Cumulative radiation exposure during follow-up after curative surgery for gastric cancer

Harmful effect of repetitive intravenous iodinated contrast media administration on the long-term renal function of patients with early gastric cancer

This retrospective study investigated whether repetitive exposure to intravenous iodinated contrast media (ICM) affects long-term renal function in patients who undergo curative surgery for early gastric cancer (EGC) collected from the Korean Health Insurance and Review Assessment (HIRA) database. Patients diagnosed with gastric cancer between January 2010 and December 2013 underwent regular computed tomography (CT) scans to monitor for extragastric recurrence. Patients who already had chronic kidney disease (CKD) before cancer diagnosis or had undergone chemotherapy or repeated surgery were excluded. A nested case-control study design was chosen to analyze the effect of repetitive ICM exposure to long-term renal function by comparing patients who developed CKD 2 years after cancer diagnosis and patients who did not. Among 59,971 patients collected according to inclusion and exclusion criteria, 1021 were diagnosed with CKD 2 years after cancer diagnosis. Using 1:5 matching after adjusting for age, sex and date of cancer diagnosis, 5097 control patients were matched to 1021 CKD patients. Conditional logistic regression showed that the number of CTs taken using ICM slightly increased the odds of CKD (odds ratio, 1.080; 95% confidence interval (CI): 1.059, 1.100; P < 0.0001). Thus, the administration of ICM might contribute to chronic renal function impairment.

Cumulative radiation doses due to nuclear medicine examinations: a systematic review

OBJECTIVES

To systematically review the published data regarding the cumulative exposure to radiation in selected cohorts of adults or paediatric patients due to diagnostic nuclear medicine examinations.

METHODS

We conducted PubMed/Medline searches of peer-reviewed papers on cumulated effective dose (CED) from diagnostic nuclear medicine procedures published between 01 January 2010 until 31 January 2021. Studies were considered eligible if the contribution of nuclear medicine examinations to total CED was >10%. Studies reporting cumulative doses in a single episode of care or in a limited time (≤1 year) were excluded. The main outcomes for which data were sought were the CED accrued by patients, the period in which the CED was accrued, the percentage of patients with CED > 100 mSv and the percentage contribution due to nuclear medicine procedures to the overall CED.

RESULTS

The studies included in the synthesis were 18 which enrolled a total of 1,76,371 patients. Eleven (1,757 patients), three (1,74,079 patients) and four (535 patients) were related to oncological, cardiologic and transplanted patients, respectively. All the studies were retrospective; some of the source materials referred to small number of patients and some of the patients were followed for a short time. Not many studies accurately quantified the contribution of nuclear medicine procedures to the overall radiation exposure due to medical imaging. Finally, most of the studies covered an observation period which extended mainly in the 2000-2010 decade.

CONCLUSIONS

There is a need of prospective, multicentric studies enrolling a greater number of patients, followed for longer period in selected groups of patients to fully capture the cumulative exposure to radiation in these settings.

ADVANCES IN KNOWLEDGE

This systematic review allows to identify selected group of patients with a specific health status in which the cumulated exposure to radiation may be of concern and where the contribution of nuclear medicine procedures to the total CED is significant.

Radiation dose from medical imaging in end stage renal disease patients: a Nationwide Italian Survey

BACKGROUND AND OBJECTIVES

End stage renal disease (ESRD) patients are exposed to the risk of ionizing radiation during repeated imaging studies. The variability in diagnostic imaging policies and the accompanying radiation doses across various renal units is still unknown. We studied this variability at the centre level and quantified the associated radiation doses at the patient level.

METHODS

Fourteen Italian nephrology departments enrolled 739 patients on haemodialysis and 486 kidney transplant patients. The details of the radiological procedures performed over one year were recorded. The effective doses and organ doses of radiation were estimated for each patient using standardized methods to convert exposure parameters into effective and organ doses RESULTS: Computed tomography (CT) was the major contributor (> 77%) to ionizing radiation exposure. Among the haemodialysis and kidney transplant patients, 15% and 6% were in the high (≥ 20 mSv per year) radiation dose groups, respectively. In haemodialysis patients, the most exposed organs were the liver (16 mSv), the kidney (15 mSv) and the stomach (14 mSv), while the uterus (6.2 mSv), the lung (5.7 mSv) and the liver (5.5 mSv) were the most exposed in kidney transplant patients. The average cumulative effective dose (CED) of ionizing radiation among centres in this study was highly variable both in haemodialysis (from 6.4 to 18.8 mSv per patient-year; p = 0.018) and even more so in kidney transplant (from 0.6 to 13.7 mSv per patient-year; p = 0.002) patients.

CONCLUSIONS

Radiation exposure attributable to medical imaging is high in distinct subgroups of haemodialysis and transplant patients. Furthermore, there is high inter-centre variability in radiation exposure, suggesting that nephrology units have substantially different clinical policies for the application of diagnostic imaging studies.

Stratification of Postsurgical Computed Tomography Surveillance Based on the Extragastric Recurrence of Early Gastric Cancer

OBJECTIVE

To stratify the postsurgical computed tomography (CT) surveillance based on a risk-scoring system for predicting extragastric recurrence after surgical resection of early gastric cancer (EGC).

SUMMARY OF BACKGROUND DATA

Postsurgical CT surveillance should not be routinely performed in all patients because of the low incidence of extragastric recurrence and potential risk of radiation exposure.

METHODS

Data from 3162 patients who underwent surgical resection for EGC were reviewed to develop a risk-scoring system to predict extragastric recurrence. Risk scores were based on the predictive factors for extragastric recurrence, which were determined using Cox proportional hazard regression model. The risk-scoring system was validated by Uno censoring adjusted C-index. External validation was performed using an independent dataset (n = 430).

RESULTS

The overall incidence of extragastric recurrence was 1.4% (44/3162). Five risk factors (lymph node metastasis, indications for endoscopic resection, male sex, positive lymphovascular invasion, and elevated macroscopic type), which were significantly associated with extragastric recurrence, were incorporated into the risk-scoring system, and the patients were categorized into 2 risk groups. The 10-year extragastric recurrence-free survival differed significantly between low- and high-risk groups (99.7% vs 96.5%; P < 0.001). The predictive accuracy of the risk-scoring system in the development cohort was 0.870 [Uno C-index; 95% confidence interval (95% CI), 0.800-0.939]. Discrimination was good after internal (0.859) and external validation (0.782, 0.549-1.000).

CONCLUSION

This risk-scoring system might be useful to predict extragastric recurrence of EGC after curative surgical resection. We suggest that postsurgical CT surveillance to detect extragastric recurrence should be avoided in the low-risk group.

More Frequent Follow-up CT Scans in Postsurgical Resection Patients Than in Postendoscopic Resection Patients of Early Gastric Cancers: Impracticality of CTs for Mucosal Cancer

RATIONALE AND OBJECTIVES

The aim of this study was to compare the utility and timing of computed tomography (CT) in the detection of recurrent tumors between patients after surgical and endoscopic resections for early gastric cancer (EGC).

MATERIALS AND METHODS

A total of 670 patients after surgical (n = 535) and endoscopic (n = 135) resections for EGC between 2007 and 2009 were enrolled. The mean numbers of CT and endoscopy between both treatment groups were compared. The mean and cumulative dose length products of CT examinations were calculated. The modality that detected recurrence was compared between the two groups using the Pearson chi-square test.

RESULTS

The mean interval of CT was significantly shorter and the mean number of CTs was significantly larger in the surgical resection group than in the endoscopic resection group. All 34 gastric recurrences were diagnosed by endoscopy. All seven extragastric recurrences occurred in patients treated for EGC with submucosal invasion. Six extragastric recurrences were detected by CT out of a total of 5417 CT scans. The average cumulative dose length product was significantly higher in the surgical group than in the endoscopic resection group (P = 0.004).

CONCLUSION

Follow-up CTs were performed more frequently in patients after surgical resection than in patients after endoscopic resection of EGCs. However, CT scans were not effective in detecting recurrent tumors after either treatment methods, especially for patients treated for mucosal gastric cancer.

Local or extragastric recurrence after incomplete endoscopic submucosal dissection of early gastric cancer: risk factors and the role of CT

PURPOSE

To investigate the risk factors of local and extragastric recurrence after incomplete endoscopic submucosal dissection (ESD) of early gastric cancer and the role of CT in the surveillance of extragastric recurrence.

METHODS

Institutional review board approval was obtained for this retrospective study with waiver of informed consent. From January 2005 to April 2017, 2086 ESDs were performed. Among them, 202 patients who received incomplete ESDs with positive lateral or deep margins comprised our study population(M:F = 108:94, mean age = 63.3 years). Histopathology, size and depth of the tumor, margin status, and the presence of lymphovascular invasion(LVI) were recorded. The patients were followed-up for a mean period of 38.5 months (range 0.8-139 months). Univariate and multivariate statistical analyses were performed to assess the risk factors of local and extragastric recurrence.

RESULTS

96 patients had (+) lateral margins, 90 had (+) deep margins and 16 had (+) lateral and deep margins. On subsequent surgery and follow-up, local gastric recurrence was found in 54 patients and extragastric recurrence was present in 13 patients. On multivariate analysis, (+) lateral margin [hazard radio (HR) 6.002; P < 0.0001] and tumor size(HR 1.372; P = 0.009) were demonstrated to be significant risk factors for local recurrence and (+) LVI was shown to be the only significant variable for extragastric recurrence(HR 6.798, P = 0.002).

CONCLUSION

A positive lateral margin and tumor size were significant risk factors for local recurrence while positive LVI was shown to be the only significant variable for extragastric recurrence. Therefore, if LVI is positive in patients who received incomplete ESD, subsequent surgery or follow-up with CT is recommended.

Age- and gender-specific estimates of cumulative CT dose over 5 years using real radiation dose tracking data in children

BACKGROUND

It is necessary to develop a mechanism to estimate and analyze cumulative radiation risks from multiple CT exams in various clinical scenarios in children.

OBJECTIVE

To identify major contributors to high cumulative CT dose estimates using actual dose-length product values collected for 5 years in children.

MATERIALS AND METHODS

Between August 2006 and July 2011 we reviewed 26,937 CT exams in 13,803 children. Among them, we included 931 children (median age 3.5 years, age range 0 days-15 years; M:F = 533:398) who had 5,339 CT exams. Each child underwent at least three CT scans and had accessible radiation dose reports. Dose-length product values were automatically extracted from DICOM files and we used recently updated conversion factors for age, gender, anatomical region and tube voltage to estimate CT radiation dose. We tracked the calculated CT dose estimates to obtain a 5-year cumulative value for each child. The study population was divided into three groups according to the cumulative CT dose estimates: high, ≥30 mSv; moderate, 10-30 mSv; and low, <10 mSv. We reviewed clinical data and CT protocols to identify major contributors to high and moderate cumulative CT dose estimates.

RESULTS

Median cumulative CT dose estimate was 5.4 mSv (range 0.5-71.1 mSv), and median number of CT scans was 4 (range 3-36). High cumulative CT dose estimates were most common in children with malignant tumors (57.9%, 11/19). High frequency of CT scans was attributed to high cumulative CT dose estimates in children with ventriculoperitoneal shunt (35 in 1 child) and malignant tumors (range 18-49). Moreover, high-dose CT protocols, such as multiphase abdomen CT (median 4.7 mSv) contributed to high cumulative CT dose estimates even in children with a low number of CT scans.

CONCLUSION

Disease group, number of CT scans, and high-dose CT protocols are major contributors to higher cumulative CT dose estimates in children.

Cumulative effective dose associated with computed tomography examinations in adolescent trauma patients

OBJECTIVES

The aims of this study were to analyze cumulative effective dose (cED) and to assess lifetime attributable risk (LAR) of cancer due to radiation exposure during computed tomography (CT) examinations in adolescent trauma patients.

METHODS

Between January 2010 and May 2011, the adolescent patients with trauma were enrolled in this study. Numbers of CT examinations and body regions examined were collated, and cEDs were calculated using dose-length product values and conversion factors. Lifetime attributable risk for cancer incidence and cancer-associated mortality were quantified based on the studies of survivors of the atomic bombs on Japan. Data were stratified according to severity of trauma: minor trauma, injury severity score of less than 16; and major trauma, injury severity score of 16 or greater.

RESULTS

A total of 698 CT scans were obtained on the following regions of 484 adolescent patients: head CT, n = 647; rest of the body, n = 41; and thorax, n = 10. Mean cED per patient was 3.4 mSv, and mean LARs for cancer incidence and mortality were 0.05% and 0.02%, respectively. The majority of patients (98.4%) experienced minor trauma, and their mean cED and LARs for cancer incidence and mortality (3.0 mSv and 0.04% and 0.02%, respectively) were significantly lower than those of patients with major trauma (24.3 mSv and 0.31% and 0.15%, respectively, all P values < 0.001).

CONCLUSIONS

The overall radiation-induced cancer risk due to CT examinations performed for the initial assessment of minor trauma was found to be relatively low in adolescent patients. However, adolescent patients with major trauma were exposed to a substantial amount of radiation during multiple CT examinations.

Diagnostic radiation exposure of injury patients in the emergency department: a cross-sectional large scaled study

In contrast to patients with underlying cancer or chronic disease, injury patients are relatively young, and can be expected to live their natural lifespan if injuries are appropriately treated. Multiple and repeated diagnostic scans might be performed in these patients during admission. Nevertheless, radiation exposure in injury patients has been overlooked and underestimated because of the emergent nature of such situations. Therefore, we tried to assess the cumulative effective dose (cED) of injury patients in the emergency department. We included patients who visited the emergency department (ED) of a single tertiary hospital due to injury between February 2010 and February 2011. The cED for each patient was calculated and compared across age, sex and injury mechanism. A total of 11,676 visits (mean age: 28.0 years, M:F = 6,677:4,999) were identified. Although CT consisted of only 7.8% of total radiologic examinations (n=78,025), it accounted for 87.1% of the total cED. The mean cED per visit was 2.6 mSv. A significant difference in the cED among injury mechanisms was seen (p<0.001) and patients with traffic accidents and fall down injuries showed relatively high cED values. Hence, to reduce the cED of injury patients, an age-, sex- and injury mechanism-specific dose reduction strategy should be considered.

Current opinions on medical radiation: a survey of oncologists regarding radiation exposure and dose reduction in oncology patients

PURPOSE

The aim of this study was to evaluate oncologists' opinions about the use of ionizing radiation in medical imaging of oncology patients.

METHODS

An electronic survey was e-mailed to 2,725 oncologists at the top 50 National Cancer Institute-funded cancer centers. The survey focused on opinions on CT dose reduction in oncology patients and current philosophies behind long-term imaging in these patients.

RESULTS

The response rate was 15% (415 of 2,725). Eighty-two percent of respondents stated that their patients or families have expressed anxiety regarding radiation dose from medical imaging. Although fewer than half of oncologists (48%) did not know whether CT dose reduction techniques were used at their institutions, only 25% were concerned that small lesions may be missed with low-dose CT techniques. The majority of oncologists (63%) follow National Comprehensive Cancer Network guidelines for imaging follow-up, while the remainder follow other national guidelines such as those of the Children's Oncology Group, the American Society of Clinical Oncology, or clinical trials. Ninety percent of respondents believe that long-term surveillance in oncology patients is warranted, particularly in patients with breast cancer, melanoma, sarcoma, and pediatric malignancies. The majority of oncologists would consider the use of low-dose CT imaging in specific patient populations: (1) children and young women, (2) those with malignancies that do not routinely metastasize to the liver, and (3) patients undergoing surveillance imaging.

CONCLUSIONS

Cumulative radiation exposure is a concern for patients and oncologists. Among oncologists, there is support for long-term imaging surveillance despite lack of national guidelines.

National survey of radiation doses of pediatric chest radiography in Korea: analysis of the factors affecting radiation doses

OBJECTIVE

To investigate radiation doses in pediatric chest radiography in a national survey and to analyze the factors that affect radiation doses.

MATERIALS AND METHODS

The study was based on the results of 149 chest radiography machines in 135 hospitals nationwide. For each machine, a chest radiograph was obtained by using a phantom representing a 5-year-old child (ATOM® dosimetry phantom, model 705-D, CIRS, Norfolk, VA, USA) with each hospital's own protocol. Five glass dosimeters (M-GD352M, Asahi Techno Glass Corporation, Shizuoka, Japan) were horizontally installed at the center of the phantom to measure the dose. Other factors including machine's radiography system, presence of dedicated pediatric radiography machine, presence of an attending pediatric radiologist, and the use of automatic exposure control (AEC) were also evaluated.

RESULTS

The average protocol for pediatric chest radiography examination in Korea was 94.9 peak kilovoltage and 4.30 milliampere second. The mean entrance surface dose (ESD) during a single examination was 140.4 microgray (µGy). The third quartile, median, minimum and maximum value of ESD were 160.8 µGy, 93.4 µGy, 18.8 µGy, and 2334.6 µGy, respectively. There was no significant dose difference between digital and non-digital radiography systems. The use of AEC significantly reduced radiation doses of pediatric chest radiographs (p < 0.001).

CONCLUSION

Our nationwide survey shows that the third quartile, median, and mean ESD for pediatric chest radiograph is 160.8 µGy, 93.4 µGy, and 140.4 µGy, respectively. No significant dose difference is noticed between digital and non-digital radiography systems, and the use of AEC helps significantly reduce radiation doses.