low or low normal T4 levels. The histology of the thyroid gland was normal in all 37 patients. Attention should be given to preserving intact the vasculature of the contralateral thyroid lobe whenever it is necessary to remove the ipsilateral thyroid lobe during a laryngectomy. Proper postoperative assessment of thyroid gland function is desirable in all these patients to identify those at risk of hypothyroidism and to avoid unnecessary morbidity.

Myxedema coma and inappropriate antidiuretic hormone secretion after deep neck irradiation: clinical implications and report of a case

A case report is presented in which myxedema coma and inappropriate antidiuretic hormone secretion developed as a result of radiation therapy and surgery to the neck area in a patient with recurrent metastatic squamous cell carcinoma of the floor of the mouth. Laboratory findings of low thyroxine level and the findings of persistent hyponatremia and hypoosmolality of serum in spite of persistent sodium loss in the urine were helpful in diagnosing the problem. Treatment included thyroid hormone replacement and fluid restriction resulting in complete reversal of her condition. We believe that patients with head and neck cancer who have undergone a course of radiation to the neck, and particularly when thyroid function might have been altered by previous subtotal thyroidectomy as part of a curative resection, should be carefully followed with periodic thyroid function assays and serum electrolytes with particular attention to serum sodium values.