Evaluation of thyroid gland as an organ at risk after breast cancer radiotherapy: a systematic review and meta-analysis

Effect of comorbidity and multimorbidity on adherence to follow-up recommendations among long-term breast cancer survivors

OBJECTIVES

To study the impact of comorbidities, multimorbidity, and multimorbidity clusters on adherence to recommended follow-up guidelines among long-term breast cancer survivors.

STUDY DESIGN

Retrospective cohort study based on 2078 women diagnosed with breast cancer from 2000 to 2006 and followed up from 2012 to 2016.

MAIN OUTCOME MEASURES

Adherence to breast cancer follow-up recommendations (annual medical visit and imaging) was determined. Comorbidities were classified as acute/chronic. Multimorbidity was defined as the presence of two or more chronic comorbidities aside from breast cancer. Five multimorbidity clusters were considered. Multivariate logistic regression models were fitted to determine the relationship between adherence to recommendations and the presence of comorbidities and multimorbidity, considering both sociodemographic and clinical characteristics.

RESULTS

Overall adherence to recommendations was 79.5 %. Adherence was lower among long-term breast cancer survivors with no comorbidities (75.8 %). Among multimorbidity clusters, adherence was highest in the anxiety and fractures cluster (84.3 %) and was lowest in the musculoskeletal and cardiovascular cluster (76.4 %). In adjusted multivariate models, multimorbidity was associated with higher levels of adherence (OR = 1.52 95 %CI 1.16-1.99), and adherence was highest in the metabolic and degenerative cluster (OR = 2.2 95 %CI 1.4-3.5).

CONCLUSION

Adherence to follow-up recommendations was higher among long-term breast cancer survivors with multimorbidity than among those without. Adherence also differed by multimorbidity cluster. These results suggest suboptimal adherence to the current follow-up recommendations in certain groups, suggesting the need to adapt clinical practice guidelines to reflect patients' comorbidities and different characteristics.

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

Purpose

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

Materials and methods

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

Results

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

Conclusions

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

Incidence and risk factors of hypothyroidism after treatment for early breast cancer: a population-based cohort study

PURPOSE

An increased incidence of hypothyroidism among breast cancer survivors has been observed in earlier studies. The impact of the postoperative treatment modalities and their potential interplay on hypothyroidism development needs to be studied.

METHODS

We conducted a population- and registry-based study using the Breast Cancer Data Base Sweden (BCBaSe) including females diagnosed with breast cancer between 2006 and 2012. In total, 21,268 female patients diagnosed with early breast cancer between 2006 and 2012, with no previous prescription of thyroid hormones and no malignant diagnosis during the last ten years before breast cancer diagnosis, were included in the final analysis.

RESULTS

During the follow-up (median follow-up time 7.9 years), 1212 patients (5.7%) developed hypothyroidism at a median time of 3.45 years from the index date. No association of the systemic oncological treatment in terms of either chemotherapy or endocrine therapy and hypothyroidism development could be identified. A higher risk (HR 1.68;95% CI 1.42-1.99) of hypothyroidism identified among patients treated with radiation treatment of the regional lymph nodes whereas no increased risk in patients treated only with radiation therapy to the breast/chest wall was found (HR 1.01; 95% CI 0.86-1.19). The risk of hypothyroidism in the cohort treated with radiotherapy of the regional lymph nodes was present irrespective of the use of adjuvant chemotherapy treatment.

CONCLUSIONS

Based on the results of our study, the implementation of hypothyroidism surveillance among the breast cancer survivors treated with radiotherapy of the regional lymph nodes can be considered as reasonable in the follow-up program.

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

PURPOSE

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

MATERIAL AND METHODS

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

RESULTS

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

CONCLUSION

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

Breast cancer, breast cancer-directed radiation therapy and risk of hypothyroidism: A systematic review and meta-analysis

OBJECTIVE

Breast cancer and breast cancer-directed radiation therapy (RT) may increase the risk of late effects, such as hypothyroidism. We conducted a systematic review and meta-analysis to investigate the association between breast cancer, RT, and risk of hypothyroidism in breast cancer survivors.

METHODS

Through February 2022, we searched PubMed, EMBASE, and references of relevant articles, to identify papers on breast cancer and breast cancer-directed RT and subsequent risk of hypothyroidism. Articles were screened by title and abstract and reviewed for eligibility. We used a pre-formed data extraction sheet and identified key design elements that could potentially introduce bias. The main outcome was the confounder-adjusted relative risk (RR) of hypothyroidism in breast cancer survivors versus women without breast cancer, and in breast cancer survivors according to the receipt of RT to the supraclavicular lymph nodes. We used a random-effects model to calculate pooled RRs and associated 95% confidence intervals (95% CI).

RESULTS

From 951 papers screened by title and abstract, 34 full-text papers were reviewed for eligibility. We included 20 studies published between 1985 and 2021-19 were cohort studies. Compared with women without breast cancer, the pooled RR of hypothyroidism in breast cancer survivors was 1.48 (95% CI: 1.17, 1.87), with highest risk associated with RT to the supraclavicular region (RR = 1.69, 95% CI: 1.16, 2.46). The most important limitations of the studies were small sample size yielding estimates with low precision, and lack of data on potential confounders.

CONCLUSION

Breast cancer and radiation therapy to the supraclavicular lymph nodes is associated with an increased risk of hypothyroidism.

Radiation-Induced Hypothyroidism in Patients With Breast Cancer After Hypofractionated Radiation Therapy: A Prospective Cohort Study

PURPOSE

Our objective was to assess the incidence and risk factors of radiation-induced hypothyroidism (RHT) after adjuvant hypofractionated radiation therapy (RT) in patients with breast cancer.

METHODS AND MATERIALS

Eligible patients with breast cancer who were treated with hypofractionated RT were prospectively evaluated. Thyroid function tests were performed before and at regular times after RT. RHT was defined as twice elevated serum thyroid-stimulating hormone (TSH) with decreased or normal free thyroxin after RT. The patient, tumor, and treatment factors were evaluated for possible associations with the risk of RHT.

RESULTS

Five hundred patients were analyzed. All patients underwent chest wall/breast with or without regional nodal irradiation. Among them, 369 (73.8%) patients received supraclavicular nodal radiation (SCRT). Eighty-two (16.4%) patients had elevated TSH before RT. At a median follow-up of 21.9 months, 131 (26.2%) patients developed RHT, and 59 (11.8%) patients received thyroid hormone-replacement therapy. Patients with SCRT had a significantly increased 2-year cumulative incidence of RHT compared with patients without SCRT (31.5% and 11.4%, P<.001). The peak incidence of RHT occurred around 6 to 12 months after RT. Multivariate analysis revealed that elevated baseline TSH and increased thyroid mean dose (Dmean) were independent risk factors for developing RHT. After adjusted for baseline TSH, there was a nonlinear relationship between thyroid Dmean and the risk of RHT. Dmean >21 Gy was the threshold value for predicting RHT (hazard ratio, 2.2; P<.001).

CONCLUSIONS

The incidence of RHT was high in patients with breast cancer. Thyroid function test should be started no later than 6 months after RT. We recommend that the Dmean of the thyroid should be kept lower than 21 Gy for hypofractionated RT.

Thyroid volume changes following adjuvant radiation therapy for breast cancer

Background and purpose

Incidental thyroid gland irradiation frequently occurs in breast cancer patients who receive regional nodal irradiation (RNI) to the supraclavicular (SCV) region. Recent studies suggest hypothyroidism (HT) is a complication of radiation therapy (RT) that includes SCV fields. We retrospectively analyzed patients who received RNI to evaluate thyroid gland evolution following RT as well as its association with the development of HT.

Materials and methods

61 breast cancer patients received SCV-directed RT between 2007 and 2019 and met inclusion criteria. Thyroid glands were retrospectively contoured on CT simulation and follow-up images. Individual dose-volume histograms were analyzed to determine thyroid volume within and outside specific isodose lines. Relative thyroid volume changes based on different radiation doses were estimated by fusing post-RT scans with CT simulation. Logistic regression was performed to assess thyroid volume changes as a factor in the development of HT.

Results

Median pre-treatment thyroid volume was 11.8 cc (range: 6.3-74.1 cc) with a median of 42.2 % within the 20 Gy and 23.2 % within the 40 Gy isodose lines. A significant decrease in thyroid volume was noted by 1-year post-treatment (p < 0.0001) and thereafter. By 4 years post-treatment, average thyroid volume was decreased by 29.7 % (range: 2.3-64.4 %). Thyroid volume receiving 40 Gy or higher demonstrated a greater decrease compared to those receiving lower irradiation dosage. HT occurred in 17 patients (27.9 %). Patients who developed HT displayed a larger decrease in the thyroid volume receiving between 20 and 40 Gy at 12 months (p = 0.033).

Conclusion

Our study demonstrates for the first time that a reduction in thyroid volume may be seen as early as 6 months after SCV-directed RT for breast cancer, which correlates with development of clinical and subclinical HT. Furthermore, a dose-dependent correlation exists between thyroid subvolume reduction and SCV-directed RT in breast cancer patients. As feasible, efforts should be made to reduce the dose to the thyroid in patients who undergo RNI for breast cancer.

Links between Breast and Thyroid Cancer: Hormones, Genetic Susceptibility and Medical Interventions

Breast and thyroid glands are two common sites of female malignancies. Since the late 19th century, physicians have found that the cancers in either thyroid or mammary gland might increase the risk of second primary cancers in the other site. From then on, many observational clinical studies have confirmed the hypothesis and more than one theory has been developed to explain the phenomenon. Since the two glands both have secretory functions and are regulated by the hypothalamic-pituitary axis, they may share some common oncogenic molecular pathways. However, other risks factors, including medical interventions and hormones, are also observed to play a role. This article aims to provide a comprehensive review of the associations between the two cancers. The putative mechanisms, such as hormone alteration, autoimmune attack, genetic predisposition and other life-related factors are reviewed and discussed. Medical interventions, such as chemotherapy and radiotherapy, can also increase the risk of second primary cancers. This review will provide novel insights into the research designs, clinical managements and treatments of thyroid and breast cancer patients.

Cancer-specific mortality in breast cancer patients with hypothyroidism: a UK population-based study

PURPOSE

Epidemiological studies have indicated a higher prevalence of hypothyroidism in breast cancer patients, possibly related to shared risk factors and breast cancer treatments. However, few studies have evaluated how hypothyroidism impacts survival outcomes in breast cancer patients. We aimed to determine the association between hypothyroidism and breast cancer-specific and all-cause mortality.

METHODS

We conducted a population-based study using the Scottish Cancer Registry to identify women diagnosed with breast cancer between 2010 and 2017. A matched comparison cohort of breast cancer-free women was also identified. Using hospital diagnoses and dispensed prescriptions for levothyroxine, we identified hypothyroidism diagnosed before and after breast cancer diagnosis and determined associations with breast cancer-specific and all-cause mortality. Cox proportional hazards regression was used to calculate hazard ratios (HR) and 95% confidence intervals (CI) adjusted for potential confounders.

RESULTS

A total of 33,500 breast cancer patients were identified, of which 3,802 had hypothyroidism before breast cancer diagnosis and 565 patients went on to develop hypothyroidism after. Breast cancer patients had higher rates of hypothyroidism compared with cancer-free controls (HR 1.14, 95% CI 1.01-1.30). Among breast cancer patients, we found no association between hypothyroidism (diagnosed before or after) and cancer-specific mortality (before: HR 0.99, 95% CI 0.88-1.12, after: HR 0.97, 95% CI 0.63-1.49). Similar associations were seen for all-cause mortality.

CONCLUSION

In a large contemporary breast cancer cohort, there was little evidence that hypothyroidism, either at diagnosis or diagnosed after breast cancer, was associated with cancer-specific or all-cause mortality.

The Combined Clinical Diagnosis of TNF-α, TSH, and p185 Protein in Breast Cancer

Objective

To study the concentrations of tumor necrosis factor (TNF-α), thyroid-stimulating hormone (TSH), and c-erbB-2 oncogene protein product P185 in different pathological stages of breast cancer and to analyze their combined clinical diagnosis of breast cancer significance.

Methods

67 breast cancer patients who were treated in our hospital from January 2018 to September 2020 were set as the breast cancer group and were divided into stages I, II, III, and IV according to clinicopathology. In addition, 55 patients with benign breasts who were admitted to the hospital at the same time were selected as the benign breast group, and 60 healthy people in our hospital during the same period were selected as the healthy group. The differences between serum TNF-α, TSH, and p185 protein positive rate in 3 groups and the levels of TNF-α and TSH and p185 protein positive rate in patients with different pathological characteristics were compared and analyzed, and the differences between the combined detection and the single detection were analyzed.

Results

Compared with the benign breast group and the healthy group, the serum levels of TNF-α (44.61 ± 12.54 versus 29.75 ± 10.19 versus 56.87 ± 15.36 versus 102.37 ± 15.36), TSH (0.98 ± 0.13 versus 0.94 ± 0.17 versus 1.17 ± 0.24 versus 1.22 ± 0.15) and p185 protein positive rate were higher in the I-II and III-IV groups, and the difference was statistically significant (P < 0.05). TNF-α detection sensitivity was 44.74%, specificity was 62.06%, which was higher than p185 sensitivity of 31.01%, specificity of 49.78%, higher than TSH sensitivity of 27.51%, specificity of 39.77%. At the same time, the sensitivity and specificity of combined detection of TNF-α, TSH, and p185 protein were 67.35% and 70.41%, which were significantly higher than the sensitivity and specificity of single detection, and the difference was statistically significant (P < 0.05).

Conclusion

TNF-α, TSH, and p185 protein are expected to be used as auxiliary basis for diagnosis in the future. But in general, the serum indexes in this study had low sensitivity and specificity for the diagnosis of breast cancer, which limited their diagnostic function in clinical use.

The role of radiogenomics in the diagnosis of breast cancer: a systematic review

Background

One of the most common cancers diagnosed worldwide is breast cancer (BC), which is the leading cause of cancer death among women. The radiogenomics method is more accurate for managing and inhibiting this disease, which takes individual diagnosis on genes, environments, and lifestyles of each person. The present study aims to highlight the current state-of-the-art, the current role and limitations, and future directions of radiogenomics in breast cancer.

Method

This systematic review article was searched from databases such as Embase, PubMed, Web of Science, Google Scholar, Scopus, and Cochrane Library without any date or language limitations of databases. Searches were performed using Boolean OR and AND operators between the main terms and keywords of particular topic of the subject under investigation. All retrospective, prospective, cohort, and pilot studies were included, which were provided with more details about the topic. Articles such as letter to the editor, review, and short communications were excluded because of lack of information, discussions, or use of radiogenomics method on other cancers. For quality assessment of articles, STROBE checklist was used.

Result

For the systematic review, 18 articles were approved after assessing the full text of selected articles. In this review, 3614 patients with BC of selected articles were evaluated, and all radiogenomics were associated with more power in classification, differential diagnosis, and prognosis of BC. Among the various modalities to predict genomic indicators and molecular subtypes, DCE-MRI has the higher performance and finally the highest amount of AUC value (0.956) belonged to PI3K gene.

Conclusion

This review shows that radiogenomics can help with the diagnosis and treatment of breast cancer in patients. It has shown that recognizing and specifying radiogenomic phenotypes in the genomic signatures can be helpful in treatment and diagnosis of disease. The molecular methods used in these articles are limited to miRNAs expression, gene expression, Ki67 proliferation index, next-generation RNA sequencing, whole RNA sequencing, and molecular histopathology that can be completed in future studies by other methods such as exosomal miRNAs, specific proteins expression, DNA repair capacity, and other biomarkers that have prognostic and predictive value for cancer treatment response. Studies with control group and large sample size for evaluation of radiogenomics in diagnosis and treatment recommended.

The Predictive Effect of the 8th AJCC Pathological Prognostic Staging on the Benefit of Postmastectomy Radiotherapy in N2/N3 Breast Cancer

Background

The role of the 8th American Joint Committee on Cancer (AJCC) pathological prognostic staging (PPS) on treatment-decision making of breast cancer (BC) remains unclear. This study aimed to investigate the predictive effect of the 8th AJCC PPS on the benefit of postmastectomy radiotherapy (PMRT) in N2/N3 BC.

Methods

We included women with stage N2/3 BC diagnosed between 2010 and 2018 from the Surveillance, Epidemiology, and End Results database. The effect of PMRT on breast cancer-specific survival (BCSS) was evaluated using the multivariate Cox proportional-hazards models.

Results

A total of 13,445 patients were identified, including 10,547 (78.4%) patients treated with PMRT. All patients had reassigned stages based on the 8th AJCC PPS. There were 7102 patients (52.8%) that had stage changed, including 1160 patients (8.6%) were upstaged and 5942 patients (44.2%) were downstaged from the 7th AJCC anatomical staging (AS) to the 8th AJCC PPS. Regarding the 7th AJCC AS, 7603 (56.5%), 948 (7.1%), and 4895 (36.4%) were stage IIIA, IIIB, and IIIC diseases, respectively. Using the 8th AJCC PPS, 3525 (26.2%), 460 (3.4%), 1335 (9.9%), 3457 (25.7%), 2169 (19.1%), and 2100 (15.6%) patients were restaged as IB, IIA, IIB, IIIA, IIIB, and IIIC diseases, respectively. The PPS displayed increased prognostic accuracy and improved model fit with respect to BCSS compared to the 7th AS (C-index, 0.731 vs 0.605, P < 0.001; Akaike Information Criterion, 42141 vs 43118). Regarding the AS, the receipt of PMRT was associated with a better BCSS in those with stage IIIA (P = 0.004), IIIB (P = 0.003), and IIIC (P < 0.001) diseases. Using the PPS, the receipt of PMRT was not associated with a better BCSS among patients with stage IB (P = 0.446), IIA (P = 0.140), and IIB (P = 0.248) disease, while the receipt of PMRT was associated with a better BCSS for those with stage IIIA (P = 0.009), IIIB (P < 0.001), and IIIC (P < 0.001) disease.

Conclusion

The 8th AJCC staging provides superior risk stratification and a better tool to predict the benefit of PMRT in N2/3 BC.

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

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

Thyroid dysfunctions and autoimmunity in breast cancer patients: a prospective case-control study

OBJECTIVE

The relationship of thyroid dysfunction and autoimmunity with breast cancer (BC) continues to be contentious. The primary aim of this study was to estimate the prevalence of thyroid dysfunctions and autoimmunity in BC patients, and the secondary aims were to investigate the relationship of thyroid dysfunction with the clinicopathological profile of and therapy received by BC patients.

METHODS

This was a single-center prospective case-control study (March 2015-May 2017). Women with BC (n = 191), age-matched healthy controls (n = 166) and malignant controls (patients with cervical cancer, n = 87) were enrolled. Basal serum free thyroxin (fT4), thyrotropin (TSH) and anti-thyroid peroxidase (TPO) antibody levels were measured in all three groups; fT4, TSH and TPO measures were repeated after chemotherapy and at the 1-year follow-up (one year after diagnosis) in the BC patients.

RESULTS

The prevalence of overall hypothyroidism and autoimmunity (p = 0.106) did not differ significantly between the three groups, but the rate of clinical hypothyroidism was significantly higher in the BC group than in the healthy control group and the malignant control group (12.2% vs. 3.0% vs. 4.6%, respectively; p = 0.001). BC patients had significantly lower mean basal TSH concentrations than the healthy controls (p = 0.017). The postchemotherapy TSH concentrations were significantly lower (p = 0.001), and the fT4 concentrations were higher, albeit not significantly (p = 1.00), than the respective basal concentrations. The reverse was true for the follow-up values, in which the TSH (p = 1.00) values were higher and the fT4 (p = 0.03) concentrations were lower than the respective basal concentrations. An additional 6% of the BC patients developed clinical hypothyroidism during follow-up. Hypothyroid (p = 0.02) and TPO-positive (p = 0.004) patients had significantly smaller tumors, but their other clinicopathological features were comparable to those without thyroid dysfunction.

CONCLUSION

The prevalence of clinical hypothyroidism requiring thyroxine replacement was significantly high in BC patients and increased further during follow-up. Hence, BC patients should be considered a high-risk group that should receive routine screening for hypothyroidism.

Effect of change in neck position on thyroid dose and volume in supraclavicular irradiation for breast cancer using conformal technique

Background and aim:

Radiation exposure to the thyroid gland during breast irradiation can lead to hypothyroidism and this can impact on the quality of life. The aim of this study was to analyse if there is any difference in the radiation dose received by the thyroid gland during supraclavicular irradiation for breast cancer, with two different neck positions—straight or when the head is turned to the contralateral side to the breast being treated, when using a conformal technique.

Materials and methods:

All patients who received chest wall/breast and supraclavicular irradiation for breast cancer in 2019 in our department were divided into two groups based on the neck position as SN (neck positioned straight) and TN (neck tilted to contralateral side). The volume of thyroid gland, the radiation dose and volume parameters for Dmax, Dmean, and V5 to V40 of the thyroid were tabulated.

Results:

There were 72 patients included in the study with a mean age of 59 years, with 39 in the SN group and 33 in the TN group. There was no significant difference in thyroid volume between the two groups. Dmean, V15, V20, V25, V30 and V35 were significantly lower in tilted neck patients as compared to straight neck patients.

Conclusion:

Neck positioned to the contralateral side of the breast primary may be recommended for conformal CT-based radiation planning.

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

BACKGROUND AND PURPOSE

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSION

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