Abdominal radiation and diabetes: one more piece in the puzzle

Diabetes in childhood cancer survivors: emerging concepts in pathophysiology and future directions

With advancements in cancer treatment and supportive care, there is a growing population of childhood cancer survivors who experience a substantial burden of comorbidities related to having received cancer treatment at a young age. Despite an overall reduction in the incidence of most chronic health conditions in childhood cancer survivors over the past several decades, the cumulative incidence of certain late effects, in particular diabetes mellitus (DM), has increased. The implications are significant, because DM is a key risk factor for cardiovascular disease, a leading cause of premature death in childhood cancer survivors. The underlying pathophysiology of DM in cancer survivors is multifactorial. DM develops at younger ages in survivors compared to controls, which may reflect an "accelerated aging" phenotype in these individuals. The treatment-related exposures (i.e., chemotherapy, radiation) that increase risk for DM in childhood cancer survivors may be more than additive with established DM risk factors (e.g., older age, obesity, race, and ethnicity). Emerging research also points to parallels in cellular processes implicated in aging- and cancer treatment-related DM. Still, there remains marked inter-individual variability regarding risk of DM that is not explained by demographic and therapeutic risk factors alone. Recent studies have highlighted the role of germline genetic risk factors and epigenetic modifications that are associated with risk of DM in both the general and oncology populations. This review summarizes our current understanding of recognized risk factors for DM in childhood cancer survivors to help inform targeted approaches for disease screening, prevention, and treatment. Furthermore, it highlights the existing scientific gaps in understanding the relative contributions of individual therapeutic exposures and the mechanisms by which they exert their effects that uniquely predispose this population to DM following cancer treatment.

Causal associations between site-specific cancer and diabetes risk: A two-sample Mendelian randomization study

BACKGROUND

Both cancer and diabetes are complex chronic diseases that have high economic costs for society. The co-occurrence of these two diseases in people is already well known. The causal effects of diabetes on the development of several malignancies have been established, but the reverse causation of these two diseases (e.g., what type of cancer can cause T2D) has been less investigated.

METHODS

Multiple Mendelian randomization (MR) methods, such as the inverse-variance weighted (IVW) method, weighted median method, MR-Egger, and MR pleiotropy residual sum and outlier test, were performed to evaluate the causal association of overall and eight site-specific cancers with diabetes risk using genome-wide association study summary data from different consortia, such as Finngen and UK biobank.

RESULTS

A suggestive level of evidence was observed for the causal association between lymphoid leukaemia and diabetes by using the IVW method in MR analyses (P = 0.033), indicating that lymphoid leukaemia increased diabetes risk with an odds ratio of 1.008 (95% confidence interval, 1.001-1.014). Sensitivity analyses using MR-Egger and weighted median methods showed consistent direction of the association compared with the IVW method. Overall and seven other site-specific cancers under investigation (i.e., multiple myeloma, non-Hodgkin lymphoma, and cancer of bladder, brain, stomach, lung, and pancreas) were not causally associated with diabetes risk.

CONCLUSIONS

The causal relationship between lymphoid leukaemia and diabetes risk points to the necessity of diabetes prevention amongst leukaemia survivors as a strategy for ameliorating the associated disease burden.

Incidence of Diabetes in the Atomic Bomb Survivors: 1969-2015

CONTEXT

Recent epidemiological studies have shown increased risk of diabetes among childhood cancer survivors who received high therapeutic doses of radiation, particularly to the total body or to the abdomen. However, the effect of low-to-moderate dose radiation (<4 Gy) on the risk of diabetes is still unknown.

OBJECTIVES

To investigate the radiation effect on diabetes incidence among atomic bomb (A-bomb) survivors, and whether the dose response is modified by other factors including city, sex, and age at time of bombing (ATB).

METHODS

9131 participants without diabetes at baseline were observed through biennial clinical exams from 1969 to 2015. A Cox proportional hazards model was used to estimate hazard ratios (HR) to evaluate the dose response for diabetes incidence.

RESULTS

During the study period, 1417 incident diabetes cases were identified. The overall crude incidence rate was 7.01/103 person-years. Radiation dose was significantly associated with diabetes incidence, with effect modification by city and age ATB. In Hiroshima, at ages 10 and 30 ATB, the HRs at 1 Gy of pancreatic radiation dose were 1.47 (95% CI, 1.31-1.66) and 1.13 (95% CI, 0.97-1.31), respectively. However, no significant radiation dose response was observed at these ages in Nagasaki. The HR for radiation dose was higher among those who were younger ATB and decreased 1% for each additional year of age.

CONCLUSIONS

Among A-bomb survivors, a radiation association was suggested for incidence of diabetes. Results were inconsistent by city and age ATB, which could indicate potential confounding of the radiation association with diabetes.

Frequency of obesity and metabolic syndrome in childhood leukemia and lymphoma survivors

OBJECTIVES

In this study, it was aimed to determine the prevalence and clinical features of obesity and metabolic syndrome, which are long-term effects of survivors after treatment in children with leukemia and lymphoma.

PATIENTS AND METHODS

Patients with leukemia and lymphoma, who were diagnosed between 2000 and 2012 (at least 2 two years after remission) were included. Data obtained through reviewing the family history, demographic characteristics, anthropometric measurements, and laboratory parameters (blood glucose, lipid, and insulin levels) were analyzed and compared at the time of diagnosis, after the treatment and at time of the study.

RESULTS

Eighty nine patients (45 boys, 44 girls) were included (mean age: 14.7 ± 4.3 years): 77.5% had acute lymphoblastic leukemia, 11.2% had acute myeloid leukemia, and 11.2% had lymphoma. Overall, 46% patients had received radiotherapy, 7% had undergone surgery, and 2.2% had received stem cell transplantation in addition to chemotherapy. The mean duration of treatment was 2.4 years, and the time elapsed after treatment was 4.9 years. While only one had obesity at the diagnosis, a significant increase in obesity (20%), hypertension (15.7%), hyperglycemia (15%), insulin resistance (35%) were observed at the time of study, and family history of hypertension, dyslipidemia, and cardiovascular diseases were significantly higher in this subgroup.

CONCLUSION

The prevalence of metabolic syndorme is higher in children with leukemia and lymphoma after treatment, and begins to increase with the initiation of treatment and continues to increase over time. These children should be followed-up for late-effects including metabolic syndrome through life-long period.

Induced Torpor as a Countermeasure for Low Dose Radiation Exposure in a Zebrafish Model

The development of the Artemis programme with the goal of returning to the moon is spurring technology advances that will eventually take humans to Mars and herald a new era of interplanetary space travel. However, long-term space travel poses unique challenges including exposure to ionising radiation from galactic cosmic rays and potential solar particle events, exposure to microgravity and specific nutritional challenges arising from earth independent exploration. Ionising radiation is one of the major obstacles facing future space travel as it can generate oxidative stress and directly damage cellular structures such as DNA, in turn causing genomic instability, telomere shortening, extracellular-matrix remodelling and persistent inflammation. In the gastrointestinal tract (GIT) this can lead to leaky gut syndrome, perforations and motility issues, which impact GIT functionality and affect nutritional status. While current countermeasures such as shielding from the spacecraft can attenuate harmful biological effects, they produce harmful secondary particles that contribute to radiation exposure. We hypothesised that induction of a torpor-like state would confer a radioprotective effect given the evidence that hibernation extends survival times in irradiated squirrels compared to active controls. To test this hypothesis, a torpor-like state was induced in zebrafish using melatonin treatment and reduced temperature, and radiation exposure was administered twice over the course of 10 days. The protective effects of induced-torpor were assessed via RNA sequencing and qPCR of mRNA extracted from the GIT. Pathway and network analysis were performed on the transcriptomic data to characterise the genomic signatures in radiation, torpor and torpor + radiation groups. Phenotypic analyses revealed that melatonin and reduced temperature successfully induced a torpor-like state in zebrafish as shown by decreased metabolism and activity levels. Genomic analyses indicated that low dose radiation caused DNA damage and oxidative stress triggering a stress response, including steroidal signalling and changes to metabolism, and cell cycle arrest. Torpor attenuated the stress response through an increase in pro-survival signals, reduced oxidative stress via the oxygen effect and detection and removal of misfolded proteins. This proof-of-concept model provides compelling initial evidence for utilizing an induced torpor-like state as a potential countermeasure for radiation exposure.

Ionizing radiation-induced circulatory and metabolic diseases

Risks to health are the prime consideration in all human situations of ionizing radiation exposure and therefore of relevance to radiation protection in all occupational, medical, and public exposure situations. Over the past few decades, advances in therapeutic strategies have led to significant improvements in cancer survival rates. However, a wide range of long-term complications have been reported in cancer survivors, in particular circulatory diseases and their major risk factors, metabolic diseases. However, at lower levels of exposure, the evidence is less clear. Under real-life exposure scenarios, including radiotherapy, radiation effects in the whole organism will be determined mainly by the response of normal tissues receiving relatively low doses, and will be mediated and moderated by systemic effects. Therefore, there is an urgent need for further research on the impact of low-dose radiation. In this article, we review radiation-associated risks of circulatory and metabolic diseases in clinical, occupational or environmental exposure situations, addressing epidemiological, biological, risk modelling, and systems biology aspects, highlight the gaps in knowledge and discuss future directions to address these gaps.

Long-Term Endocrine and Metabolic Consequences of Cancer Treatment: A Systematic Review

The number of patients surviving ≥5 years after initial cancer diagnosis has significantly increased during the last decades due to considerable improvements in the treatment of many cancer entities. A negative consequence of this is that the emergence of long-term sequelae and endocrine disorders account for a high proportion of these. These late effects can occur decades after cancer treatment and affect up to 50% of childhood cancer survivors. Multiple predisposing factors for endocrine late effects have been identified, including radiation, sex, and age at the time of diagnosis. A systematic literature search has been conducted using the PubMed database to offer a detailed overview of the spectrum of late endocrine disorders following oncological treatment. Most data are based on late effects of treatment in former childhood cancer patients for whom specific guidelines and recommendations already exist, whereas current knowledge concerning late effects in adult-onset cancer survivors is much less clear. Endocrine sequelae of cancer therapy include functional alterations in hypothalamic-pituitary, thyroid, parathyroid, adrenal, and gonadal regulation as well as bone and metabolic complications. Surgery, radiotherapy, chemotherapy, and immunotherapy all contribute to these sequelae. Following irradiation, endocrine organs such as the thyroid are also at risk for subsequent malignancies. Although diagnosis and management of functional and neoplastic long-term consequences of cancer therapy are comparable to other causes of endocrine disorders, cancer survivors need individually structured follow-up care in specialized surveillance centers to improve care for this rapidly growing group of patients.

Insulin and glucose homeostasis in childhood cancer survivors treated with abdominal radiation: A pilot study

BACKGROUND

Childhood cancer survivors exposed to abdominal radiation (abdRT) are at increased risk for both insulin-dependent and non-insulin-dependent diabetes. We sought to clarify the pathophysiology of diabetes after abdRT by performing dynamic studies of insulin and glucose and testing for type 1 diabetes-associated autoantibodies.

PROCEDURE

Cross-sectional analysis of 2-year childhood cancer survivors treated with abdRT at age ≤21 years who underwent oral glucose tolerance testing and assessment of diabetes-related autoantibodies from December 2014 to September 2016. Prevalence of insulin/glucose derangements, indices of insulin sensitivity/secretion (homeostatic model assessment of insulin resistance [HOMA-IR], whole-body insulin sensitivity, insulinogenic index), autoantibody positivity, and treatment/demographic factors associated with adverse metabolic outcomes were assessed.

RESULTS

Among 40 participants previously exposed to abdRT (57.5% male; median age at cancer diagnosis, 3.3 years [range, 0.5-20.1]; median age at study 14.3 years [range, 8.3-49.8]; none with obesity), 9 (22.5%) had glucose derangements (n = 4 with impaired fasting glucose [≥100 mg/dL]; n = 4 with impaired glucose tolerance [2-hour glucose 140-199 mg/dL]; n = 1 with previously unrecognized diabetes [2-hour glucose ≥200 mg/dL]). Three of the four individuals with impaired fasting glucose also had insulin resistance, as measured by HOMA-IR; an additional four subjects with normal glucose tolerance were insulin resistant. The subject with diabetes had normal HOMA-IR. No participant had absolute insulinopenia or >1 positive diabetes-related autoantibody.

CONCLUSIONS

This study suggests that radiation-induced damage to the insulin-producing β-cells is an unlikely explanation for the early derangements in glucose metabolism observed after abdRT. Research into alternative pathways leading to diabetes after abdRT is needed.

Risk of diabetes after para-aortic radiation for testicular cancer

Background

While the risk of diabetes is increased following radiation exposure to the pancreas among childhood cancer survivors, its association among testicular cancer (TC) survivors has not been investigated.

Methods

Diabetes risk was studied in 2998 1-year TC survivors treated before 50 years of age with orchidectomy with/without radiotherapy between 1976 and 2007. Diabetes incidence was compared with general population rates. Treatment-specific risk of diabetes was assessed using a case–cohort design.

Results

With a median follow-up of 13.4 years, 161 TC survivors were diagnosed with diabetes. Diabetes risk was not increased compared to general population rates (standardised incidence ratios (SIR): 0.9; 95% confidence interval (95% CI): 0.7–1.1). Adjusted for age, para-aortic radiotherapy was associated with a 1.66-fold (95% CI: 1.05–2.62) increased diabetes risk compared to no radiotherapy. The excess hazard increased with 0.31 with every 10 Gy increase in the prescribed radiation dose (95% CI: 0.11–0.51, P = 0.003, adjusted for age and BMI); restricted to irradiated patients the excess hazard increased with 0.33 (95% CI: −0.14 to 0.81, P = 0.169) with every 10 Gy increase in radiation dose.

Conclusion

Compared to surgery only, para-aortic irradiation is associated with increased diabetes risk among TC survivors.

Obesity and Metabolic Disease After Childhood Cancer

As care for the childhood cancer patient has improved significantly, there is an increasing incidence of treatment-related late effects. Obesity and type 2 diabetes mellitus are common and significant metabolic conditions in some populations of adult survivors of childhood cancer. Results from the Childhood Cancer Survivor Study and other large cohorts of childhood cancer survivors reveal that long-term survivors of acute lymphoblastic leukemia and those who received total body irradiation or abdominal radiotherapy are at highest risk. The potential mechanisms for the observed increase in risk, including alterations in leptin and adiponectin, pancreatic insufficiency, poor dietary habits, sedentary lifestyle, and perhaps changes in the composition of the gut microbiota, are reviewed. Discussion of exercise and diet intervention studies shows that further research about the barriers to a healthy lifestyle and other interventions in childhood cancer survivors is warranted.

Type 2 Diabetes is a Delayed Late Effect of Whole-Body Irradiation in Nonhuman Primates

One newly recognized consequence of radiation exposure may be the delayed development of diabetes and metabolic disease. We document the development of type 2 diabetes in a unique nonhuman primate cohort of monkeys that were whole-body irradiated with high doses (6.5-8.4 Gy) 5-9 years earlier. We report here a higher prevalence of type 2 diabetes in irradiated monkeys compared to age-matched nonirradiated monkeys. These irradiated diabetic primates demonstrate insulin resistance and hypertriglyceridemia, however, they lack the typical obese presentation of primate midlife diabetogenesis. Surprisingly, body composition analyses by computed tomography indicated that prior irradiation led to a specific loss of visceral fat mass. Prior irradiation led to reductions in insulin signaling effectiveness in skeletal muscle and higher monocyte chemoattractant protein 1 levels, indicative of increased inflammation. However, there was an absence of large defects in pancreatic function with radiation exposure, which has been documented previously in animal and human studies. Monkeys that remained healthy and did not become diabetic in the years after irradiation were significantly leaner and smaller, and were generally smaller and younger at the time of exposure. Irradiation also resulted in smaller stature in both diabetic and nondiabetic monkeys, compared to nonirradiated age-matched controls. Our study demonstrates that diabetogenesis postirradiation is not a consequence of disrupted adipose accumulation (generalized or in ectopic depots), nor generalized pancreatic failure, but suggests that peripheral tissues such as the musculature are impaired in their response to insulin exposure. Ongoing inflammation in these animals appears to be a consequence of radiation exposure and can interfere with insulin signaling. The reasons that some animals remain protected from diabetes as a late effect of irradiation are not clear, but may be related to body size. The translational relevance for these results suggest that muscle may be an important and underappreciated target organ for the delayed late effect of whole-body irradiation, leading to increased risk of insulin resistance and diabetes development.

Risk of diabetes mellitus in long-term survivors of Hodgkin lymphoma

PURPOSE

Recently, an increased risk of diabetes mellitus (DM) was observed after abdominal irradiation for childhood cancer. Because many Hodgkin lymphoma (HL) survivors have also been treated with infradiaphragmatic radiotherapy, we evaluated the association between HL treatment and DM risk.

PATIENTS AND METHODS

Our study cohort comprised 2,264 5-year HL survivors, diagnosed before age 51 years and treated between 1965 and 1995. Treatment and follow-up information was collected from medical records and general practitioners. Radiation dosimetry was performed to estimate radiation dose to the pancreas. Cumulative incidence of DM was estimated, and risk factors for DM were evaluated by using Cox regression.

RESULTS

After a median follow-up of 21.5 years, 157 patients developed DM. Overall cumulative incidence of DM after 30 years was 8.3% (95% CI, 6.9% to 9.8%). After para-aortic radiation with ≥ 36 Gy, the 30-year cumulative incidence of DM was 14.2% (95% CI, 10.7% to 18.3%). Irradiation with ≥ 36 Gy to the para-aortic lymph nodes and spleen was associated with a 2.30-fold increased risk of DM (95% CI, 1.54- to 3.44-fold) whereas para-aortic radiation alone with ≥ 36 Gy was associated with a 1.82-fold increased risk (95% CI, 1.02- to 3.25-fold). Lower doses (10 to 35 Gy) did not significantly increase risk of DM. The risk of DM significantly increased with higher mean radiation doses to the pancreatic tail (P < .001).

CONCLUSION

Radiation to the para-aortic lymph nodes increases the risk of developing DM in 5-year HL survivors. Screening for DM should be considered in follow-up guidelines for HL survivors, and treating physicians should be alert to this increased risk.