Breast cancer incidence in the regions of Belarus and Ukraine most contaminated by the Chernobyl accident: 1978 to 2016

Personal history of irradiation and risk of breast cancer: A Mendelian randomisation study

Background

Studies on the relationship between personal history of irradiation and breast cancer have been reported for a long time. Still, epidemiological studies have not been conclusive, and the causal relationship is unclear. To address this issue, we employed Mendelian randomisation (MR) analysis to examine the association between individual radiation exposure history and breast cancer.

Methods

We used a series of quality control methods to select single nucleotide polymorphism (SNP) closely related to exposure. Meanwhile, several analysis methods were used to analyse the sample data to make the conclusion more reliable. To evaluate the horizontal pleiotropy, heterogeneity and stability of SNPs for breast cancer, the MR-Egger intercept test, Cochran's Q test and 'leave one' sensitivity analysis were used. Finally, the outlier variation determined by the Mendelian Randomisation Pleiotropy RESidual Sum and Outlier test is gradually eliminated to reduce the influence of heterogeneity and horizontal pleiotropy.

Results

After implementing rigorous quality control procedures, we carefully chose 102 qualified instrumental variables closely associated with the selected exposure for sensitivity analysis. This was conducted to evaluate the heterogeneity, level multiplicity, and stability of SNPs in the context of personal radiation history and its correlation with breast cancer. The results of the inverse variance weighted method analysis revealed a positive correlation between personal radiation and a heightened risk of breast cancer (odds ratio (OR) = 1.52; 95% confidence interval (CI) = 1.30-1.77). We also validated on another data set; the results were similar (OR = 1.51; 95% CI = 1.27-1.81). Furthermore, the findings from the sensitivity analysis were consistent. At the genetic level, our research demonstrated that personal radiation exposure is associated with an elevated risk of breast cancer.

Conclusions

Using genetic data provides evidence and strengthens the causal link that personal radiation causes breast cancer.

A Historical Survey of Key Epidemiological Studies of Ionizing Radiation Exposure

In this article we review the history of key epidemiological studies of populations exposed to ionizing radiation. We highlight historical and recent findings regarding radiation-associated risks for incidence and mortality of cancer and non-cancer outcomes with emphasis on study design and methods of exposure assessment and dose estimation along with brief consideration of sources of bias for a few of the more important studies. We examine the findings from the epidemiological studies of the Japanese atomic bomb survivors, persons exposed to radiation for diagnostic or therapeutic purposes, those exposed to environmental sources including Chornobyl and other reactor accidents, and occupationally exposed cohorts. We also summarize results of pooled studies. These summaries are necessarily brief, but we provide references to more detailed information. We discuss possible future directions of study, to include assessment of susceptible populations, and possible new populations, data sources, study designs and methods of analysis.

Impact of Disasters on Older Adult Cancer Outcomes: A Scoping Review

PURPOSE

There is an urgent need to address the growing global cancer burden in the context of complex disaster events, which both disrupt access to oncology care and facilitate carcinogenic exposures. Older adults (65 years and older) are a growing population with multifaceted care needs, making them especially vulnerable to disasters. The objective of this scoping review is to characterize the state of the literature concerning older adult cancer-related outcomes and oncologic care after a disaster event.

METHODS

A search was conducted in PubMed and Web of Science. Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for scoping reviews, articles were extracted and screened for inclusion. Eligible articles were summarized using descriptive and thematic analyses.

RESULTS

Thirty-five studies met all criteria for full-text review. The majority focused on technological disasters (60%, n = 21), followed by climate-amplified disasters (28.6%, n = 10) and geophysical disasters (11.4%, n = 4). Thematic analysis classified the current evidence into three major categories: (1) studies concerned with carcinogenic exposure and cancer incidence related to the disaster event, (2) studies examining changes in access to cancer care and cancer treatment disruptions as a result of the disaster event, and (3) studies exploring the psychosocial experiences of patients with cancer affected by a disaster event. Few studies focused on older adults specifically, and most of the current evidence focuses on disasters in the United States or Japan.

CONCLUSION

Older adult cancer outcomes after a disaster event are understudied. Current evidence suggests that disasters worsen cancer-related outcomes among older adults by disrupting continuity of care and access to timely treatment. There is a need for prospective longitudinal studies following older adult populations postdisaster and studies focused on disasters in low- and middle-income country contexts.

The Effects of the Ukrainian Conflict on Oncological Care: The Latest State of the Art

BACKGROUND

The COVID-19 pandemic has dramatically affected all aspects of the patient's pathway to cancer diagnosis and subsequent treatment. Our main objective was to evaluate the status of cancer trials in Ukraine as of September 2022.

METHODS

Initially, we examined with a narrative review the state of breast, colorectal, and cervical cancer population-based screening. Subsequently, we assessed each trial status for the years 2021 and 2022.

RESULTS

Estimates of participation in breast and cervical cancer screening are different from region to region. Moreover, regarding cervical cancer screening, extremely different participation estimates were reported: 73% in 2003 vs. <10% 2020. Our data show that from 2014 to 2020, despite the pandemic, cancer trials in Ukraine significantly increased from 27 to 44. In 2021 no trials were completed; in fact, we observed that out of 41 trials, 8 were active not recruiting, 33 were recruiting, and 0 were completed or terminated. In 2022 in Ukraine, for oncological pathologies, only 3 trials were registered, while in 2021, 41 trials were registered. The suspension of trials regarded above all concern hematological tissue (66.7%) and the genitourinary tract (60%).

CONCLUSIONS

Our work has highlighted how the areas most affected by the conflict present criticalities in oncological care.

Breast cancer risk in Ukrainian women exposed to Chornobyl fallout while pregnant or lactating: standardized incidence ratio analysis, 1998 to 2016

The radiation-related risk of breast cancer among women following the Chornobyl accident remains uncertain. During pregnancy, there is rapid cell proliferation in the breast while radioactive iodine from fallout exposure can concentrate in lactating breast tissues. We conducted a standardized incidence ratio (SIR) analysis of breast cancer in a cohort of 2,631 women who were lactating and/or pregnant at any time during the 2-month period of radioiodine fallout (April 26, 1986-June 30, 1986). There were 37,151 person-years of follow-up, and 26 incident breast cancers were identified through linkage with the National Cancer Registry of Ukraine. Breast cancer rates among pregnant or lactating women were compared to the general population rates, and SIRs were adjusted for oblast, urban/rural, age, and calendar year. The SIR was not significant for women pregnant at the time of the accident (SIR = 0.75; 95% CI 0.44, 1.18) or for women lactating anytime within 2 months of the accident (SIR = 0.96; 95% CI 0.48, 1.68). However, there was a non-significantly elevated risk for women lactating at the time of accident (SIR = 1.30, 95% CI 0.40, 3.01). The increased SIR for breast cancer among lactating women is consistent with the results of a similar study in Belarus and indicates the need to quantify the radiation risk of breast cancer in a larger study of women lactating during the period of fallout exposure.

Cervical and Endometrial Cancer Incidence in the Female Population from the Bryansk Region Living in Conditions of Chemical, Radioactive and Combined Environmental Contamination (2000-2020)

At the end of 36 years after the Chernobyl disaster, about 5 million people still live in the radioactively contaminated territories of Russia, Ukraine, and Belarus, and the density of radioactive contamination by Cesium-137 and Strontium-90 will remain radiologically significant for decades. We assessed cervical and endometrial cancer primary incidence (new cases) in the female population from the Bryansk region living in conditions of chemical, radioactive, and combined environmental contamination for 2000−2020. We found a significant increase in the long-term trend in the primary incidence of cervical and endometrial cancer in all the studied groups, regardless of the environmental conditions of residence (p < 0.00001). We did not find statistically significant differences in the incidence of cervical and endometrial cancer in women, regardless of the level of chemical, radioactive, and combined environmental contamination. However, women living in environmentally unfavorable areas (in total, in the territories of chemical, radioactive, and combined contamination) are statistically significantly more likely to develop endometrial cancer in terms of relative risk compared to environmentally safe (control) areas (RR 1.17 (1.08−1.27)). No such pattern was found for cervix cancer. It should be noted, since environmentally safe (control) areas have a certain level of contamination (albeit low), RR is underestimated.

Low Dose and Non-Targeted Radiation Effects in Environmental Protection and Medicine-A New Model Focusing on Electromagnetic Signaling

The role of signalling in initiating and perpetuating effects triggered by deposition of ionising radiation energy in parts of a system is very clear. Less clear are the very early steps involved in converting energy to chemical and biological effects in non-targeted parts of the system. The paper aims to present a new model, which could aid our understanding of the role of low dose effects in determining ultimate disease outcomes. We propose a key role for electromagnetic signals resulting from physico-chemical processes such as excitation decay, and acoustic waves. These lead to the initiation of damage response pathways such as elevation of reactive oxygen species and membrane associated changes in key ion channels. Critically, these signalling pathways allow coordination of responses across system levels. For example, depending on how these perturbations are transduced, adverse or beneficial outcomes may predominate. We suggest that by appreciating the importance of signalling and communication between multiple levels of organisation, a unified theory could emerge. This would allow the development of models incorporating time, space and system level to position data in appropriate areas of a multidimensional domain. We propose the use of the term "infosome" to capture the nature of radiation-induced communication systems which include physical as well as chemical signals. We have named our model "the variable response model" or "VRM" which allows for multiple outcomes following exposure to low doses or to signals from low dose irradiated cells, tissues or organisms. We suggest that the use of both dose and infosome in radiation protection might open up new conceptual avenues that could allow intrinsic uncertainty to be embraced within a holistic protection framework.

Doses from external irradiation and ingestion of 134Cs, 137Cs and 90Sr of the population of Belarus accumulated over 35 years after the Chernobyl accident

This study considers the exposure of the population of the most contaminated Gomel and Mogilev Oblasts in Belarus to prolonged sources of irradiation resulting from the Chernobyl accident. Dose reconstruction methods were developed and applied in this study to estimate the red bone-marrow doses (RBMs) from (i) external irradiation from gamma-emitting radionuclides deposited on the ground and (ii) ¹³⁴Cs, ¹³⁷Cs and ⁹⁰Sr ingestion with locally produced foodstuffs. The mean population-weighted RBM doses accumulated during 35 years after the Chernobyl accident were 12 and 5.7 mGy for adult residents in Gomel and Mogilev Oblasts, respectively, while doses for youngest age groups were 20-40% lower. The highest mean area-specific RBM doses for adults accumulated in 1986-2021 were 63, 56 and 46 mGy in Narovlya, Vetka and Korma raions in Gomel Oblast, respectively. For most areas, external irradiation was the predominant pathway of exposure (60-70% from the total dose), except for areas with an extremely high aggregated ¹³⁷Cs soil to cow's milk transfer coefficient (≥ 5.0 Bq L^-1 per kBq m^-2), where the contribution of ¹³⁴Cs and ¹³⁷Cs ingestion to the total RBM dose was more than 70%. The contribution of ⁹⁰Sr intake to the total RBM dose did not exceed 4% for adults and 10% for newborns in most raion in Gomel and Mogilev Oblasts. The validity of the doses estimated in this study was assessed by comparison with doses obtained from measurements by thermoluminescence dosimeters and whole-body counters done in 1987-2015. The methodology developed in this study can be used to calculate doses to target organs other than RBM such as thyroid and breast doses. The age-dependent and population-weighted doses estimated in this study are useful for ecological epidemiological studies, for projection of radiation risk, and for justification of analytical epidemiological studies in populations exposed to Chernobyl fallout.

Breast cancer risk in residents of Belarus exposed to Chernobyl fallout while pregnant or lactating: standardized incidence ratio analysis, 1997 to 2016

BACKGROUND

Pregnancy and lactation may constitute radiation-sensitive reproductive periods due to rapid cell proliferation and concentration of radioiodine in the lactating breast. However, there are limited epidemiological data among women exposed to radiation during these periods.

METHODS

We examined incidence of breast cancer in a cohort of 3214 women who were pregnant and/or lactating within 2 months (26 April to 30 June 1986) of the Chernobyl accident and residing in contaminated regions of Belarus. There were 33 breast cancers identified through linkage with the Belarusian National Cancer Registry. Breast cancer rates among women who were either pregnant and/or lactating were compared with population rates by calculating standardized incidence ratios (SIR) and 95% confidence intervals (CI) adjusting for attained age, oblast, urban/rural residence and calendar year.

RESULTS

Among women who were lactating, we found a greater than 2-fold increased risk of breast cancer compared with the general population, SIR = 2.49 (95% CI: 1.55, 3.75). In contrast, women who were pregnant were not at increased risk (SIR = 0.84 95% CI: 0.46, 1.38). The SIR was highest in women who were exposed at a younger age and at the earliest time period since the accident, though stratified analyses had limited sample sizes.

CONCLUSIONS

We found a significantly increased risk of breast cancer among women residing in contaminated areas of Belarus who were lactating at the time of the accident and may have had elevated exposure to radioiodine, when compared with the general population. Studies of breast cancer with individual radiation dose estimates among women exposed during lactation are warranted.

Ovarian Malignancies Frequency in the Female Population from the Bryansk Region Living in Conditions of Radioactive, Chemical and Combine Contamination (2000-2020)

Background: Radioactive contamination and chemical pollution of the environment can affect the processes of carcinogenesis, including the formation of malignant neoplasms of the ovaries in women. We used the data of official state statistics for 2000–2020 to test the hypothesis about the effect of radioactive contamination (following the Chernobyl disaster) and chemical pollutants on the incidence of ovarian malignancies in the female population of the Bryansk region. Methods: A variety of statistical approaches were used to estimate the incidence of ovarian malignancies, including the Shapiro–Wilk test, Mann–Whitney U test, Spearman’s rank correlation test and linear regression. Results: We did not establish statistically significant differences in the frequency of primary morbidity of women with malignant neoplasms of the ovaries, regardless of the environmental conditions of living. Furthermore, no significant correlations were found between the frequency of primary morbidity of ovarian malignancies, both with the level of contamination by Cesium-137 and Strontium-90, and air pollution with volatile organic compounds, carbon monoxide, sulfur dioxide and nitrogen oxides. A statistically significant increase in the long-term trend in the frequency of ovarian malignant neoplasms was revealed in the areas of chemical pollution (p = 0.02), however, in other territories, no statistically significant regularities were established. The forecast of the frequency of newly diagnosed malignant neoplasms of the ovaries on average in the Bryansk region shows an increase of 12.4% in 2020 in comparison with the real data for 2020, while the largest increase in predicted values is recorded in the territories of radioactive contamination (by 79.6%), and the least in the combined territories (by 6.9%). Conclusions: The results obtained indicate the need for further work to understand the trends in the presence/absence of independent and combined effects of pollutants and the growth of oncogynecological pathology from the perspective of assessing the distant and regional metastasis, histological and immunohistochemical profile of a specific malignant ovarian neoplasm with levels of environmental contamination.

Comparative pathological characteristics of papillary thyroid carcinoma with second primary non-thyroid malignancies in the region affected by the Chernobyl accident

The aim was to study the pathological features of papillary thyroid carcinoma diagnosed with or before second primary malignancy in patients exposed to post-Chernobyl exposure. The patients selected (n = 6559) were those exposed to radiation at the age of ≤ 18 years old and developed papillary thyroid carcinoma during the years 1990-2020. Of these, 2.1% (n = 140) had second primary malignancies. To compare the histopathological characteristics of papillary thyroid carcinoma in the group under analysis, 91% (n = 128) with sufficient data were included in further analysis. The control group was formed by matching patients with age at exposure to radiation, age at surgery, gender, and place of residence. Median age at exposure was 14 years old for both groups. Besides, no difference in tumour extension and histological features of papillary thyroid carcinoma was noted between patients with synchronous or metachronous primary malignant tumours. Nevertheless, the time lag to the diagnosis of papillary thyroid carcinoma was shortened in the group with metachronous when compared to patients with synchronous second primaries (p < 0.001). Independent differences between patients with second primaries and their matched peers included tumour size {OR (95%CI) = 0.89 (0.45; 1.04)}, multiple tumours {OR (95% CI) = 1.46 (0.86; 2.42)}, lymphatic vessel invasion (OR (95%CI) 0.92 (0.61; 1.53)), blood vessel invasion (OR (95%CI) 0.41 (0.10; 1.23) and presence of numerous psammomas (OR (95%CI) 0.73 (0.39; 1.31)). The possible influence of radiative iodine treatment for development of second primaries was analysed for the group of patients with metachronous malignancies using the same approach (84 patients were compared to 252 matched patients). Independent differences also included tumour size {OR (95% CI) 0.77 (0.45; 1.30)}, lymphatic vessel invasion {OR (95%CI) 0.75(0.43; 1.28)}, blood vessel invasion {OR (95%CI) 0.17 (0.01; 0.87)}. Besides, multiple tumours were revealed more frequently in patients with metachronous primaries (OR (95%CI) 1.92 (1.0; 3.62)). To conclude, patients exposed to Chernobyl irradiation with the development of papillary thyroid carcinoma and second primary malignancy have less biological aggressive pathological characteristics of their thyroid cancers. Accordingly, these patients were less frequently treated with post-surgical radioactive iodine. Thus, 131I-irradiation may have negligible impact on the development of second primaries.