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

Risk of type 2 diabetes after breast cancer treatment: a population-based cohort study in Denmark

PURPOSE

Data on type 2 diabetes (T2D) risk after breast cancer (BC) could guide preventive strategies. Yet, studies had limitations regarding sample size, follow-up, and contemporary treatments. We evaluated the risk of T2D after BC overall, by cancer treatment, and compared with a matched cohort of cancer-free women.

METHODS

We assembled a population-based cohort of early-stage BC patients aged 30 years or more diagnosed during 1996-2021 in Denmark. We created a comparison cohort of 5 cancer- and T2D-free women for each BC patient, matched 6 months after BC diagnosis date on age and region. We followed both cohorts until T2D diagnosis, emigration, death, or December 31, 2022. We computed 5-year cumulative incidences and used Cox models to calculate time-varying adjusted hazard ratios (aHR) of T2D.

RESULTS

Among 74 526 BC survivors and 372 630 matched cancer-free women, 5-year cumulative incidences of T2D were 3.8% (95% confidence interval [CI] = 3.7 to 3.9) and 3.3% (95% CI = 3.3 to 3.4), respectively. The aHR of T2D was elevated but attenuated over follow-up (aHR5-years = 1.20, 95% CI = 1.15 to 1.25, and aHR15-years = 1.09, 95% CI = 1.05 to 1.12). Adjuvant endocrine therapy (aHR = 1.14; 95% CI = 1.10 to 1.19), aromatase inhibitors (aHR = 1.25; 95% CI = 1.18 to 1.32), and less so tamoxifen (aHR = 1.05; 95% CI = 0.99 to 1.11), were associated with elevated risk of T2D in women with BC vs cancer-free women. Among BC patients, chemotherapy (aHR = 1.10, 95% CI = 1.03 to 1.17) and radiation therapy (right-sided aHR = 1.18, 95% CI = 1.09 to 1.27 and left-sided aHR = 1.24, 95CI = 1.15 to 1.33) were associated with increased T2D risk.

CONCLUSION

BC was associated with excess risk of T2D, although of lower magnitude than previously reported. The excess risk was temporary and related to BC treatment but could also be influenced by obesity and heightened T2D diagnostic activity.

[Long-term organ toxicity of oncological therapies]

Cancer treatments, although life prolonging, are associated with side effects. The occurrence, duration, and severity of side effects vary, depending on treatment received. Long-term effects refer to effects that manifest during treatment and persist long after treatment has ended. Late effects are complications that occur after treatment has ended. These effects can have a negative impact on the functioning and quality of life of persons living with and beyond cancer. This overview aims to provide a non-exhaustive overview of the long-term and late effects associated with the traditional mainstay of cancer treatments (surgery, radiotherapy, chemotherapy) and newer treatments such as immunotherapy. In conclusion, long-term and late effects of cancer treatment can be associated with a high burden for those affected, including a reduction in their ability to function and health-related quality of life. Given the large and further growing number of cancer survivors and the abundance of long-term and late effects, it is essential to develop and implement risk-adapted, multidisciplinary survivorship care programmes.

Automated segmentation in planning-CT for breast cancer radiotherapy: A review of recent advances

Postoperative radiotherapy (RT) has been shown to effectively reduce disease recurrence and mortality in breast cancer (BC) treatment. A critical step in the planning workflow is the accurate delineation of clinical target volumes (CTV) and organs-at-risk (OAR). This literature review evaluates recent advancements in deep-learning (DL) and atlas-based auto-contouring techniques for CTVs and OARs in BC planning-CT images for RT. It examines their performance regarding geometrical and dosimetric accuracy, inter-observer variability, and time efficiency. Our findings indicate that both DL- and atlas-based methods generally show comparable performance across OARs and CTVs, with DL methods slightly outperforming in consistency and accuracy. Auto-segmentation of breast and most OARs achieved robust results in both segmentation quality and dosimetric planning. However, lymph node levels (LNLs) presented the greatest challenge in auto-segmentation with significant impact on dosimetric planning. The translation of these findings into clinical practice is limited by the geometric performance metrics and the lack of dose evaluation studies. Additionally, auto-contouring algorithms showed diverse structure sets, while training datasets varied in size, origin, patient positioning and imaging protocols, affecting model sensitivity. Guideline inconsistencies and varying definitions of ground truth led to substantial variability, suggesting a need for a reliable consensus training dataset. Finally, our review highlights the popularity of the U-Net architecture. In conclusion, while automated contouring has proven efficient for many OARs and the breast-CTV, further improvements are necessary in LNL delineation, dosimetric analysis, and consensus building.

Chemotherapy for post-menopausal women with early breast cancer seems not to result in clinically significant changes in thyroid function

OBJECTIVE

Adjuvant chemotherapy is often indicated in patients diagnosed with early breast cancer (EBC). Among others, weight gain is one of the observed side effects of both chemotherapy and other cancer treatments; however, the mechanism is not well-described. In this study, we aimed to assess thyroid function before and shortly after the course of chemotherapy for EBC.

METHODS

This is a prospective cohort study of women diagnosed with EBC. The main outcome was the thyroid function and body weight before and after completing chemotherapy. Secondary outcomes were the presence of thyroid autoantibodies and treatment radiation dosage. We included 72 patients treated with adjuvant chemotherapy, whereas 59 patients also received supraclavicular locoregional radiotherapy. Triple-negative breast cancer (BC) patients receiving chemoimmunotherapy were excluded.

RESULTS

After the chemotherapy, we observed an increase in thyroid-stimulating hormone (p = 0.03) and a decrease in free-thyroxine (p = 0.0006), with no significant weight change. The prevalence of autoimmune thyroiditis was low. On average 3 months post-chemo, we found no statistically significant difference in the thyroid function of women treated versus not treated with supraclavicular locoregional radiotherapy.

CONCLUSIONS

Although statistically significant changes in thyroid hormones were observed, this study suggests no obvious clinically significant changes in thyroid function in women with early BC after the course of chemotherapy. The decrease in thyroid function was not related to autoimmunity, non-thyroidal illness, radiotherapy, or high-dose corticosteroids. Further studies with a longer follow-up of thyroid function after adjuvant chemotherapy and supraclavicular locoregional radiotherapy are needed.

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.

Interactions between Polygenetic Variants and Lifestyle Factors in Hypothyroidism: A Hospital-Based Cohort Study

Hypothyroidism is a prevalent endocrine disorder and is associated with a variety of metabolic disturbances. This study aimed to investigate the polygenic variants associated with hypothyroidism risk and the interaction of polygenic risk scores (PRS) with dietary patterns in influencing disease risk in 56,664 participants aged >40 in a hospital-based cohort. The participants were classified as having hypothyroidism (n = 870) diagnosed by a physician and no hypothyroidism (n = 55,794). Genetic variants associated with hypothyroidism were identified using a genome-wide association study (GWAS). Genetic variants interacting with each other were selected using a generalized multifactor dimensionality reduction analysis, and the PRS generated was evaluated for interaction with lifestyle parameters. Coffee, alcohol, meat intake, and a Korean balanced diet were inversely associated with hypothyroidism risk, as were selenium, copper, and manganese intakes. White blood cell (WBC) counts and serum alkaline phosphatase and triglyceride concentrations were positively associated with hypothyroidism risk, as were osteoporosis and thyroid cancer. The GMDR analysis generated a three-single nucleotide polymorphism (SNP) model comprising dual oxidase-1 (DUOX1)_rs1648314; thyroid-stimulating hormone receptor (TSHR)_rs75664963; and major histocompatibility complex, class-II, DQ Alpha-1 (HLA-DQA1)_rs17426593. The PRS derived from the three- and seven-SNP models were associated with a 2.11- and 2.32-fold increase in hypothyroidism risk, respectively. Furthermore, the PRS from the three-SNP model showed interactions with WBC counts, wherein the positive association with hypothyroidism risk was more pronounced in participants with low WBC counts than those with high WBC counts (≥4 × 109 /L). Dietary patterns, such as the plant-based diet (PBD) and the Western-style diet (WSD), along with smoking status, exhibited interactions with the PRS, influencing hypothyroidism risk. In participants with a high PRS, those in the high-PBD, low-WSD, and smoker groups had a higher proportion of hypothyroidism than those in the low-PBD, high-WSD, and non-smoker groups. In conclusion, genetic variants related to immunity and thyroid hormone secretion were linked to hypothyroidism risk, and their PRS interacted with PBD and WSD intake and smoking status. These results contribute to a better understanding of hypothyroidism and its prevention strategies for precision medicine intervention.