Cancer incidence in atomic bomb survivors. Part II: Solid tumors, 1958-1987

[Does radiation therapy for prostate cancer increase the risk of second cancers?]

PURPOSE

The increased risk of second cancer after prostate radiotherapy is a debated clinical concern. The objective of the study was to assess the risk of occurrence of second cancers after prostate radiation therapy based on the analysis the literature, and to identify potential factors explaining the discrepancies in results between studies.

MATERIALS AND METHODS

A review of the literature was carried out, comparing the occurrence of second cancers in patients all presenting with prostate cancer, treated or not by radiation.

RESULTS

This review included 30 studies reporting the occurrence of second cancers in 2,112,000 patients treated or monitored for localized prostate cancer, including 1,111,000 by external radiation therapy and 103,000 by brachytherapy. Regarding external radiation therapy, the average follow-up was 7.3years. The majority of studies (80%) involving external radiation therapy, compared to no external radiation therapy, showed an increased risk of second cancers with a hazard ratio ranging from 1.13 to 4.9, depending on the duration of the follow-up. The median time to the occurrence of these second cancers after external radiotherapy ranged from 4 to 6years. An increased risk of second rectal and bladder cancer was observed in 52% and 85% of the studies, respectively. Considering a censoring period of more than 10 years after irradiation, 57% and 100% of the studies found an increased risk of rectal and bladder cancer, without any impact in overall survival. Studies of brachytherapy did not show an increased risk of second cancer. However, these comparative studies, most often old and retrospective, had many methodological biases.

CONCLUSION

Despite numerous methodological biases, prostate external radiation therapy appears associated with a moderate increase in the risk of second pelvic cancer, in particular bladder cancer, without impacting survival. Brachytherapy does not increase the risk of a second cancer.

Risk of Subsequent Neoplasms in Childhood Cancer Survivors After Radiation Therapy: A PENTEC Comprehensive Review

PURPOSE

A Pediatric Normal Tissue Effects in the Clinic (PENTEC) analysis of published investigations of central nervous system (CNS) subsequent neoplasms (SNs), subsequent sarcomas, and subsequent lung cancers in childhood cancer survivors who received radiation therapy (RT) was performed to estimate the effect of RT dose on the risk of SNs and the modification of this risk by host and treatment factors.

METHODS AND MATERIALS

A systematic literature review was performed to identify data published from 1975 to 2022 on SNs after prior RT in childhood cancer survivors. After abstract review, usable quantitative and qualitative data were extracted from 83 studies for CNS SNs, 118 for subsequent sarcomas, and 10 for lung SNs with 4 additional studies (3 for CNS SNs and 1 for lung SNs) later added. The incidences of SNs, RT dose, age, sex, primary cancer diagnosis, chemotherapy exposure, and latent time from primary diagnosis to SNs were extracted to assess the factors influencing risk for SNs. The excess relative ratio (ERR) for developing SNs as a function of dose was analyzed using inverse-variance weighted linear regression, and the ERR/Gy was estimated. Excess absolute risks were also calculated.

RESULTS

The ERR/Gy for subsequent meningiomas was estimated at 0.44 (95% CI, 0.19-0.68); for malignant CNS neoplasms, 0.15 (95% CI, 0.11-0.18); for sarcomas, 0.045 (95% CI, 0.023-0.067); and for lung cancer, 0.068 (95% CI, 0.03-0.11). Younger age at time of primary diagnosis was associated with higher risk of subsequent meningioma and sarcoma, whereas no significant effect was observed for age at exposure for risk of malignant CNS neoplasm, and insufficient data were available regarding age for lung cancer. Females had a higher risk of subsequent meningioma (odds ratio, 1.46; 95% CI, 1.22-1.76; P < .0001) relative to males, whereas no statistically significant sex difference was seen in risk of malignant CNS neoplasms, sarcoma SNs, or lung SNs. There was an association between chemotherapy receipt (specifically alkylating agents and anthracyclines) and subsequent sarcoma risk, whereas there was no clear association between specific chemotherapeutic agents and risk of CNS SNs and lung SNs.

CONCLUSIONS

This PENTEC systematic review shows a significant radiation dose-response relationship for CNS SNs, sarcomas, and lung SNs. Given the linear dose response, improved conformality around the target volume that limits the high dose volume might be a promising strategy for reducing the risk of SNs after RT. Other host- and treatment-related factors such as age and chemotherapy play a significant contributory role in the development of SNs and should be considered when estimating the risk of SNs after RT among childhood cancer survivors.

The Prevalence of Cancer in Dutch Female Patients with Idiopathic Scoliosis Compared with the General Population

Background and Objectives: Epidemiological studies have demonstrated the potential oncogenic effects of cumulative radiation exposure, particularly during childhood. One group experiencing repeated exposure to radiation at an early age for multiple years is patients treated for idiopathic scoliosis (IS). This study aimed to determine the relationship between childhood radiological exposure and adult cancer prevalence in children treated for IS. Materials and Methods: Data from 337 predominantly female patients treated at our hospital between January 1981 and January 1995 were gathered and compared to the Dutch national cancer rates. The standardized prevalence ratios for cancer in IS patients were compared with the cancer prevalence rates from the general Dutch population. Results: The overall cancer prevalence in women was 5.0%, with no significant difference compared to the general population (p = 0.425). The results of this study do not suggest that female patients treated for idiopathic scoliosis during childhood have an increased risk of cancer later in life. Conclusion: Despite being the largest recent study in its field, the modest participant number limits its ability to draw conclusions. However, the detailed data collected over a long observation period, alongside data from a period with comparable radiation rates, contributes to refining clinical practice and laying the groundwork for future systematic reviews.

The Natural History and Treatment of Meningiomas: An Update

Meningiomas are the most frequent nonmalignant tumors of the central nervous system (CNS). Despite their benign nature and slow-growing pattern, if not diagnosed early, these tumors may reach relatively large sizes causing significant morbidity and mortality. Some variants are located in hard-to-access locations, compressing critical neurovascular structures, and making the surgical management even more challenging. Although most meningiomas have a good long-term prognosis after treatment, there are still controversies over their management in a subset of cases. While surgery is the first-line treatment, the use of fractionated radiotherapy or stereotactic radiosurgery is indicated for residual or recurrent tumors, small lesions, and tumors in challenging locations. Advances in molecular genetics and ongoing clinical trial results have recently helped both to refine the diagnosis and provide hope for effective biomolecular target-based medications for treatment. This article reviews the natural history and current therapeutic options for CNS meningiomas.

Secondary Bladder Cancer After Prostate Cancer Treatment: An Age-matched Comparison Between Radiation and Surgery

BACKGROUND

Secondary malignancy is a long-term risk of radiation. External beam radiation therapy (EBRT) for prostate cancer treatment has been associated with later development of bladder cancer and worse bladder cancer features.

OBJECTIVE

We sought to provide an updated comparison of the long-term risk of bladder cancer after different localized prostate cancer treatments.

DESIGN, SETTING, AND PARTICIPANTS

Using the Surveillance, Epidemiology, and End Results (SEER) cancer registry, we compared an age-matched subset of patients who underwent radical prostatectomy (RP) with those who underwent EBRT, brachytherapy (BT), EBRT + BT, and RP followed by EBRT (RPtoEBRT) between 2000 and 2018. Our final cohort included 261 609 patients with a median follow-up of 11.6 yr.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Our primary outcomes were time to bladder cancer diagnosis, muscle-invasive bladder cancer diagnosis, and bladder cancer death. We used cause-specific hazard models considering death as a competing event. A similar analysis was performed on lung cancer, as a surrogate marker for smoking. We also compared proportions of variant histology, high-grade, and invasive disease among bladder cancers that occurred after radiation versus RP using chi-square testing.

RESULTS AND LIMITATIONS

All radiation groups were associated with bladder cancer diagnosis; hazard ratios (HRs) were 1.72, 1.85, 1.80, and 1.53 for EBRT, BT, EBRT + BT, and RPtoEBRT, respectively, using RP as a referent (all p < 0.001). HRs for bladder cancer death were even higher: 2.39, 2.57, and 3.02 for EBRT, BT, and EBRT + BT, respectively (all p < 0.001), except for RPtoEBRT (HR 1.43, p = 0.28). Lung cancer diagnosis was also associated with radiation but at lower HRs-1.63, 1.32, 1.42, and 1.30 for EBRT, BT, EBRT + BT, and RPtoEBRT, respectively (all p < 0.001). There were a higher proportion of ≥T2, ≥T3, and sarcomatoid variant bladder cancers after radiation (all p < 0.01) CONCLUSIONS: The risk of developing and dying from bladder cancer is increased in patients treated with radiation compared with those treated with RP. The risk was similar for BT and EBRT. Bladder cancers after radiation are more likely to be sarcomatoid variant and present as muscle invasive.

PATIENT SUMMARY

We observed the rates of bladder cancer after patients had undergone surgery or radiation for prostate cancer, and found higher rates of bladder cancer after radiation. We also observed that bladder cancers that occur after radiation tend to be more aggressive.

Patient shielding during dentomaxillofacial radiography: Recommendations from the American Academy of Oral and Maxillofacial Radiology

BACKGROUND

The American Academy of Oral and Maxillofacial Radiology established an ad hoc committee to draft evidence-based recommendations and clinical guidance for the application of patient contact shielding during dentomaxillofacial imaging.

TYPES OF STUDIES REVIEWED

The committee reviewed monographs and reports from radiation protection organizations and studies that reported radiation dose to gonads, breasts, and thyroid gland from dentomaxillofacial imaging.

RESULTS

Considering the absence of radiation-induced heritable effects in humans and the negligible dose to the gonads and fetus from dentomaxillofacial imaging, the committee recommends discontinuing shielding of the gonads, pelvic structures, and fetuses during all dentomaxillofacial radiographic imaging procedures. On the basis of radiation doses from contemporaneous maxillofacial imaging, the committee considered that the risks from thyroid cancer are negligible and recommends that thyroid shielding not be used during intraoral, panoramic, cephalometric, and cone-beam computed tomographic imaging.

PRACTICAL IMPLICATIONS

This position statement informs and educates the reader on evolving radiation protection practices and provides simple, unequivocal guidance to dental personnel to implement these guidelines. State and local authorities should be contacted to update regulations to reflect these recommendations.

Immediate effects of acute Mars mission equivalent doses of SEP and GCR radiation on the murine gastrointestinal system-protective effects of curcumin-loaded nanolipoprotein particles (cNLPs)

Introduction

Missions beyond low Earth orbit (LEO) will expose astronauts to ionizing radiation (IR) in the form of solar energetic particles (SEP) and galactic cosmic rays (GCR) including high atomic number and energy (HZE) nuclei. The gastrointestinal (GI) system is documented to be highly radiosensitive with even relatively low dose IR exposures capable of inducing mucosal lesions and disrupting epithelial barrier function. IR is also an established risk factor for colorectal cancer (CRC) with several studies examining long-term GI effects of SEP/GCR exposure using tumor-prone APC mouse models. Studies of acute short-term effects of modeled space radiation exposures in wildtype mouse models are more limited and necessary to better define charged particle-induced GI pathologies and test novel medical countermeasures (MCMs) to promote astronaut safety.

Methods

In this study, we performed ground-based studies where male and female C57BL/6J mice were exposed to γ-rays, 50 MeV protons, or 1 GeV/n Fe-56 ions at the NASA Space Radiation Laboratory (NSRL) with histology and immunohistochemistry endpoints measured in the first 24 h post-irradiation to define immediate SEP/GCR-induced GI alterations.

Results

Our data show that unlike matched γ-ray controls, acute exposures to protons and iron ions disrupts intestinal function and induces mucosal lesions, vascular congestion, epithelial barrier breakdown, and marked enlargement of mucosa-associated lymphoid tissue. We also measured kinetics of DNA double-strand break (DSB) repair using gamma-H2AX- specific antibodies and apoptosis via TUNEL labeling, noting the induction and disappearance of extranuclear cytoplasmic DNA marked by gamma-H2AX only in the charged particle-irradiated samples. We show that 18 h pre-treatment with curcumin-loaded nanolipoprotein particles (cNLPs) delivered via IV injection reduces DSB-associated foci levels and apoptosis and restore crypt villi lengths.

Discussion

These data improve our understanding of physiological alterations in the GI tract immediately following exposures to modeled space radiations and demonstrates effectiveness of a promising space radiation MCM.

Comparison of Proportional Mortality Between Korean Atomic Bomb Survivors and the General Population During 1992-2019

BACKGROUND

Atomic bombs dropped on Hiroshima and Nagasaki in Japan in August 1945 were estimated to have killed approximately 70,000 Koreans. In Japan, studies on the health status and mortality of atomic bomb survivors compared with the non-exposed population have been conducted. However, there have been no studies related to the mortality of Korean atomic bomb survivors. Therefore, we aimed to study the cause of death of atomic bomb survivors compared to that of the general population.

METHODS

Of 2,299 atomic bomb survivors registered with the Korean Red Cross, 2,176 were included in the study. In the general population, the number of deaths by age group was calculated from 1992 to 2019, and 6,377,781 individuals were assessed. Causes of death were categorized according to the Korean Standard Classification of Diseases. To compare the proportional mortality between the two groups, the P value for the ratio test was confirmed, and the Cochran-Armitage trend test and χ² test were performed to determine the cause of death according to the distance from the hypocenter.

RESULTS

Diseases of the circulatory system were the most common cause of death (25.4%), followed by neoplasms (25.1%) and diseases of the respiratory system (10.6%) in atomic bomb survivors who died between 1992 and 2019. The proportional mortality associated with respiratory diseases, nervous system diseases, and other diseases among atomic bomb survivors was higher than that of the general population. Of the dead people between 1992 and 2019, the age at death of survivors who were exposed at a close distance was younger than those who were exposed at a greater distance.

CONCLUSION

Overall, proportional mortality of respiratory diseases and nervous system diseases was high in atomic bomb survivors, compared with the general population. Further studies on the health status of Korean atomic bomb survivors are needed.

Insights into radiation carcinogenesis based on dose-rate effects in tissue stem cells

PURPOSE

Increasing epidemiological and biological evidence suggests that radiation exposure enhances cancer risk in a dose-dependent manner. This can be attributed to the 'dose-rate effect,' where the biological effect of low dose-rate radiation is lower than that of the same dose at a high dose-rate. This effect has been reported in epidemiological studies and experimental biology, although the underlying biological mechanisms are not completely understood. In this review, we aim to propose a suitable model for radiation carcinogenesis based on the dose-rate effect in tissue stem cells.

METHODS

We surveyed and summarized the latest studies on the mechanisms of carcinogenesis. Next, we summarized the radiosensitivity of intestinal stem cells and the role of dose-rate in the modulation of stem-cell dynamics after irradiation.

RESULTS

Consistently, driver mutations can be detected in most cancers from past to present, supporting the hypothesis that cancer progression is initiated by the accumulation of driver mutations. Recent reports demonstrated that driver mutations can be observed even in normal tissues, which suggests that the accumulation of mutations is a necessary condition for cancer progression. In addition, driver mutations in tissue stem cells can cause tumors, whereas they are not sufficient when they occur in non-stem cells. For non-stem cells, tissue remodeling induced by marked inflammation after the loss of tissue cells is important in addition to the accumulation of mutations. Therefore, the mechanism of carcinogenesis differs according to the cell type and magnitude of stress. In addition, our results indicated that non-irradiated stem cells tend to be eliminated from three-dimensional cultures of intestinal stem cells (organoids) composed of irradiated and non-irradiated stem cells, supporting the stem-cell competition.

CONCLUSIONS

We propose a unique scheme in which the dose-rate dependent response of intestinal stem cells incorporates the concept of the threshold of stem-cell competition and context-dependent target shift from stem cells to whole tissue. The concept highlights four key issues that should be considered in radiation carcinogenesis: i.e. accumulation of mutations; tissue reconstitution; stem-cell competition; and environmental factors like epigenetic modifications.

Mitochondrial Signaling Pathways Associated with DNA Damage Responses

Under physiological and stress conditions, mitochondria act as a signaling platform to initiate biological events, establishing communication from the mitochondria to the rest of the cell. Mitochondrial adenosine triphosphate (ATP), reactive oxygen species, cytochrome C, and damage-associated molecular patterns act as messengers in metabolism, oxidative stress response, bystander response, apoptosis, cellular senescence, and inflammation response. In this review paper, the mitochondrial signaling in response to DNA damage was summarized. Mitochondrial clearance via fusion, fission, and mitophagy regulates mitochondrial quality control under oxidative stress conditions. On the other hand, damaged mitochondria release their contents into the cytoplasm and then mediate various signaling pathways. The role of mitochondrial dysfunction in radiation carcinogenesis was discussed, and the recent findings on radiation-induced mitochondrial signaling and radioprotective agents that targeted mitochondria were presented. The analysis of the mitochondrial radiation effect, as hypothesized, is critical in assessing radiation risks to human health.

Low-Dose Extrapolation Factors Implied by Mortality and Incidence Data from the Japanese Atomic Bomb Survivor Life Span Study Data

Assessment of the effect of low dose and low-dose-rate exposure depends critically on extrapolation from groups exposed at high dose and high-dose rates such as the Japanese atomic bomb survivor data, and has often been achieved via application of a dose and dose-rate effectiveness factor (DDREF). An important component of DDREF is the factor determining the effect of extrapolation of dose, the so-called low-dose extrapolation factor (LDEF). To assess LDEF models linear (or linear quadratic) in dose are often fitted. In this report LDEF is assessed via fitting relative rate models that are linear or linear quadratic in dose to the latest Japanese atomic bomb survivor data on solid cancer, leukemia and circulatory disease mortality (followed from 1950 through 2003) and to data on solid cancer, lung cancer and urinary tract cancer incidence. The uncertainties in LDEF are assessed using parametric bootstrap techniques. Analysis is restricted to survivors with <3 Gy dose. There is modest evidence for upward curvature in dose response in the mortality data. For leukemia and for all solid cancer excluding lung, stomach and breast cancer there is significant curvature (P < 0.05). There is no evidence of curvature for circulatory disease (P > 0.5). The estimate of LDEF for all solid cancer mortality is 1.273 [95% confidence intervals (CI) 0.913, 2.182], for all solid cancer mortality excluding lung cancer, stomach cancer and breast cancer is 2.183 (95% CI 1.090, >100) and for leukemia mortality is 11.447 (95% CI 2.390, >100). For stomach cancer mortality LDEF is modestly raised, 1.077 (95% CI 0.526, >100), while for lung cancer, female breast cancer and circulatory disease mortality the LDEF does not much exceed 1. LDEF for solid cancer incidence is 1.186 (95% CI 0.942, 1.626) and for urinary tract cancer is 1.298 (95% CI <0, 7.723), although for lung cancer LDEF is not elevated, 0.842 (95% CI 0.344, >100).

Considerations for carcinogenesis countermeasure development using mouse models

Activities in space will expose humans to profoundly new environments, challenging human performance and will require innovative supportive technologies. Among these environmental variables, exposure to ionizing radiation is a major concern for astronauts, as the long-term effects of exposure on diverse tissues are poorly understood. This need however creates opportunities for novel approaches, particularly in the development of countermeasures against the effects of ionizing radiation exposure. Carcinogenesis presents a unique challenge as a disease process, due to the inherent complexities of the process and the challenges of obtaining a large volume of clinical evidence. Thus, developing the countermeasures to address potential effects of ionizing radiation exposure will require understanding biological underpinnings to design countermeasures effectively in conjunction with highly robust modeling approaches to test and examine in vivo. This review will highlight specific considerations for accelerated development of space radiation countermeasures against carcinogenesis.

The Armed Conflict and the Impact on Patients With Cancer in Ukraine: Urgent Considerations

On February 24, 2022, a war began within the Ukrainian borders. At least 3.0 million Ukrainian inhabitants have already fled the country. Critical infrastructure, including hospitals, has been damaged. Children with cancer were urgently transported to foreign countries, in an effort to minimize interruption of their life-saving treatments. Most adults did not have that option. War breeds cancer—delaying diagnosis, preventing treatment, and increasing risk. We project that a modest delay in care of only 4 months for five prevalent types of cancer will lead to an excess of over 3,600 cancer deaths in the subsequent years. It is critical that we establish plans to mitigate that risk as soon as possible.

Ukraine conflict may cost 3600 lives or more because of a delay and lack of access for patients with cancer.

Comparison of All Solid Cancer Mortality and Incidence Dose-Response in the Life Span Study of Atomic Bomb Survivors, 1958-2009

Recent analysis of all solid cancer incidence (1958-2009) in the Life Span Study (LSS) revealed evidence of upward curvature in the radiation dose response among males but not females. Upward curvature in sex-averaged excess relative risk (ERR) for all solid cancer mortality (1950-2003) was also observed in the 0-2 Gy dose range. As reasons for non-linearity in the LSS are not completely understood, we conducted dose-response analyses for all solid cancer mortality and incidence applying similar methods [1958-2009 follow-up, DS02R1 doses, including subjects not-in-city (NIC) at the time of the bombing] and statistical models. Incident cancers were ascertained from Hiroshima and Nagasaki cancer registries, while cause of death was ascertained from death certificates throughout Japan. The study included 105,444 LSS subjects who were alive and not known to have cancer before January 1, 1958 (80,205 with dose estimates and 25,239 NIC subjects). Between 1958 and 2009, there were 3.1 million person-years (PY) and 22,538 solid cancers for incidence analysis and 3.8 million PY and 15,419 solid cancer deaths for mortality analysis. We fitted sex-specific ERR models adjusted for smoking to both types of data. Over the entire range of doses, solid cancer mortality dose-response exhibited a borderline significant upward curvature among males (P = 0.062) and significant upward curvature among females (P = 0.010); for solid cancer incidence, as before, we found a significant upward curvature among males (P = 0.001) but not among females (P = 0.624). The sex difference in magnitude of dose-response curvature was statistically significant for cancer incidence (P = 0.017) but not for cancer mortality (P = 0.781). The results of analyses in the 0-2 Gy range and restricted lower dose ranges generally supported inferences made about the sex-specific dose-response shape over the entire range of doses for each outcome. Patterns of sex-specific curvature by calendar period (1958-1987 vs. 1988-2009) and age at exposure (0-19 vs. 20-83) varied between mortality and incidence data, particularly among females, although for each outcome there was an indication of curvature among 0-19-year-old male survivors in both calendar periods and among 0-19-year-old female survivors in the recent period. Collectively, our findings indicate that the upward curvature in all solid cancer dose response in the LSS is neither specific to males nor to incidence data; its evidence appears to depend on the composition of sites comprising all solid cancer group and age at exposure or time. Further follow up and site-specific analyses of cancer mortality and incidence will be important to confirm the emerging trend in dose-response curvature among young survivors and unveil the contributing factors and sites.

Modulation of Secondary Cancer Risks from Radiation Exposure by Sex, Age and Gonadal Hormone Status: Progress, Opportunities and Challenges

Available data on cancer secondary to ionizing radiation consistently show an excess (2-fold amount) of radiation-attributable solid tumors in women relative to men. This excess risk varies by organ and age, with the largest sex differences (6- to more than 10-fold) found in female thyroid and breasts exposed between birth until menopause (~50 years old) relative to age-matched males. Studies in humans and animals also show large changes in cell proliferation rates, radiotracer accumulation and target density in female reproductive organs, breast, thyroid and brain in conjunction with physiological changes in gonadal hormones during the menstrual cycle, puberty, lactation and menopause. These sex differences and hormonal effects present challenges as well as opportunities to personalize radiation-based treatment and diagnostic paradigms so as to optimize the risk/benefit ratios in radiation-based cancer therapy and diagnosis. Specifically, Targeted Radionuclide Therapy (TRT) is a fast-expanding cancer treatment modality utilizing radiopharmaceuticals with high avidity to specific molecular tumor markers, many of which are influenced by sex and gonadal hormone status. However, past and present dosimetry studies of TRT agents do not stratify results by sex and hormonal environment. We conclude that cancer management using ionizing radiation should be personalized and informed by the patient sex, age and hormonal status.

Ionizing radiation and cancer: The failure of the risk model

This review presents evidence that the methodology that supports the current radiation risk model for cancer is insecure. As a consequence, the legal limits on internal exposures to certain common radionuclides are incorrect by several orders of magnitude. Because of this, hundreds of millions of people will have developed cancer due to internal exposures from atmospheric testing fallout, nuclear accidents, Depleted Uranium and releases from nuclear sites. There are fatal errors in both the mechanistic and epidemiological bases of the Linear No Threshold (LNT) Absorbed Dose model. The review discusses the history of the model and refers to published studies that clearly demonstrate these errors. It argues that the ways in which the models were constructed were arbitrary, capricious and unscientific.

Risk factors for second primary malignancies following thyroid cancer: a nationwide cohort study

OBJECTIVE

Thyroid cancer survivors have a high risk of second primary malignancies (SPMs). We aimed to evaluate the site-specific incidence, prognosis, and risk factors for metachronous SPMs following thyroid cancer.

DESIGN

A nationwide cohort study.

METHODS

This study included data from the Korea National Health Insurance Service (between 2002 and 2018). Exposure to diagnostic radiation was defined by the number of computed tomography (CT) and positron emission tomography-CT scans after the index date. A cumulative radioactive iodine (RAI) dose >100 mCi was considered high-dose RAI.

RESULTS

During the median 6 years of follow-up, among 291 640 patients, 13 083 (4.5%) developed SPMs. Thyroid cancer survivors had a 26% increased risk of SPMs compared with the general population (standardized incidence ratio: 1.26; 95% CI: 1.22-1.29). Furthermore, those with SPMs had a significantly poorer survival rate than those without SPMs (hazard ratio: 11.85; 95% CI: 11.21-12.54; P < 0.001). Significantly elevated risks were observed in myeloid leukemia and 13 solid cancer sites: lip, salivary gland, small intestine, larynx, lung, mediastinum and pleura, mesothelium, breast, corpus uteri, ovary, prostate, kidney, and bladder. Frequent diagnostic medical radiation exposure and high-dose RAI therapy were independent risk factors for several SPMs, including the cancer of salivary gland, lung, mediastinum and pleura, breast, kidney, and bladder, as well as myeloid leukemia.

CONCLUSIONS

Frequent diagnostic radiation exposure and high-dose RAI therapy are independent risk factors for SPM following thyroid cancer. Clinicians need to consider minimizing unnecessary diagnostic radiation exposure and administering a high dose RAI only when justified in patients with thyroid cancer.

Radiation cancer risk at different dose rates: new dose-rate effectiveness factors derived from revised A-bomb radiation dosimetry data and non-tumor doses

The dose rate of atomic bomb (A-bomb) radiation to the survivors has still remained unclear, although the dose-response data of A-bomb cancers has been taken as a standard in estimating the cancer risk of radiation and the dose and dose-rate effectiveness factor (DDREF). Since the applicability of the currently used DDREF of 2 derived from A-bomb data is limited in a narrow dose-rate range, 0.25-75 Gy/min as estimated from analysis of DS86 dosimetry data in the present study, a non-tumor dose (Dnt) was applied in an attempt to gain a more universal dose-rate effectiveness factor (DREF), where Dnt is an empirical parameter defined as the highest dose at which no statistically significant tumor increase is observed above the control level and its magnitude depends on the dose rate. The new DREF values were expressed as a function of the dose rate at four exposure categories, i.e. partial body low LET, whole body low linear energy transfer (LET), partial body high LET and whole body high LET and provided a value of 14 for environmental level radiation at a dose rate of 10-9 Gy/min for whole body low LET.

Intensity Modulated Proton Therapy Better Spares Non-Adjacent Organs and Reduces the Risk of Secondary Malignant Neoplasms in the Treatment of Sinonasal Cancers

This study compare dosimetric parameters and secondary malignancy risk (SMN) using intensity modulated proton therapy (IMPT) and volumetric modulated arc therapy (VMAT) plans for the treatment of sinonasal cancer (SC). After IRB-approval, 10 patients previously treated with IMPT for cancers of the ethmoid, sphenoid, maxillary, or frontal sinuses were identified. Dosimetrists blinded to the IMPT plans generated VMAT plans for comparison. Volume coverage and dose to organs at risk (OAR) were recorded and compared. Organ equivalent dose (OED) of tissues outside of the treatment volume was used to define the excess absolute and relative risk of SMNs. In all cases, both VMAT and IMPT provided acceptable target volume coverage and were able to meet OAR constraints. IMPT was superior for brain V10, V30, and mean, brainstem D0.01 ipsilateral cochlea V30, contralateral cochlea mean, contralateral lacrimal gland mean, contralateral parotid mean, spinal cord D0.01 and body outside of the CTV V10, V20, and V30. VMAT was superior for ipsilateral eye mean, ipsilateral lens mean, CTV V100 and maximum hotspot. The relative risk of SMNs with VMAT compared to IMPT is 3.35 (95% CI, 1.92-5.89). For the treatment of SC, IMPT spares OARs that are not immediately adjacent to the treatment volume and reduces the risk of SMNs when compared to VMAT. VMAT spares OARs abutting the target volume better than IMPT and has more homogenous target coverage. Tumors of the ethmoid sinus, benefit more from IMPT, while tumors located elsewhere require application of our findings on a case by case basis.

Identification of Genetic Predispositions Related to Ionizing Radiation in Primary Human Skin Fibroblasts From Survivors of Childhood and Second Primary Cancer as Well as Cancer-Free Controls: Protocol for the Nested Case-Control Study KiKme

BACKGROUND

Therapy for a first primary neoplasm (FPN) in childhood with high doses of ionizing radiation is an established risk factor for second primary neoplasms (SPN). An association between exposure to low doses and childhood cancer is also suggested; however, results are inconsistent. As only subgroups of children with FPNs develop SPNs, an interaction between radiation, genetic, and other risk factors is presumed to influence cancer development.

OBJECTIVE

Therefore, the population-based, nested case-control study KiKme aims to identify differences in genetic predisposition and radiation response between childhood cancer survivors with and without SPNs as well as cancer-free controls.

METHODS

We conducted a population-based, nested case-control study KiKme. Besides questionnaire information, skin biopsies and saliva samples are available. By measuring individual reactions to different exposures to radiation (eg, 0.05 and 2 Gray) in normal somatic cells of the same person, our design enables us to create several exposure scenarios for the same person simultaneously and measure several different molecular markers (eg, DNA, messenger RNA, long noncoding RNA, copy number variation).

RESULTS

Since 2013, 101 of 247 invited SPN patients, 340 of 1729 invited FPN patients, and 150 of 246 invited cancer-free controls were recruited and matched by age and sex. Childhood cancer patients were additionally matched by tumor morphology, year of diagnosis, and age at diagnosis. Participants reported on lifestyle, socioeconomical, and anthropometric factors, as well as on medical radiation history, health, and family history of diseases (n=556). Primary human fibroblasts from skin biopsies of the participants were cultivated (n=499) and cryopreserved (n=3886). DNA was extracted from fibroblasts (n=488) and saliva (n=510).

CONCLUSIONS

This molecular-epidemiological study is the first to combine observational epidemiological research with standardized experimental components in primary human skin fibroblasts to identify genetic predispositions related to ionizing radiation in childhood and SPNs. In the future, fibroblasts of the participants will be used for standardized irradiation experiments, which will inform analysis of the case-control study and vice versa. Differences between participants will be identified using several molecular markers. With its innovative combination of experimental and observational components, this new study will provide valuable data to forward research on radiation-related risk factors in childhood cancer and SPNs.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/32395.

Translocation dose-response curve for 137Cs γ-rays: Dose validation at various dose rate and changing dose rate conditions

A Fluorescence In-Situ Hybridization (FISH) based translocation dose-response curve has been constructed for biodosimetry application in our nuclear establishment at Kalpakkam, India. Peripheral blood sample from a healthy male donor (27 years) was exposed to nine different doses (0.1 Gy-5 Gy) of ¹³⁷Cs γ-rays (100 mGy/min) in an automated calibration facility with a linear distancing system and subjected to FISH assay using chromosome 1, 2 and 4 specific fluorescent probes. Validation of the dose-response curve was done following three different approaches i) by blind test method ii) using blood samples exposed to γ doses (0.5, 1 & 2 Gy) at different dose rates (124, 23 & 10 mGy/min) and iii) with blood samples exposed to 0.5, 1 & 2 Gy γ doses at changing dose rates (increasing and decreasing dose rates). Results showed that a predefined dose-response curve constructed at a particular acute dose rate can be used for dose estimation in exposures involving varying dose rates and changing dose rate scenarios.

Modeling Radiation-Induced Neoplastic Cell Transformation In Vitro and Tumor Induction In Vivo with the Local Effect Model

Ionizing radiation induces DNA damage to cycling cells which, if left unrepaired or misrepaired, can cause cell inactivation or heritable, viable mutations. The latter can lead to cell transformation, which is thought to be an initial step of cancer formation. Consequently, the study of radiation-induced cell transformation promises to offer insights into the general properties of radiation carcinogenesis. As for other end points, the effectiveness in inducing cell transformation is elevated for radiation qualities with high linear energy transfer (LET), and the same is true for cancer induction. In considering DNA damage as a common cause of both cell death and transformations, a worthwhile approach is to apply mathematical models for the relative biological effectiveness (RBE) of cell killing to also assess the carcinogenic potential of high-LET radiation. In this work we used an established RBE model for cell survival and clinical end points, the local effect model (LEM), to estimate the transformation probability and the carcinogenic potential of ion radiation. The provided method consists of accounting for the competing processes of cell inactivation and induction of transformations or carcinogenic events after radiation exposure by a dual use of the LEM. Correlations between both processes inferred by the number of particle impacts to individual cells were considered by summing over the distribution of hits that individual cells receive. RBE values for cell transformation in vitro were simulated for three independent data sets, which were also used to gauge the approach. The simulations reflect the general RBE systematics both in magnitude and in energy and LET dependence. To challenge the developed method, in vivo carcinogenesis was investigated using the same concepts, where the probability for cancer induction within an irradiated organ was derived from the probability of finding carcinogenic events in individual cells. The predictions were compared with experimental data of carcinogenesis in Harderian glands of mice. Again, the developed method shows the same characteristics as the experimental data. We conclude that the presented method is helpful to predictively assess RBE for both neoplastic cell transformation and tumor induction after ion exposure within a wide range of LET values. The theoretical concept requires a non-linear component in the photon dose response for carcinogenic end points as a precondition for the observed enhanced effects after ion exposure, thus contributing to a long debate in epidemiology. Future work will use the method for assessing cancer induction in radiation therapy and exposure scenarios frequently discussed in radiation protection.

Total body irradiation as part of conditioning regimens in childhood leukemia-long-term outcome, toxicity, and secondary malignancies

Background

Total body irradiation (TBI) is an established part of conditioning regimens prior to stem cell transplantation in childhood leukemia but is associated with long-term toxicity. We retrospectively analyzed survival, long-term toxicity, and secondary malignancies in a pooled cohort of pediatric patients (pts.) treated with the same TBI regimen.

Methods

Analyzed were 109 pts. treated between September 1996 and November 2015. Conditioning treatment according to EBMT guidelines and the ALL SCTped 2012 FORUM trial consisted of chemotherapy (CT) and TBI with 2 Gy b.i.d. on 3 consecutive days to a total dose of 12 Gy. Median follow-up was 97.9 months (2–228 months).

Results

Overall survival (OS) in our cohort at 2, 5, and 10 years was 86.1, 75.5, and 63.0%, respectively. Median survival was not reached. Long-term toxicity developed in 47 pts. After chronically abnormal liver and kidney parameters in 31 and 7 pts., respectively, growth retardation was the most frequent finding as seen in 13 pts. Secondary malignancies were rare (n = 3).

Conclusion

TBI-containing conditioning regimens in pediatric stem cell transplantation (SCT) are highly effective. Efforts to replace TBI- with CT-containing regimens have only been successful in subgroups of pts. Although we could show long-term toxicity in 43% of pts., overall survival was 63% at 10 years. Still, long-term effects such as growth retardation can permanently impact the pts.’ quality of life and functioning. Along with new substances, efforts should be undertaken to optimize TBI techniques and accompany the treatment by systematic follow-up programs beyond 5 years to improve detection of rare events.

Increasing incidence and survival of paediatric and adolescent thyroid cancer in Cyprus 1998-2017: A population-based study from the Cyprus Pediatric Oncology Registry

BACKGROUND

Paediatric and adolescent thyroid cancer incidence rates are increasing in many countries. We determined incidence rates, temporal trends and survival from thyroid cancer diagnosed in childhood and adolescence in Cyprus during 1998-2017.

METHODS

Patients aged 0-19 years, diagnosed with thyroid cancer in the Pediatric Oncology Registry of Cyprus were included. Crude incidence rates, age standardized rates, time trends and overall survival were analysed. Annual rates and temporal trends were calculated using Microsoft Excel 2016 and Joinpoint regression analysis.

RESULTS

Eighty-one cases (76.5 % female, 23.5 % male) were identified. The crude rates (per 100,000 persons) were for both sexes 2.00 (95 % CI 1.61, 2.49), females 3.15 (95 % CI 2.45, 4.03) and males 0.92 (95 % CI 0.58, 1.44). The annual percentage changes of crude and standardised rates were 7.5 % (p < 0.05) and 7.6 % (p < 0.05). The annual percentage changes of crude rates were for females 5.1 % (p = 0.1), males 8.4 % (p < 0.05) and 15-19-year-olds 7.6 % (p < 0.05). The female to male rate ratio was 3.42 (95 % CI 2.06, 5.74). Papillary thyroid carcinoma represented 86.4 % of all cases. There was only one case after previous cancer therapy. The rate ratio of 2nd (2008-2017) to 1st (1998-2007) periods for metastatic (regional) stages was 3.76 (95 % CI 1.74, 8.31). Survival until 2018 was 100 %.

CONCLUSION

This population-based study demonstrated that thyroid cancer incidence rates in 0-19-year-olds in Cyprus was among the world's highest. Increasing trends mainly affected males and females aged 15-19 years with papillary thyroid carcinoma, the dominant type. Cases after previous cancer therapy didn't contribute to increasing rates. The increase of metastatic cases suggests a true increase of thyroid cancer rather than overdiagnosis. Although prognosis is excellent with 100 % survival, the rising incidence rate is unexplained, indicating the need to identify causes.

Immunohistochemical Analysis of Toll-Like Receptors, MyD88, and TRIF in Human Papillary Thyroid Carcinoma and Anaplastic Thyroid Carcinoma

Purpose

We hypothesized that innate immune response pathways might be involved in thyroid carcinogenesis. To investigate this hypothesis, we aimed at analyzing the expression of several receptors and molecules in the innate immune system in papillary thyroid carcinoma (PTC) and anaplastic thyroid carcinoma (ATC) tissues.

Methods

Of the surgically resected specimens, 11 ATC tissues, 25 PTC tissues, and 8 nodular hyperplasia (NH) tissues were selected and examined for the expression of toll-like receptor (TLR) 2, TLR3, TLR4, TLR5, TLR7, TLR9, the myeloid differentiation primary response gene 88 (MyD88), and toll-interleukin-1 receptor domain-containing adaptor inducing INF-β (TRIF) by immunohistochemistry (IHC).

Results

Several TLRs were expressed in each tissue. TLR3 was strongly expressed in all tissues. In contrast, TLR4 was not detected in any tissues. While TLR5 was moderately expressed in NH but significantly reduced in PTC and ATC, TLR9 was absent in NH tissue but moderately expressed in both PTC and ATC. On MyD88 expression, no significant difference was found between PTC and ATC. TRIF was significantly upregulated in PTC and ATC compared to NH. Surprisingly, PTC and ATC tissues exhibited similar expression patterns of TLRs, MyD88, and TRIF.

Conclusion

These data suggest the involvement of the innate immune system in both PTC and ATC. Specifically, TLR3-mediated TRIF activation was confirmed in PTC and ATC. This provides new insight into thyroid carcinogenesis.

Risk perception of the pre-distribution of stable iodine to guardians of children living around the Genkai Nuclear Power Plant, Saga Prefecture, Japan

Iodine thyroid blocking (ITB) is effective for preventing childhood thyroid cancer when radioactive iodine is released into the environment during a nuclear power plant accident. Japan employs the pre-distribution of stable iodine (PDSI) to residents living near nuclear power plants; however, the number of residents who have actually received stable iodine to date remains limited. The aim of this study was to evaluate the profile of guardians of children living around the Genkai Nuclear Power Plant (GNPP) in Japan. We distributed self-administered questionnaires regarding perception of risks associated with administration of stable iodide to approximated 400 guardians of children aged 0-6 in 10 kindergartens located in four municipalities. We obtained responses from 286 guardians, and after excluding invalid responses, 247 were included in the analysis. Logistic regression analysis revealed that living within 5 km of the GNPP (odds ratio [OR] = 4.48, 95% confidence interval [CI]: 2.43-8.24), awareness of preferential implementation of ITB to children (OR = 3.33, 95%CI: 1.78-6.22), and awareness of the prophylaxis booklet published by the local government (OR = 2.53, 95%CI: 1.37-4.68) were independently associated with PDSI for children. The main reasons for not receiving PDSI were "anxiety about the side effects of stable iodine" (40.2%), "distrust of the effectiveness of SI" (23.5%), "complicated procedures for receiving stable iodine" (15.7%) and "missed the date for receiving stable iodine" (8.8%). In the case of ITB implementation during a nuclear emergency, it is necessary to clarify the risk perceptions of guardians and adapt risk communication accordingly.

Radiation Risks for the Incidence of Kidney, Bladder and Other Urinary Tract Cancers: 1958-2009

As part of the recent series of articles to create a comprehensive description of the radiation risks of solid cancer incidence after ionizing radiation exposure, based on the atomic bomb survivors' Life Span Study (LSS), this work focuses on the risks of urinary tract cancer (UTC) and kidney cancer. Analyses covered a 52-year period of follow-up, through 2009, among 105,444 eligible survivors who were alive and cancer free in 1958. This represents an additional 11 years of follow-up since the last comprehensive report, with a total of 3,079,502 person-years. We observed 790 UTC and 218 kidney cancer cases. Adjusted for smoking, there was a strong linear radiation dose response for UTC. The sex-averaged excess relative risk per 1 Gy (ERR/Gy) was 1.4 (95% confidence interval, CI: 0.82 to 2.1). Both males and females showed significantly increased ERRs/Gy with female point estimates at a factor of 3.4 (95% CI: 1.4 to 8.6) greater than male estimates. UTC radiation risks were largely unmodified by age at exposure or attained age. The attributable fraction of UTC to radiation exposure was approximately 18% while that attributed to smoking was 48%. Kidney cancer showed an increased ERR due to smoking (0.56 per 50 pack-years; 95% CI -0.007 to 1.6; P = 0.054), but we did not observe any strong associations of kidney cancer with radiation exposure, although sex-specific dose responses were found to be statistically different.

Radiation Risk of Ovarian Cancer in Atomic Bomb Survivors: 1958-2009

There is limited evidence concerning the association between radiation exposure and ovarian cancer. We evaluated radiation risk of ovarian cancer between 1958 and 2009 among 62,534 female atomic bomb survivors in the Life Span Study cohort, adding 11 years of follow-up from the previously reported study. Poisson regression methods were used to estimate excess relative risk per Gy (ERR/Gy) for total ovarian cancer and according to tumor type. We assessed the modifying effect of follow-up period and other factors on the radiation risk. We ascertained 288 first primary ovarian cancers including 77 type 1 epithelial cancers, 75 type 2 epithelial cancers, 66 epithelial cancers of undetermined type and 70 other cancers. Radiation dose was positively, although not significantly, associated with risk of total ovarian cancer [ERR/Gy = 0.30, 95% confidence interval (CI): -0.22 to 1.11]. There was a suggestion of heterogeneity in radiation effects (P = 0.08) for type 1 (ERR/Gy = -0.32, 95% CI: <-0.32 to 0.88) and type 2 cancers (ERR/Gy = 1.24, 95% CI: -0.08 to 4.16). There were no significant trends in the ERR with time since exposure or age at exposure. Further follow-up will help characterize more accurately the patterns of radiation risk for total ovarian cancer and its types.

Risk of Prostate Cancer Incidence among Atomic Bomb Survivors: 1958-2009

Epidemiological evidence for a radiation effect on prostate cancer risk has been inconsistent and largely indicative of no or little effect. Here we studied prostate cancer incidence among males of the Life Span Study cohort of atomic bomb survivors in a follow-up from 1958 to 2009, eleven years more than was previously reported. During this period there were 851 incident cases of prostate cancer among 41,544 male subjects, doubling the total number of cases in the cohort. More than 50% of the cases were diagnosed among those who were less than 20 years of age at the time of the bombings and who were at, or near, the ages of heightened prostate cancer risks during the last decade of follow-up. In analyses of the radiation dose response using Poisson regression methods, we used a baseline-rate model that allowed for calendar period effects corresponding to the emergence of prostate-specific antigen screening in the general population as well as effects of attained age and birth cohort. The model also allowed for markedly increased baseline rates among the Adult Health Study participants between 2005 and 2009, a period during which a prostate-specific antigen test was included in Adult Health Study biennial health examinations. We found a significant linear dose response with an estimated excess relative risk (ERR) per Gy of 0.57 (95% CI: 0.21, 1.00, P = 0.001). An estimated 40 of the observed cases were attributed to radiation exposure from the bombings. There was a suggestion of the ERR decreasing with increasing age at exposure (P = 0.09). We found no indication of effects of smoking, alcohol consumption and body mass index on the baseline risk of prostate cancer. The observed dose response strengthens the evidence of a radiation effect on the risk of prostate cancer incidence in the atomic bomb survivors.

ASSESSMENT OF OCCUPATIONAL RADIATION DOSES OF MEDICAL RADIATION WORKERS IN TWO COMMUNITY HOSPITALS

The International Commission on Radiological Protection recommends the adoption of the linear, no-threshold model as a predictive risk model for radiation protection purposes since the relationship between low-dose radiation exposure and cancer risk is unclear. Medical radiation workers are subject to occupational exposures and differences in workload, area of work and types of exposure can lead to variations in exposures between different occupational groups. We investigated the occupational exposures of 572 workers from four departments in two community hospitals and stratified into 22 occupational groups in order to identify groups with the highest radiation exposure. The occupational doses from 2015 to 2019 were analyzed to identify the dose distribution of each occupational group, total number of monitored workers, annual and collective deep (Hp(10)), eye (Hp(3)) and shallow (Hp(0.07)) doses. We further determined the individual and occupational group lifetime doses as well as the probability that monitored workers' lifetime doses will exceed a specified lifetime dose level. The occupational groups with the highest radiation exposures were the nuclear medicine technologists, diagnostic imaging radiologists and diagnostic cardiologists. Although our data suggest that occupational doses reported are low, it is essential that exposure of occupationally exposed personnel are always kept as low as reasonably achievable with an effective radiation protection program.

Lower abdominal and pelvic radiation and testicular germ cell tumor risk

Background

Testicular germ cell tumor (TGCT) incidence has increased in recent decades along with the use and dose of diagnostic radiation. Here we examine the association between reported exposure to diagnostic radiation and TGCT risk.

Methods

We conducted a case-control study of men with and without TGCT recruited from hospital- and population-based settings. Participants reported on exposures to 1) x-ray or CT below the waist and 2) lower GI series or barium enema, which consists of a series of x-rays of the colon. We also derived a combined measure of exposure. We used logistic regression to determine the risk of developing TGCT according to categories of exposures (0, 1–2, or ≥3 exposures) and age at first exposure, adjusting for age, year of birth, race, county, body mass index at diagnosis, family history of TGCT, and personal history of cryptorchidism.

Results

There were 315 men with TGCT and 931 men without TGCT in our study. Compared to no exposures, risk of TGCT was significantly elevated among those reporting at least three exposures to x-ray or CT (OR_{≥3 exposures}, 1.78; 95% CI, 1.15–2.76; p = 0.010), lower GI series or barium enema (OR_{≥3 exposures}, 4.58; 95% CI, 2.39–8.76; p<0.001), and the combined exposure variable (OR_{≥3 exposures}, 1.59; 95% CI, 1.05–2.42; p = 0.029). The risk of TGCT was elevated for those exposed to diagnostic radiation at age 0–10 years, compared to those first exposed at age 18 years or later, although this association did not reach statistical significance (OR, 2.00; 95% CI, 0.91–4.42; p = 0.086).

Conclusions

Exposure to diagnostic radiation below the waist may increase TGCT risk. If these results are validated, efforts to reduce diagnostic radiation doses to the testes should be prioritized.

Lifetime Mortality Risk from Cancer and Circulatory Disease Predicted from the Japanese Atomic Bomb Survivor Life Span Study Data Taking Account of Dose Measurement Error

Dosimetric measurement error is known to potentially bias the magnitude of the dose response, and can also affect the shape of dose response. In this report, generalized relative and absolute rate models are fitted to the latest Japanese atomic bomb survivor solid cancer, leukemia and circulatory disease mortality data (followed from 1950 through 2003), with the latest (DS02R1) dosimetry, using Bayesian techniques to adjust for errors in dose estimates and assessing other model uncertainties. Linear-quadratic models are fitted and used to assess lifetime mortality risks for contemporary UK, USA, French, Russian, Japanese and Chinese populations. For a test dose of 0.1 Gy absorbed dose weighted by neutron relative biological effectiveness, solid cancer, leukemia and circulatory disease mortality risks for a UK population using a generalized linear-quadratic relative rate model were estimated to be 3.88% Gy-1 [95% Bayesian credible interval (BCI): 1.17, 6.97], 0.35% Gy-1 (95% BCI: -0.03, 0.78) and 2.24% Gy-1 (95% BCI: -0.17, 13.76), respectively. Using a generalized absolute rate linear-quadratic model at 0.1 Gy, the lifetime risks for these three end points were estimated to be 3.56% Gy-1 (95% BCI: 0.54, 6.78), 0.41% Gy-1 (95% BCI: 0.01, 0.86) and 1.56% Gy-1 (95% BCI: -1.10, 7.21), respectively. There was substantial evidence of curvature for solid cancer (in particular, the group of solid cancers excluding lung, breast and stomach cancers) and leukemia, so that for solid cancer and leukemia, estimates of excess risk per unit dose were nearly doubled by increasing the dose from 0.01 to 1.0 Gy, with most of the increase occurring in the interval from 0.1 to 1.0 Gy. For circulatory disease, the dose-response curvature was inverse, so that risk per unit dose was nearly halved by going from 0.01 t o 1.0 Gy weighted absorbed dose, although there were substantial uncertainties. In general, there were higher radiation risks for females compared to males. This was true for solid cancer and circulatory disease overall, as well as for lung, breast, stomach and the group of other solid cancers, and was the case whether relative or absolute rate projection models were employed; however, for leukemia this pattern was reversed. Risk estimates varied somewhat between populations, with lower cancer risks in aggregate for China and Russia, but higher circulatory disease risks for Russia, particularly using the relative rate model. There was more pronounced variation for certain cancer sites and certain types of projection models, so that breast cancer risk was markedly lower in China and Japan using a relative rate model, but the opposite was the case for stomach cancer. There was less variation between countries using the absolute rate models for stomach cancer and breast cancer, but this was not the case for lung cancer and the group of other solid cancers, or for circulatory disease.

Clinicopathological characteristics and outcomes of metachronous rectal cancer in patients with a history of cervical cancer with and without remote radiotherapy: Reports of 45 cases

The purpose of this study was to report the clinicopathological characteristics and treatment outcomes of 45 rectal cancer patients who have a history of cervical cancer with or without remote radiotherapy. Twenty-nine patients (64.4%) with a history of cervical cancer treated with pelvic radiotherapy were classified as group A, 16 (35.6%) patients with a history of cervical cancer not treated with radiotherapy were classified as group B. The median duration between radiotherapy for cervical cancer and rectal adenocarcinoma diagnosis was 18 years. At the time of rectal cancer diagnosis, 5 (17.2%) patients presented stage I disease, 15 (51.7%) had stage II, 1 (3.4%) had stage III, and 8 (27.6%) had stage IV. The patients in group A had older age, higher rates of gross ulcerative lesions, low hemoglobin levels, and a lower rate of lymph node metastases. The patients with secondary rectal cancer developed after radiotherapy for cervical cancer usually presented with abnormal abdominal symptoms, such as proctitis, cystitis, or rectal fistula. Higher colostomy rate was found in this group of patients due to severe pelvic fibrosis or proctitis.

Age-specific and gender-specific radiation risks in paediatric angiography and interventional cardiology: conversion coefficients and risk reference values

OBJECTIVES

To estimate risk for exposure-induced cancer death (REID), organ-specific risks of exposure-induced cancer death (REIDHT) and associated conversion coefficients (CCREID:KAP=REID/kerma-area product (KAP), CCREIDHT:KAP=REIDHT/KAP) in paediatric cardiac catheterizations using data from radiation dose structured reports (RDSR). A novel risk surveillance tool consisting of age-specific and gender-specific risk reference values (RRVs) related to population cancer risk is suggested.

METHODS

The PCXMC v.2.0 code is used together with exposure-related information from RDSR from a cohort of 238 children to assess cancer risks and related conversion coefficients. The KAP corresponding to 1 in 1000 of increased REID is used to define age-specific and gender-specific KAP values to monitor risk in such patient cohorts, here denoted as RRVs.

RESULTS

The REID estimates ranged from below 1 up to 300 in 100,000, and the RRVs for the different age groups and gender ranged from 0.77 Gycm2 and 2.1 Gycm2 for neonates (female, male) to 11 Gycm2 and 25 Gycm2 for 15-year-olds (female, male). The CCREID:KAP and CCREIDHT:KAP decreased biexponentially with increased age, being notably higher for female patients.

CONCLUSIONS

Prominent risk contributing organs were the lungs and the (female) breast. The concept of age-specific and gender-specific RRVs related to population cancer risk is introduced and is intended to be used as a supporting tool for physicians performing such interventions.

ADVANCES IN KNOWLEDGE

Age-related and gender-related conversion coefficients for radiation risk, CCREID:KAP and CCREIDHT:KAP, are introduced and a novel risk surveillance concept, the RRV, is suggested for paediatric cardiac catheterizations.

Thyroid cancer risk factors and Pakistani University students' awareness towards its preventive practice

OBJECTIVES

Thyroid Cancer is one of the rarest cancers but its prevalence has been increasing worldwide for the last couple of decades.

METHODS

The data collection tool was designed to assess knowledge, awareness, perception, and attitude towards preventive practices of thyroid cancer in Pakistani university students. The data were collected over a duration of six months and a total number of 3722 students participated.

RESULTS

The knowledge of risk factors of thyroid cancer was an important parameter of this study. The students who knew all the early signs of thyroid cancer were 28.7%. In this study, the independent variables such as age, gender, demographic location, and financial status were found to be highly significant with knowledge, attitude towards warning signs of cancer, and the perception of students about developing thyroid cancer.

CONCLUSIONS

The participants were found to have poor knowledge about early signs of thyroid cancer. The study participants perception, behavior, and attitude towards preventive practices of thyroid cancer were found inadequate and appropriate measures on a National level should be taken to enhance the knowledge about preventive practices of thyroid cancer. Increasing knowledge and awareness shall help decrease the overall morbidity and mortality linked with thyroid carcinomas and thyroid diseases.

Individual response of humans to ionising radiation: governing factors and importance for radiological protection

Tissue reactions and stochastic effects after exposure to ionising radiation are variable between individuals but the factors and mechanisms governing individual responses are not well understood. Individual responses can be measured at different levels of biological organization and using different endpoints following varying doses of radiation, including: cancers, non-cancer diseases and mortality in the whole organism; normal tissue reactions after exposures; and, cellular endpoints such as chromosomal damage and molecular alterations. There is no doubt that many factors influence the responses of people to radiation to different degrees. In addition to the obvious general factors of radiation quality, dose, dose rate and the tissue (sub)volume irradiated, recognized and potential determining factors include age, sex, life style (e.g., smoking, diet, possibly body mass index), environmental factors, genetics and epigenetics, stochastic distribution of cellular events, and systemic comorbidities such as diabetes or viral infections. Genetic factors are commonly thought to be a substantial contributor to individual response to radiation. Apart from a small number of rare monogenic diseases such as ataxia telangiectasia, the inheritance of an abnormally responsive phenotype among a population of healthy individuals does not follow a classical Mendelian inheritance pattern. Rather it is considered to be a multi-factorial, complex trait.

Radiation risk of incident colorectal cancer by anatomical site among atomic bomb survivors: 1958-2009

Radiation effects on colorectal cancer rates, adjusted for smoking, alcohol intake and frequency of meat consumption and body mass index (BMI) by anatomical subsite (proximal colon, distal colon and rectum) were examined in a cohort of 105,444 atomic bomb survivors. Poisson regression methods were used to describe radiation-associated excess relative risks (ERR) and excess absolute rates (EAR) for the 1958-2009 period. There were 2,960 first primary colorectal cancers including 894 proximal, 871 distal and 1,046 rectal cancers. Smoking, alcohol intake and BMI were associated with subsite-specific cancer background rates. Significant linear dose-responses were found for total colon (sex-averaged ERR/Gy for 70 years old exposed at age 30 = 0.63, 95% confidence interval [CI]: 0.34; 0.98), proximal [ERR = 0.80, 95% CI: 0.32; 1.44] and distal colon cancers [ERR = 0.50, 95% CI: 0.04; 0.97], but not for rectal cancer [ERR = 0.023, 95% CI: -0.081; 0.13]. The ERRs for proximal and distal colon cancers were not significantly different (p = 0.41). The ERR decreased with attained age for total colon, but not for proximal colon cancer, and with calendar year for distal colon cancer. The ERRs and EARs did not vary by age at exposure, except for decreasing trend in EAR for proximal colon cancer. In conclusion, ionizing radiation is associated with increased risk of proximal and distal colon cancers. The ERR for proximal cancer persists over time, but that for distal colon cancer decreases. There continues to be no indication of radiation effects on rectal cancer incidence in this population.

Exposure to Tomographic Scans and Cancer Risks

BACKGROUND

Worldwide use of computed tomography (CT) scans has increased. However, the ionizing radiation from CT scans may increase the risk of cancer. This study examined the association between medical radiation from CT scans and the risk of thyroid cancer, lymphoma, and non-Hodgkin lymphoma (NHL) in adults.

METHODS

We conducted a nested case-control study in a cohort constructed from a population-based universal health insurance dataset in Taiwan in 2000-2013. In total, 22 853 thyroid cancer, 13 040 leukemia, and 20 157 NHL cases with their matched controls were included. Median follow-up times were 9.29-9.90 years for the three case-control groups. Medical radiation from CT scans was identified through physician order codes in medical insurance data from the index date to 3 years before a cancer diagnosis. Conditional logistic regression modeling was used for the overall and subsets of the population defined by sex and age groups to estimate the odds ratio (OR) and 95% confidence interval (CI) of the cancer risk associated with medical radiation.

RESULTS

Exposure to medical radiation from CT scans was associated with elevated risk of thyroid cancer (OR = 2.55, 95% CI = 2.36 to 2.75) and leukemia (OR = 1.55, 95% CI = 1.42 to 1.68). The elevated risk of thyroid cancer and leukemia in association with medical CT was stronger in women than in men. No statistically significant association between the risk of cancer and CT scans was observed in overall patients with NHL (OR = 1.05, 95% CI = 0.98 to 1.12); however, increased risks were found in patients aged 45 years or younger. A clear dose-response relationship was observed in patients 45 years or younger for all three cancers.

CONCLUSIONS

CT scans may be associated with an increased risk of thyroid cancer and leukemia in adults and in those diagnosed with NHL at a younger age.

Clinical and pathological characteristics of bladder cancer in post brachytherapy patients

The long-term risk of secondary malignancy is a potential late effect of brachytherapy. However, the time interval, anatomic site and histopathology are not well studied. We sought to characterize the bladder cancers that developed following treatment of prostate cancer with brachytherapy. Between 1998 and 2014, 4570 patients were treated with brachytherapy at the BC Cancer Agency. Out of those, 69 patients subsequently developed bladder cancer, some of which could have been radiation induced. Histology slides were reviewed for all cases, and site and pathologic features were recorded. Cases were classified as luminal and basal subtypes based on GATA3 and CK5/6 immunohistochemistry. Bladder neck and trigone were among the common sites of involvement. Pathologic review of cases showed that 68 % were high-grade, 25 % were muscle-invasive, and 20 % showed variant histology, including small cell carcinoma, sarcomatoid carcinoma, squamous cell carcinoma, and adenocarcinoma. A subgroup of cases more likely to be radiation-induced, based on site and time interval, was associated with increased pathologic stage (pT1 or higher) compared to the other cases (70 % vs 34 %, p = 0.01). In conclusion, the majority of bladder cancers following brachytherapy in this cohort were of high grade and low stage at diagnosis, most of them demonstrating luminal immunophenotype. A significant number of variant histologies are seen, each demonstrating a specific immunophenotype.

Diagnostic Reference Levels, Deterministic and Stochastic Risks in Pediatric Interventional Cardiology Procedures

To establish diagnostic reference levels (DRLs) and investigate deterministic and stochastic risks in pediatric interventional cardiology (IC) procedures. Exposure parameters were retrospectively reviewed for 373 patients treated between May 2016 and November 2018 at a single specialized hospital. Weight specific DRLs were derived for pediatric IC procedures. Additionally, peak skin dose (Dskin,max) was measured using thermoluminescent dosimeters for a sample of 7 diagnostic and 43 therapeutic procedures. Finally, using PCXMC software, organ doses were computed and the risk of exposure-induced cancer death (REID) was estimated using the risk models of the Biological Effects of Ionizing Radiation VII committee. DRLs for ventricular septal defect (VSD) occlusions, lacking in the literature, in terms of air kerma at patient entrance reference point (388 and 629 mGy) and total air kerma-area product (28 and 61 Gycm) were proposed for patients weight-groups 5 - < 15 kg and 15 - < 30 kg, respectively. The mean (range) Dskin,max was 15 (1-30) mGy and 94 (1-491) mGy for diagnostic and therapeutic procedures, respectively. Meanwhile, VSD occlusion involved the highest organ doses where the lungs, liver, stomach, and breasts mean doses were 57, 37, 6, and 10 mGy, respectively, and the associated REID were 0.5% and 0.3% in female and male patients, respectively. DRLs were proposed for pediatric IC procedures; these will help optimize patient exposure. Dskin,max values were lower than the 2 Gy threshold for skin injuries. Pediatric organ doses and the REID were the highest during VSD occlusion and may be critical for repetitive procedures.

Cancer incidence after childhood irradiation for tinea capitis in a Portuguese cohort

OBJECTIVES

Our aim was to compare cancer incidence in a cohort exposed in childhood (1950-63) to a therapeutic dose of radiation in the North of Portugal and followed-up until the end of 2012, with the incidence rates for the same age and sex in the general population.

METHODS

A population-based North Region cancer registry (RORENO) was used to assess which members of the cohort developed cancer. The association between radiation exposure and overall and specific cancer sites was evaluated using standardised incidence ratios (SIR).

RESULTS

Over the full follow-up period, 3357 individuals of the 5356 original tinea capitis (TC) cohort (63%) were retrieved in the RORENO, and 399 new cancer cases were identified, representing an increased risk of 49% when compared with the general population (SIR = 1.49; 95% CI: 1.35-1.64). The risk was slightly higher in males than in females (SIR = 1.65; 95% CI: 1.43-1.89 vs SIR = 1.35; CI = 1.17-1.55). The risk was slightly higher in the individuals exposed to a higher radiation dose (SIR = 1.78; 95% CI: 1.22-2.51 for ≥630 R vs SIR = 1.46; 95% CI: 1.31-1.62 for 325-475 R). In females, there was an excess cancer risk in all cancers with the higher radiation dose (SIR = 2.00; 95% CI: 1.21-3.13 for ≥630 R vs SIR = 1.30; 95% CI: 1.11-1.51 for 325-475 R) which was not observed in males, and for combined dose categories significantly raised SIRs for thyroid and head and neck cancer, suggesting a possible higher radiosensitivity of females. An increased risk was also observed for some cancers located far from the irradiated area.

CONCLUSIONS

The results suggest an association between radiation exposure and later increased cancer risk for cancers located near the radiation exposed area, mainly thyroid, and head and neck cancers. Further studies are necessary to disentangle possible non-radiation causes for distant cancers increased risk.

ADVANCES IN KNOWLEDGE

This paper shows a possible association between childhood X-ray epilation and increased risk of cancer which was not previously investigated in the Portuguese TC cohort.

What Can Chemical Carcinogenesis Shed Light on the LNT Hypothesis in Radiation Carcinogenesis?

To protect the public’s health from exposure to physical, chemical, and microbiological agents, it is important that any policy be based on rigorous scientifically based research. The concept of “linear no-threshold” (LNT) has been implemented to provide guideline exposures to these agents. The practical limitation to testing this hypothesis is to provide sufficient samples for experimental or epidemiological studies. While there is no universally accepted understanding of most human diseases, there seems to be better understanding of cancer that might help resolve the “LNT” model. The public’s concern, after being exposed to radiation, is the potential of producing cancer. The most rigorous hypothesis of human carcinogenesis is the “multistage, multimechanism” chemical carcinogenesis model. The radiation carcinogenesis LNT model, rarely, if ever, built it into their support. It will be argued that this multistage, multimechanism model of carcinogenesis, involving the “initiation” of a single cell by a mutagen event, followed by chronic exposure to threshold levels of epigenetic agents or conditions that stimulate the clonal expansion of the “initiated” cell, can convert these benign cells to become invasive and metastatic. This “promotion” process can be interrupted, thereby preventing these initiated cells from transitioning to the “progression” process of invasion and metastasis.

Association of Exposure to Diagnostic Low-Dose Ionizing Radiation With Risk of Cancer Among Youths in South Korea

IMPORTANCE

Diagnostic low-dose ionizing radiation has great medical benefits; however, its increasing use has raised concerns about possible cancer risks.

OBJECTIVE

To examine the risk of cancer after diagnostic low-dose radiation exposure.

DESIGN, SETTING, AND PARTICIPANTS

This population-based cohort study included youths aged 0 to 19 years at baseline from South Korean National Health Insurance System claim records from January 1, 2006, to December 31, 2015. Exposure to diagnostic low-dose ionizing radiation was classified as any that occurred on or after the entry date, when the participant was aged 0 to 19 years, on or before the exit date, and at least 2 years before any cancer diagnosis. Cancer diagnoses were based on International Statistical Classification of Diseases and Related Health Problems, Tenth Revision codes. Data were analyzed from March 2018 to September 2018.

MAIN OUTCOMES AND MEASURES

The primary analysis assessed the incidence rate ratios (IRRs) for exposed vs nonexposed individuals using the number of person-years as an offset.

RESULTS

The cohort included a total of 12 068 821 individuals (6 339 782 [52.5%] boys). There were 2 309 841 individuals (19.1%) aged 0 to 4 years, 2 951 679 individuals (24.5%) aged 5 to 9 years, 3 489 709 individuals (28.9%) aged 10 to 14 years, and 3 317 593 individuals (27.5%) aged 15 to 19 years. Of these, 1 275 829 individuals (10.6%) were exposed to diagnostic low-dose ionizing radiation between 2006 and 2015, and 10 792 992 individuals (89.4%) were not exposed. By December 31, 2015, 21 912 cancers were recorded. Among individuals who had been exposed, 1444 individuals (0.1%) received a cancer diagnosis. The overall cancer incidence was greater among exposed individuals than among nonexposed individuals after adjusting for age and sex (IRR, 1.64 [95% CI, 1.56-1.73]; P < .001). Among individuals who had undergone computed tomography scans in particular, the overall cancer incidence was greater among exposed individuals than among nonexposed individuals after adjusting for age and sex (IRR, 1.54 [95% CI, 1.45-1.63]; P < .001). The incidence of cancer increased significantly for many types of lymphoid, hematopoietic, and solid cancers after exposure to diagnostic low-dose ionizing radiation. Among lymphoid and hematopoietic cancers, incidence of cancer increased the most for other myeloid leukemias (IRR, 2.14 [95% CI, 1.86-2.46]) and myelodysplasia (IRR, 2.48 [95% CI, 1.77-3.47]). Among solid cancers, incidence of cancer increased the most for breast (IRR, 2.32 [95% CI, 1.35-3.99]) and thyroid (IRR, 2.19 [95% CI, 1.97-2.20]) cancers.

CONCLUSIONS AND RELEVANCE

This study found an association of increased incidence of cancer with exposure to diagnostic low-dose ionizing radiation in a large cohort. Given this risk, diagnostic low-dose ionizing radiation should be limited to situations in which there is a definite clinical indication.

Towards a New Concept of Low Dose

When people discuss the risks associated with low doses of ionizing radiation, central to the discussion is the definition of a low dose and the nature of harm. Standard answers such as "doses below 0.1 Gy are low" or "cancer is the most sensitive measure of harm" obscure the complexity within these seemingly simple questions. This paper will discuss some of the complex issues involved in determining risks to human and nonhuman species from low-dose exposures. Central to this discussion will be the role of communicable responses to all stressors (often referred to as bystander responses), which include recently discovered epigenetic and nontargeted mechanisms. There is a growing consensus that low-dose exposure to radiation is but one of many stressors to impact populations. Many of these stressors trigger responses that are generic and not unique to radiation. The lack of a unique radiation signature makes absolute definition of radiation risk difficult. This paper examines a possible new way of defining low dose based on the systemic response to the radiation. Many factors will influence this systemic response and, because it is inherently variable, it is difficult to predict and so makes low-dose responses very uncertain. Rather than seeking to reduce uncertainty, it might be valuable to accept the variability in outcomes, which arise from the complexity and multifactorial nature of responses to stressors.

Radiation and Risk of Liver, Biliary Tract, and Pancreatic Cancers among Atomic Bomb Survivors in Hiroshima and Nagasaki: 1958-2009

The Life Span Study (LSS) of atomic bomb survivors has consistently demonstrated significant excess radiation-related risks of liver cancer since the first cancer incidence report. Here, we present updated information on radiation risks of liver, biliary tract and pancreatic cancers based on 11 additional years of follow-up since the last report, from 1958 to 2009. The current analyses used improved individual radiation doses and accounted for the effects of alcohol consumption, smoking and body mass index. The study participants included 105,444 LSS participants with known individual radiation dose and no known history of cancer at the start of follow-up. Cases were the first primary incident cancers of the liver (including intrahepatic bile duct), biliary tract (gallbladder and other and unspecified parts of biliary tract) or pancreas identified through linkage with population-based cancer registries in Hiroshima and Nagasaki. Poisson regression methods were used to estimate excess relative risks (ERRs) and excess absolute risks (EARs) associated with DS02R1 doses for liver (liver and biliary tract cancers) or pancreas (pancreatic cancer). We identified 2,016 incident liver cancer cases during the follow-up period. Radiation dose was significantly associated with liver cancer risk (ERR per Gy: 0.53, 95% CI: 0.23 to 0.89; EAR per 10,000 person-year Gy: 5.32, 95% CI: 2.49 to 8.51). There was no evidence for curvature in the radiation dose response (P=0.344). ERRs by age-at-exposure categories were significantly increased among those who were exposed at 0-9, 10-19 and 20-29 years, but not significantly increased after age 30 years, although there was no statistical evidence of heterogeneity in these ERRs (P = 0.378). The radiation ERRs were not affected by adjustment for smoking, alcohol consumption or body mass index. As in previously reported studies, radiation dose was not associated with risk of biliary tract cancer (ERR per Gy: -0.02, 95% CI: -0.25 to 0.30). Radiation dose was associated with a nonsignificant increase in pancreatic cancer risk (ERR per Gy: 0.38, 95% CI: <0 to 0.83). The increased risk was statistically significant among women (ERR per Gy: 0.70, 95% CI: 0.12 to 1.45), but not among men.

The Risk of Developing Secondary Central Nervous System Tumors After Diagnostic Irradiation From Computed Tomography in Pediatrics: A Literature Review

BACKGROUND

Advanced diagnostic imaging has provided tremendous benefits; however, increased use of ionizing radiation modalities such as cranial computed tomography (CT) may be associated with an increased risk of developing central nervous system tumors.

METHODS

A literature review identified studies published for more than the last 50 years from 1968 to 2018 that explored the association between head CT scans and developing central nervous system tumors in pediatrics. We reviewed seven studies that described and analyzed the risk of brain tumors.

RESULTS

A positive correlation between exposure to CT scans and developing central nervous system tumors was evident in all cohorts. The strength of the association varied across the studies. Exclusion of patients with predisposing factors to central nervous system tumors was examined in four studies with a decreased risk to develop central nervous system tumors noted in three studies. Two studies reported nonsignificant reduction in the excess relative risk per milliGray of brain dose after adjusting for predisposing factors, whereas the reduction was significant in one study. The frequency of CT exposure was proportional to the risk of developing tumors in two studies although not significantly maintained in two other studies. Gender had no significant effect on the central nervous system tumor risk. The calendar year at the time of imaging showed decreasing risk in those exposed to CT in more recent years compared with prior decades.

CONCLUSIONS

Prospective epidemiologic studies are needed to examine the precise carcinogenic effect of exposure to ionizing radiation and help tailor further preventive measures.

Radiation-Related Risk of Cancers of the Upper Digestive Tract among Japanese Atomic Bomb Survivors

As a follow-up to the comprehensive work on solid cancer incidence in the Life Span Study (LSS) cohort of atomic bomb survivors between 1958 and 1998, we report here on updated radiation risk estimates for upper digestive tract cancers. In this study, we added 11 years of follow-up (1958-2009), used improved radiation dose estimates, considered effects of smoking and alcohol consumption and performed dose-response analyses by anatomical sub-site. In examining 52 years'worth of data, we ascertained the occurrence of 394 oral cavity/pharyngeal cancers, 486 esophageal cancers and 5,661 stomach cancers among 105,444 subjects. The radiation risk for oral cavity/pharyngeal cancer, other than salivary gland, was elevated but not significantly so. In contrast, salivary gland cancer exhibited a strong linear dose response with excess relative risk (ERR) of 2.54 per Gy [95% confidence interval (CI): 0.69 to 6.1]. Radiation risk decreased considerably with increasing age at time of exposure (-66% per decade, 95% CI: -88% to -32%). The dose response for esophageal cancer was statistically significant under a simple linear, linear-quadratic and quadratic model. Both linear-quadratic and quadratic models described the data better than a simple linear model and, of the two, the quadratic model showed a marginally better fit based on the Akaike Information Criteria. Sex difference in linear ERRs was not statistically significant; however, when the dose-response shape was allowed to vary by sex, statistically significant curvature was found among males, with no evidence of quadratic departure from linearity among females. The risk for stomach cancer increased significantly with dose and there was little evidence for quadratic departure from linearity among either males or females. The sex-averaged ERR at age 70 was 0.33 per Gy (95% CI: 0.20 to 0.47). The ERR decreased significantly (-1.93 power of attained age, 95% CI: -2.94 to -0.82) with increasing attained age, but not with age at exposure, and was higher in females than males (P = 0.02). Our results are largely consistent with the results of prior LSS analyses. Salivary gland, esophageal and stomach cancers continue to show significant increases in risk with radiation dose. Adjustment for lifestyle factors had almost no impact on the radiation effect estimates. Further follow-up of the LSS cohort is important to clarify the nature of radiation effects for upper digestive tract cancers, especially for oral cavity/pharyngeal and esophageal cancers, for which detailed investigation for dose-response shape could not be conducted due to the small number of cases.