Thyroid dysfunction after mantle irradiation of Hodgkin's disease patients

Radiation-related thyroid autoimmunity and dysfunction

The thyroid gland is vulnerable not only to external radiation but also to internal radiation, because the thyroid cells can incorporate radioactive iodine when synthesizing thyroid hormones. Since radiation-induction of thyroid neoplasia, including thyroid cancer, is well recognized, the data on radiation-related thyroid autoimmunity and dysfunction are summarized and reviewed. High-dose irradiation, irrespective of being external or internal, is strongly associated with a risk of hypothyroidism (with the prevalence ranging from 2.4% to 31%) and of Graves' hyperthyroidism (with the prevalence being up to 5%). It is easy to understand that high-dose irradiation induces hypothyroidism with some frequency, because high-dose irradiation destroys the thyroid gland. On the other hand, the basis for development of hyperthyroidism is mechanistically unclear, and it is merely speculative that autoantigens may be released from damaged thyroid glands and recognized by the immune system, leading to the development of anti-thyrotropin receptor antibodies and Graves' hyperthyroidism in subjects who are immunologically predisposed to this ailment. In contrast, the data on moderate to low-dose irradiation on thyroid autoimmunity and dysfunction are inconsistent. Although it is difficult to draw a definitive conclusion, some data may suggest a transient effect of moderate- to low-dose irradiation on hypothyroidism and autoimmune thyroiditis, implying that the effect, if it exists, is reversible. Finally, no report has shown a statistically significant increase in the prevalence of moderate- to low-dose irradiation-induced Graves' hyperthyroidism.

Thyroid abnormalities in survivors of childhood cancer

OBJECTIVE

To investigate the late side effects of childhood cancer therapy on the thyroid gland and to determine the risk factors for development of thyroid disorder among childhood cancer survivors.

METHODS

One hundred and twenty relapse-free survivors of childhood cancer (aged 6-30 years) were included in this study. The diagnoses of patients were lymphoma, leukemia, brain tumor, rhabdomyosarcoma and nasopharyngeal carcinoma (NPC). The patients were divided into two groups depending on the treatment: group 1-chemotherapy (ChT) only (n=52) and group 2-combination therapy of ChT + radiotherapy (RT) (head/neck/thorax) (n=68). Thyroid function tests, urinary iodine levels, and thyroid gland ultrasound examinations were evaluated in both groups.

RESULTS

Incidence of thyroid disease was 66% (n=79) in the survivors. The thyroid abnormalities were: hypothyroidism (HT) (n=32, 27%), thyroid nodules (n=27, 22%), thyroid parenchymal heterogeneity (n=40, 33%), autoimmune thyroiditis (n=36, 30%), and thyroid malignancy (n=3, 2%). While the incidence of HT and thyroid nodules in group 2 was significantly higher than in group 1, the incidence of thyroid parenchymal heterogeneity and autoimmune thyroiditis was similar in the two patient groups. HT and thyroid malignancy were seen only in group 2. In multivariate logistic regression analysis, a history of Hodgkin lymphoma (HL), brain tumor and NPC, as well as cervical irradiation and 5000-5999 cGy doses of radiation were found to constitute risk factors for HT. History of HL and 4000-5999 cGy doses of radiation were risk factors for thyroid nodules. Head/neck irradiation and treatment with platinum derivatives were risk factors for autoimmune thyroiditis. In univariate analysis, a history of NPC, cervical + nasopharyngeal irradiation, and treatment with platinum derivatives were risk factors for thyroid parenchymal heterogeneity.

CONCLUSION

Our results indicate that there is especially an increased risk of HT and thyroid nodules in patients treated with combination therapy of ChT with head/neck/thorax RT. Although chemotherapeutic agents per se do not seem to cause HT, longer follow-up is needed to assess whether or not there is an increased risk for autoimmune thyroiditis and thyroid parenchymal heterogeneity after antineoplastic therapy.

Risk factors for radiation-induced hypothyroidism: a literature-based meta-analysis

BACKGROUND

A systematic overview and meta-analysis of studies reporting data on hypothyroidism (HT) after radiation therapy was conducted to identify risk factors for development of HT.

METHODS

Published studies were identified from the PubMed and Embase databases and by hand-searching published reviews. Studies allowing the extraction of odds ratios (OR) for HT in 1 or more of several candidate clinical risk groups were included. A meta-analysis of the OR for development of HT with or without each of the candidate risk factors was performed. Furthermore, studies allowing the extraction of radiation dose-response data were identified for a meta-analysis of the dose-response curve.

RESULTS

Female gender (OR = 1.6; 95% confidence interval [CI], 1.3-1.9; P < .00001), surgery involving the thyroid gland (OR = 8.3; 95% CI, 5.7-12.0; P < .00001), or other neck surgery (OR = 1.7; 95% CI, 1.16-2.42; P = .006) were associated with a higher risk of HT. Caucasians were at higher risk of HT than African Americans (OR = 4.8; 95% CI, 2.8-8.5; P < .00001). The data showed association between lymphangiography and HT but with evidence of publication bias. There was a radiation dose-response relation with a 50% risk of HT at a dose of 45 Gy but with considerable variation in the dose response between studies. Chemotherapy and age were not associated with risk of HT in this analysis.

CONCLUSIONS

Several clinical risk factors for HT were identified. The risk of HT increases with increasing radiation dose, but the specific radiation dose response varies between the studies. The most likely cause of this heterogeneity is differences in follow-up between studies.

Are We Improving the Long-Term Burden of Hodgkin's Lymphoma Patients with Modern Treatment?

The cure rate of patients who have Hodgkin's lymphoma (HL) amounts to 80% or more because of risk-adapted treatment using modern chemotherapy and radiotherapy schedules. In this article we describe important late effects after treatment of HL and how we expect the long-term burden of patients who have HL to change applying modern treatments. Because treatment always has side effects to some extent, awareness of possible late effects after treatment remains important for patients and treating physicians.

Incidence of hypothyroidism after radiotherapy for nasopharyngeal carcinoma

OBJECTIVES

The thyroid gland is frequently affected by radiotherapy applied for the treatment of head and neck tumors. Hypothyroidism is observed as a late side effect of radiotherapy, especially seen in the patients who have surgery in the treatment procedure.

METHODS

We evaluated the radiation-induced hypothyroidism for a selected type of head and neck cancer- nasopharyngeal cancer (NPC)-which does not include surgery involving the thyroid gland in the treatment.

RESULTS

We observed 12 patients (14%) who developed hypothyroidism, two of which were subclinical hypothyroidism. The patients with hypothyroidism were statistically significantly younger than the euthyroid patients, but there were no statistically significant differences among the two groups in disease stages, radiotherapy neck doses, and gender.

CONCLUSIONS

We recommend life-long TSH screening after RT to the neck owing to the incidence of RTinduced hypothyroidism and the importance of early thyroid hormone replacement therapy in patients becoming hypothyroid for maintaining optimal quality of life.

White race as a risk factor for hypothyroidism after treatment for pediatric Hodgkin's lymphoma

PURPOSE

Hypothyroidism frequently occurs after treatment for pediatric Hodgkin's lymphoma, but race has not been investigated as a risk factor for this delayed toxicity. The aim of this study was to determine whether race is an independent risk factor for hypothyroidism in survivors of pediatric Hodgkin's lymphoma.

PATIENTS AND METHODS

To identify differences between black and white patients in the development of hypothyroidism after treatment for Hodgkin's lymphoma, we conducted a retrospective study of consecutively treated pediatric patients with newly diagnosed Hodgkin's lymphoma treated at St Jude Children's Research Hospital (Memphis, TN) from January 1980 through December 2002. Clinical or biochemical hypothyroidism was defined by an above normal thyroxine-stimulating hormone concentration or by the need for thyroid hormone replacement therapy.

RESULTS

The 461 patients (388 white patients, 73 black patients) where followed for a median of 11.3 years (range, 1.8 to 24.9 years). Hypothyroidism developed in 196 (43%) of 461 patients after a median of 2.9 years (range, 0.7 to 11.3 years) after diagnosis of Hodgkin's lymphoma. Hypothyroidism developed in 47% of white patients but in only 21% of black patients (hazard ratio = 2.7; 95% CI, 1.6 to 4.6). After adjusting for other risk factors for hypothyroidism (thyroid radiation dose, sex, and nodular sclerosis histology), the risk of hypothyroidism in white patients was 2.5 times (95% CI, 1.5 to 4.3 times) the risk in black patients (P < .001).

CONCLUSION

White patients have a higher risk of hypothyroidism after neck irradiation for pediatric Hodgkin's lymphoma than black patients.

Self‐reported health and use of health care services in long‐term cancer survivors

Owing to an increasing number of long-term cancer survivors, the use of health care services and somatic health problems were compared between cancer survivors and a noncancer population. Data from the Nord-Trondelag Health Survey 2 (HUNT 2, 1995-1997) was merged with the Cancer Registry of Norway. Six cancer subgroups were constructed with diagnosis 5 years prior HUNT 2: testicular cancer (n= 59), colorectal cancer (n= 175), prostate cancer (n= 87), breast cancer (n= 258), gynaecological cancer (n= 153) and lymphoma/leukaemia (n= 83). For each cancer survivor 3 matched noncancer controls were selected from the HUNT 2 survey. The prevalence of common health problems, use of health care services and unfavourably life style parameters were compared between the 2 groups. Cancer survivors used health care services and received social welfare benefits more often than the controls. There was an increased risk of perceiving poor health after a history of cancer. Common health problems and/or unfavourable life style parameters could not explain poor health or the increased use of health care services among cancer survivors. Further studies are needed to investigate the reasons for increased use of health care services and perceived poor health in cancer survivors.

Thyroid function after bone marrow transplantation: possible association between immune-mediated thyrotoxicosis and hypothyroidism

BACKGROUND

Thyroid dysfunction after bone marrow transplantation (BMT) has been investigated in many studies, and most posttransplant thyroid disorders are now recognized as a late complication of transplantation. However, these studies mainly focused on late thyroid function after BMT, and we have little information on early changes of thyroid function after BMT.

METHODS

We prospectively investigated thyroid function in 57 patients receiving BMT. Serum thyroid-stimulating hormone, free triiodothyronine, and free thyroxine levels were determined at least monthly in the first 3 months, once between 3 and 12 months and once in the second year after BMT.

RESULTS

During the first 6 months after BMT, 24 and 7 patients were diagnosed as having euthyroid sick syndrome (ETS) and thyrotoxicosis, respectively. Of the 52 patients alive 1 year after transplantation, 9 patients were still diagnosed as having ETS, and 8 patients developed hypothyroidism. Patients with thyrotoxicosis showed similar characteristics, and the high incidence of thyrotoxicosis after BMT is a novel finding. The median for the onset of thyrotoxicosis was day 111 after transplantation. Thyrotoxicosis was transient in all of the patients, but in seven patients hypothyroidism followed, the median onset at 12 months after BMT. Serum thyroglobulin levels were elevated in five patients, and antibodies autoreactive to the thyroid gland were detected in seven patients.

CONCLUSIONS

Thyrotoxicosis may be a distinct clinical entity of thyroid dysfunction after BMT and may serve to predict the development of hypothyroidism. Immune-mediated thyroid injury may contribute to the development of posttransplant hypothyroidism.