Hypothyroidism after radiotherapy for patients with head and neck cancer

Hypothyroidism in Head and Neck Squamous Cell Carcinoma Patients Receiving Radiotherapy With or Without Immune Checkpoint Inhibitors

OBJECTIVES/HYPOTHESIS

Hypothyroidism is a relatively common complication of head and neck squamous cell carcinoma (HNSCC) treatment. The objective of this study was to determine whether the addition of programmed death ligand-1 (PD-1) or programmed death ligand-1 (PD-L1) inhibition (anti-PD-1/PD-L1 therapy) to standard treatment increases the risk of hypothyroidism in HNSCC.

STUDY DESIGN

Retrospective Cohort.

METHODS

This is a retrospective, single institutional cohort study. Patients who received radiotherapy (RT) for HNSCC were identified in the electronic medical record. Patient factors collected include age, sex, body mass index (BMI), smoking status, alcohol use, Charlson comorbidity index, and HNSCC treatment records. The rate of hypothyroidism for patients with HNSCC receiving RT (+/- chemotherapy and surgery) (RT group, n = 101) was compared to that of HNSCC patients receiving RT (+/- chemotherapy and surgery) + anti-PD-1/PD-L1 therapy, either concurrently or after RT (RT + anti-PD-1/PD-L1 group, n = 38).

RESULTS

There was no significant difference in the rate of clinical or subclinical hypothyroidism between the two groups. Multinomial logistic regression found no significant difference in hypothyroidism based on age, sex, or BMI.

CONCLUSIONS

The addition of anti-PD-1/PD-L1 therapy to standard HNSCC treatment does not significantly increase the risk of developing hypothyroidism.

LEVEL OF EVIDENCE

3 Laryngoscope, 131:E2413-E2419, 2021.

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.

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.

Radiotherapeutic factors affecting the incidence of developing hypothyroidism after radiotherapy for head and neck squamous cell cancer

PURPOSE

The purpose of this study is to determine radiotherapy (RT) dose-volumetric threshold of radiation-induced hypothyroidism (HT) in head and neck squamous cell carcinoma (HNSCC) patients.

PATIENTS AND METHODS

The diagnosis of HT in 78 HNSCC patients treated with RT was based on a thyroid stimulating hormone (TSH) level greater than the maximum value of laboratory range. In all patients, dose-volumetric parameters were analyzed according to their relation to development of HT, and thyroid volumes spared from doses ≥10, 20, 30, 40 and 50 Gy (V10, V20, V30, V40 and V50) were analyzed from the dose volume histograms (DVHs).

RESULTS

Median follow-up duration was 31 months. At the end of study, 33 patients (42.3%) developed HT and the cumulative incidence of HT was 24.6%, 36.5% and 42.3% at one, two and three years, respectively. V30 of 42.1% (P = 0.005) was defined as dose-volumetric threshold of radiation-induced HT in HNSCC patients. Our analysis showed that V30 separates patients into low- and high-risk groups; the incidence of radiation-induced HT in the group with V30 < 42.1% and V30 ≥ 42.1% was 29.4% and 71.4%, respectively (P = 0.002).

CONCLUSIONS

The V30 may predict risk of developing HT after RT for HNSCC patients. V30 of 42.1%, defined as dose-volumetric threshold of radiation-induced HT, can be useful in treatment planning of HNSCC patients.

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.

Calculation of Thyroid Dose with Planner System and Evaluation of Thyroid Function after Radiotherapy for Patients with Breast Cancer

BACKGROUND

Much research has widely been conducted into thyroid hormones levels following radiotherapy for breast cancer. Consequently, in this study, we evaluated to relate the rate of thyroid hormones levels with the dose distribution among breast cancer patients.

MATERIAL AND METHODS

Thirty patients were treated with 4-field breast cancer radiotherapy. The dose volume histograms, the volume percentage of the thyroid absorbing respectively 20, 30, 40 and 50 Gy were then estimated (V20, V30, V40 and V50) together with the individual average thyroid dose over the whole gland derived from their computed tomography-based treatment plans. Then, in serum samples triiodothyronine [T3], thyroxine [T4], thyroid-stimulating hormone [TSH] of the patients were measured before and after radiotherapy.

RESULTS

There were no significant differences in thyroid hormones levels before and after radiotherapy for patients with breast cancer (P value >.05).

CONCLUSION

On the balance, we understood that thyroid stimulating hormones levels did not change before and after cancer breast radiotherapy.

Correlative study of dose to thyroid and incidence of subsequent dysfunction after head and neck radiation

BACKGROUND

Thyroid dysfunction is common after radiotherapy (RT) for patients with head and neck cancers. We attempted to discover RT dose parameters that correspond with RT-induced thyroid dysfunction.

METHODS

Records of 102 patients who received RT from 2008 to 2010 were reviewed with respect to thyroid function. Abnormalities were grouped in 2 ways: (1) none, transient, or permanent; and (2) overt or subclinical.

RESULTS

At median follow-up of 33.5 months, incidence of any thyroid abnormality was 39.2% (women vs men - 50% vs 35%). Permanent dysfunction was seen in 24.5% with higher incidence in women versus men (42.9% vs 17.6%; p = .0081). Permanent abnormalities most strongly correlated with D_50% (p = .0275). V_50Gy also correlated with thyroid dysfunction post-RT (p = .0316). Concurrent chemotherapy increased permanent dysfunction (p = .0008).

CONCLUSION

Achieving D_50% <50 Gy, V₅₀ <50%, and mean dose <54.58 Gy during RT planning may decrease the incidence; whereas female sex and concurrent chemotherapy seem to increase the risk of RT-induced hypothyroidism. © 2016 Wiley Periodicals, Inc. Head Neck 39: 548-554, 2017.

Calculation of Thyroid Dose with Planner System and Evaluation of Thyroid Function after Radiotherapy for Patients with Breast Cancer

BACKGROUND

Much research has widely been conducted into thyroid hormones levels following radiotherapy for breast cancer. Consequently, in this study, we evaluated to relate the rate of thyroid hormones levels with the dose distribution among breast cancer patients.

MATERIAL AND METHODS

Thirty patients were treated with 4-field breast cancer radiotherapy. The dose volume histograms, the volume percentage of the thyroid absorbing respectively 20, 30, 40 and 50 Gy were then estimated (V20, V30, V40 and V50) together with the individual average thyroid dose over the whole gland derived from their computed tomography-based treatment plans. Then, in serum samples triiodothyronine [T3], thyroxine [T4], thyroid-stimulating hormone [TSH] of the patients were measured before and after radiotherapy.

RESULTS

There were no significant differences in thyroid hormones levels before and after radiotherapy for patients with breast cancer (P value >.05).

CONCLUSION

On the balance, we understood that thyroid stimulating hormones levels did not change before and after cancer breast radiotherapy.

Hypothyroidism in patients treated with radiotherapy for head and neck carcinoma: standardised long-term follow-up study

OBJECTIVE

Hypothyroidism is a common complication when radiotherapy is part of the treatment for head and neck tumours. This study aimed to show the incidence of hypothyroidism and possible risk factors in these patients.

METHODS

Factors related to the population, tumour, treatment and occurrence of hypothyroidism were analysed in 241 patients diagnosed with head and neck carcinoma.

RESULTS

Approximately 53 per cent of patients were diagnosed with radiation-induced hypothyroidism. Its occurrence was related to: tumour location, laryngeal surgery type, neck dissection type, post-operative complications, cervical radiotherapy and radiotherapy unit type (linear particle accelerator or telecobalt therapy technology).

CONCLUSION

Control of thyroid function should be standardised for several years after treatment, particularly in patients with risk factors, such as those treated with telecobalt therapy, those with post-operative complications and for whom the thyroid parenchyma is included in the irradiated area (laryngeal or pharyngeal location and bilateral cervical radiation).

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

The purpose of the present study was to determine the risk factors for developing thyroid disorders based on a dose-volume histograms (DVHs) analysis. Data from a total of 116 consecutive patients undergoing 3D conformal radiation therapy for head and neck cancers was retrospectively evaluated. Radiation therapy was performed between April 2007 and December 2010. There were 108 males and 8 females included in the study. The median follow-up term was 24 months (range, 1-62 months). The thyroid function was evaluated by measuring thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels. The mean thyroid dose, and the volume of thyroid gland spared from doses ≥10, 20, 30 and 40 Gy (VS10, VS20, VS30 and VS40) were calculated for all patients. The thyroid dose and volume were calculated by the radiotherapy planning system (RTPS). The cumulative incidences of hypothyroidism were 21.1% and 36.4% at one year and two years, respectively, after the end of radiation therapy. In the DVH analyses, the patients who received a mean thyroid dose <30 Gy had a significantly lower incidence of hypothyroidism. The univariate analyses showed that the VS10, VS20, VS30 and VS40 were associated with the risk of hypothyroidism. Hypothyroidism was a relatively common type of late radiation-induced toxicity. A mean thyroid dose of 30 Gy may be a useful threshold for predicting the development of hypothyroidism after radiation therapy for head and neck cancers.

Longitudinal study on the correlations of thyroid antibody and thyroid hormone levels after radiotherapy in patients with nasopharyngeal carcinoma with radiation-induced hypothyroidism

BACKGROUND

The purpose of this study was to evaluate the correlations of thyroid antibody and thyroid hormone in postradiotherapy (post-RT) patients with nasopharyngeal carcinoma (NPC).

METHODS

Serum thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), thyroperoxidase antibody (anti-TPO), and thyroglobulin antibody (anti-TG) levels of 55 patients with NPC were taken before RT and at 3, 6, 12, and 18 months after RT. Patients with hypothyroidism at 18 months after RT and those with normal thyroid function were categorized into the hypo and normal groups, respectively. The thyroid antibody levels were compared between the 2 groups, and the correlations of thyroid antibody and thyroid hormone were evaluated for the hypo group.

RESULTS

The anti-TPO and anti-TG of the hypo group were higher than the normal group. In the hypo group, there was a positive correlation (r = 0.51) between TSH and anti-TG and a negative correlation between fT4 and anti-TPO (r = -0.55).

CONCLUSION

There were correlations of the thyroid antibody and thyroid hormone levels in patients with radiation-induced hypothyroidism.

Acquired disorders of the thyroid following treatment for head and neck cancer

The multimodality management of head and neck cancer routinely utilizes radiation therapy in treatment. The hypothalamus, pituitary and thyroid gland may be included within treatment fields. The incidence of human papilloma virus-associated oropharyngeal carcinoma has seen a dramatic increase over the last 3 decades. Current guidelines for the long-term aftercare assessment advocate only for thyroid-stimulating hormone levels every 6-12 months after baseline posttreatment imaging. With a growing population of younger patients with a favorable prognosis exposed to therapeutic radiation therapy, it is anticipated that incidence of thyroid-associated complications, such as hypothyroidism and thyroid cancer, could increase significantly over time. Constructing a strategy for the long-term reassessment of these patients beyond existing guidelines may be necessary.

Estimation of absorbed dose to thyroid in patients treated with radiotherapy for various cancers

This study is aimed at the evaluation of the absorbed dose to the thyroid gland from scattered/primary radiations in patients who have undergone radiotherapy. In this study, the skin entrance dose (SED) on the anterior neck at the level of the thyroid gland was measured using thermoluminescent dosimeters for 57 patients during radiotherapy with (60)Co teletherapy unit. Phantom dosimetry was also performed to find the correlation between the SED and the dose at the depth of the thyroid. SED of patients treated for breast cancer was 6.77±3.49 Gy and that of those with Hodgkin's disease and Ca. lung irradiation were 21.29±13.52 Gy and 28.80±14.94 Gy, respectively. SED at the level of the thyroid gland was found to be highest for patients whose thyroid gland was within the radiation field, while lowest for patients with skull irradiation. Thyroid gland is recommended to be shielded or excluded from the field whenever possible.

Dose distribution in the thyroid gland following radiation therapy of breast cancer--a retrospective study

Purpose

To relate the development of post-treatment hypothyroidism with the dose distribution within the thyroid gland in breast cancer (BC) patients treated with loco-regional radiotherapy (RT).

Methods and materials

In two groups of BC patients postoperatively irradiated by computer tomography (CT)-based RT, the individual dose distributions in the thyroid gland were compared with each other; Cases developed post-treatment hypothyroidism after multimodal treatment including 4-field RT technique. Matched patients in Controls remained free for hypothyroidism. Based on each patient's dose volume histogram (DVH) the volume percentages of the thyroid absorbing respectively 20, 30, 40 and 50 Gy were then estimated (V20, V30, V40 and V50) together with the individual mean thyroid dose over the whole gland (MeanTotGy). The mean and median thyroid dose for the included patients was about 30 Gy, subsequently the total volume of the thyroid gland (VolTotGy) and the absolute volumes (cm³) receiving respectively < 30 Gy and ≥ 30 Gy were calculated (Vol < 30 and Vol ≥ 30) and analyzed.

Results

No statistically significant inter-group differences were found between V20, V30, V40 and V50Gy or the median of MeanTotGy. The median VolTotGy in Controls was 2.3 times above VolTotGy in Cases (ρ = 0.003), with large inter-individual variations in both groups. The volume of the thyroid gland receiving < 30 Gy in Controls was almost 2.5 times greater than the comparable figure in Cases.

Conclusions

We concluded that in patients with small thyroid glands after loco-radiotherapy of BC, the risk of post-treatment hypothyroidism depends on the volume of the thyroid gland.

The incidence of thyroid dysfunction following radiotherapy for early stage carcinoma of the larynx

External beam radiotherapy is currently the commonest form of treatment for early laryngeal cancer (T1/2) and thyroid dysfunction is a well recognised complication of this treatment. Overt hypothyroidism is a specific clinical disorder which in most patients will be recognized and treated. The problems associated with subclinical hypothyroidism (elevated TSH with normal T4), however, are only now being recognized and their management is to some extent still controversial. The aims of our study are to determine the incidence of clinical and subclinical hypothyroidism in those who have been treated solely with curative radiotherapy for early laryngeal cancer. We performed a retrospective observational study encompassing all patients who underwent curative radiotherapy for T1/T2 laryngeal cancer between 1998 and 2002. 33 patients were identified (mean 66.85 years, range 48-93). 19 patients had T1 lesions (58%), 14 had T2 lesions (42%) and 27 were N0 (82%). 23 patients were euthyroid post treatment (70%), 2 became overtly hypothyroid (6%) and 8 developed subclinical hypothyroidism (24%). There was no association between tumour stage (p = 0.97), nodal stage (p = 0.46) and thyroid status, however, there was an association between increasing age and deteriorating thyroid function (p = 0.01). Our study showed that of patients with early laryngeal cancers treated solely with curative radiotherapy 24% developed subclinical hypothyroidism and 6% were overtly hypothyroid (Elevated TSH and reduced T4). We feel patients should receive regular thyroid function testing following completion of treatment and should be adequately counselled on the risk of thyroid dysfunction following radiotherapy at pre-treatment visits.

A longitudinal study on the radiation-induced thyroid gland changes after external beam radiotherapy of nasopharyngeal carcinoma

BACKGROUND

Radiation-induced thyroid disorders have been reported in radiotherapy of head and neck cancers. This study evaluated the radiation-induced damages to thyroid gland in patients with nasopharyngeal carcinoma (NPC).

METHODS

Forty-five patients with NPC treated by radiotherapy underwent baseline thyroid hormones (free triiodothyronine, free thyroxine [fT4], and thyrotropin [TSH]) examination and CT scan before radiotherapy. The volume of the thyroid gland was calculated by delineating the structure in the corresponding CT slices using the radiotherapy treatment planning system. The thyroid doses were estimated using the treatment planning system. Subsequent CT scans were conducted at 6, 12, and 18 months after radiotherapy, whereas the hormone levels were assessed at 3, 6, 12, and 18 months after radiotherapy. Trend lines of the volume and hormone level changes against time were plotted. The relationship between the dose and the change of thyroid volume and hormone levels were evaluated using the Pearson correlation test.

RESULTS

An average of 20% thyroid volume reduction in the first 6 months and a further 8% shrinkage at 12 months after radiotherapy were observed. The volume reduction was dependent on the mean thyroid doses at 6, 12, and 18 months after radiotherapy (r = -0.399, -0.472, and -0.417, respectively). Serum free triiodothyronine and fT4 levels showed mild changes of <2.5% at 6 months, started to drop by 8.8% and 11.3%, respectively, at 12 months, and became stable at 18 months. The mean serum TSH level increased mildly at 6 months after radiotherapy and more steeply after 18 months. At 18 months after radiotherapy, 12 patients had primary hypothyroidism with an elevated serum TSH, in which 4 of them also presented with low serum fT4. There was a significant difference (p = 0.014) in the mean thyroid doses between patients with hypothyroidism and normal thyroid function.

CONCLUSIONS

Radiotherapy for patients with NPC caused radiation-induced changes of the thyroid gland. The shrinkage of the gland was greatest in the first 6 months after radiotherapy, whereas the serum fT4 and TSH levels changed at 12 months. Radiation-induced changes were dependent on the mean dose to the gland. Therefore, measures to reduce the thyroid dose in radiotherapy should be considered.

Screening for thyroid disease: defining high-risk populations

The pros and cons of population screening for thyroid disease have been hotly debated over the past several decades. This article addresses the issue from the point of view of the potential benefit of screening, that is, disease detection. Earlier diagnoses of hypothyroidism, hyperthyroidism, thyroid nodules, thyroid cancer and so on, with implementation of the indicated diagnostic and therapeutic interventions, avoid the adverse consequences of unrecognized and untreated progressive disease. Arguments against screening and case-finding often focus on cost considerations. To achieve the greatest yield at the lowest cost, our emphasis is on vulnerable populations with associated risk factors, and special situations such as pregnancy.

Hypothyroidism in postradiation head and neck cancer patients: incidence, complications, and management

PURPOSE OF REVIEW

To describe the incidence, risk factors, prevention, and management of hypothyroidism among patients treated with radiation and other modalities for head and neck cancers.

RECENT FINDINGS

Hypothyroidism may occur in up to 48% of patients treated for head and neck malignancies. It has been observed after radiation, surgery, and combined-modality therapies. The onset of hypothyroidism may be as early as 4 weeks and as late as 5 or 10 years after completion of therapy. It has been associated with poor wound healing, bleeding disorders, and a number of other potential complications germane to the practice of head and neck surgery. There is some evidence to suggest a protective role of hypothyroidism with respect to disease control survival in head and neck and other cancers.

SUMMARY

Hypothyroidism is common after treatment of head and neck cancers. Thyroid function studies should be obtained prior to and at regular intervals after treatment. Prompt recognition and intervention may prevent or reverse adverse physiological outcomes. Further studies are necessary to evaluate the role of permissive hypothyroidism in the context of treated head and neck malignancies.

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.

Radiotherapeutic management of laryngeal carcinoma

Authors discuss laryngeal lesions, metastases, and relevant anatomy. Outcome of surgical and radiotherapy in terms of voice preservation is discussed. Radiation techniques and outcomes for laryngeal cancer are presented along with discussion of interdisciplinary treatment. Authors review studies and quality of life outcomes of surviving laryngeal cancer patients.

The need for patients' endocrine function vigilance following treatment of head and neck cancer

PURPOSE OF REVIEW

The aim of this article is to examine the need for screening of endocrine dysfunction following treatment of head and neck cancer.

RECENT FINDINGS

The incidence of occult hypothyroidism following treatment of head and neck cancer is high. Patients who develop hypothyroidism after treatment may have an increased survival compared with patients who did not become hypothyroid. Because of the growing body of evidence that supports a permissive role for thyroid hormone in the growth of certain solid tumours thyroid hormone replacement therapy may not be indicated in patients with subclinical hypothyroidism and prior or current cancer. Although the incidence of hypoparathyroidism after treatment for head and neck cancer is low, testing of serum calcium is easily performed during thyroid function evaluation. The incidence of hypopituitarism after irradiation of the nasopharynx or skull base is very high warranting regular evaluation of endocrine functions.

SUMMARY

Owing to the high incidence of endocrine dysfunction, all head and neck cancer patients who undergo treatment of the lower neck, nasopharynx or base of skull need regular endocrine evaluation during long-term follow-up to determine the need to start hormone replacement therapy and maintain optimal quality of life.