Dose-dependent expression of extracellular microRNAs in HCT116 colorectal cancer cells exposed to high-dose-rate ionising radiation.

Biomarkers of tumour response to radiotherapy may help optimise cancer treatment. The aim of the present study was to identify changes in extracellular microRNAs (miRNAs) as a biomarker of radiation-induced damage to human colorectal cancer cells. HCT116 cells were exposed to increasing doses of X-rays, and extracellular miRNAs were analysed by microarray. The results were correlated with the frequency of micronuclei. A total of 59 miRNAs with a positive correlation and 4 with a negative correlation between dose (up to 6 Gy) and extracellular miRNA expression were identified. In addition, for doses between 0 and 10 Gy, 12 miRNAs among those 59 miRNAs with a positive correlation were identified; for these extracellular miRNAs, a significantly positive correlation was observed between their expression and the frequency of micronuclei for doses up to 10 Gy. These results suggest that specific miRNAs may be considered as cell damage markers and may serve as secreted radiotherapy response biomarkers for colorectal cancer; however, the results must be further validated in serum samples collected from patients undergoing radiotherapy.

HER2-positive breast cancer that resists therapeutic drugs and ionizing radiation releases sphingomyelin-based molecules to circulating blood serum.

Breast cancer is the second most common cancer in the world based on incidence, reaching more than 2 million new cases in 2018, while continuing to increase. Invasive ductal carcinoma is the most common type of this cancer, making up approximately 70-80% of all breast cancer diagnoses. In particular, the type of breast cancer overexpressing human epidermal growth factor receptor 2 (HER2) has potential of strong proliferation, migration and invasion and early treatment is necessary. The authors identified and studied a single patient displaying complete therapeutic resistance to monoclonal anti-HER2 antibody therapy, chemotherapy and radiotherapy. A patient who exhibited resistance to postoperative adjuvant therapy after mastectomy was selected from HER2-positive breast cancer, and this patient had the grade of T4bN2aM0, Stage IIIB. The patient samples, blood serum and cancer tissue, were analyzed by metabolome and immunostaining technique, respectively. The characteristics of peripheral blood serum and solid tumor were investigated, aiming to find new serum biomarker(s) using the metabolomics technique. A correlation between the appearance of HER2-positive cancer tissue and serum concentration of the sphingomyelin family was found. In addition, HER2-positive tumor tissue in both the primary and recurrent cancer express the sphingomyelinase. These results suggest that sphingomyelins from this cancer tissue leads to therapy resistance, induction of invasion and strong proliferation.

Tomato Juice Consumption Could Improve Breast Skin Adverse Effects of Radiotherapy in Breast Cancer Patients.

BACKGROUND/AIM: We investigated the beneficial effects of drinking tomato juice (TJ) rich in antioxidant carotenoids on irradiated skin following radiotherapy (RT) in breast cancer patients. PATIENTS/METHODS: Twenty-three patients agreed to drink TJ (160 g/day for six months) after the completion of RT. Early and late adverse events (AEs) of irradiated skin were evaluated according to the Common Terminology Criteria for AEs and the European Organization for Research and Treatment of Cancer Global Cosmetic Rating System, respectively. RESULTS: With regard to early AEs, acute radiodermatitis of grade 1 was observed in most patients (22/23) at the end of RT. However, the grade of radiodermatitis rapidly changed to 0, 1 month after RT and starting TJ consumption. With regard to late AEs, most patients were in good or excellent dermal condition. CONCLUSION: TJ consumption could help in relieving and recovering from early AEs and decreasing the severity of late AEs of irradiated skin.

Safety and Feasibility of Radiation Therapy to the Primary Tumor in Patients With Metastatic Castration-resistant Prostate Cancer.

INTRODUCTION: The objective of this study was to evaluate the safety and feasibility of radiation therapy (RT) to the primary tumor in patients with metastatic castration-resistant prostate cancer (mCRPC). PATIENTS AND METHODS: This retrospective study included 105 patients with mCRPC who were treated between April 2004 and May 2019. We divided the patients into 2 groups: patients treated with RT to the primary tumor after they developed CRPC (RT group) and without (non-RT group). The primary purpose was safety assessed using the Common Terminology Criteria for Adverse Events. The secondary purpose included prostate-specific antigen (PSA) response, cancer-specific survival (CSS), and overall survival (OS). Background-adjusted multivariate analyses, with the inverse probability of treatment weighting (IPTW) method, were performed to evaluate impact of RT on CSS and OS. RESULTS: The median age at CRPC diagnosis was 75 years, and the median follow-up period after CRPC diagnosis was 21 months. The adverse events rates related to RT in any grade and grade ≥ 3 were 55% and 23%, respectively. Nine (29%) patients achieved ≥ 30% PSA decline with RT. In multivariate analyses with the IPTW method, the CSS and OS in the RT group were significantly longer than those in the non-RT group. In subgroup analyses with the IPTW method, RT was significantly associated with improved OS in patients aged ≥ 75 years and patients with initial PSA ≥ 500 ng/mL, cT4, Gleason score ≥ 8, and high-volume metastatic burden. CONCLUSIONS: RT to the primary tumor is safe and feasible, and it has potential benefits on oncologic outcomes in patients with mCRPC.

Association between Regional Cerebral Blood Flow and Mini-Mental State Examination Score in Patients with Alzheimer's Disease.

BACKGROUND: In patients with Alzheimer's disease (AD), cerebral blood flow (CBF) is decreased from the early stages. CBF in AD is currently estimated from Z-scores using statistical analysis. However, the Z-score is not considered the impaired area ratio. METHODS: In the present study, a novel indicator, ΣzS, associated with brain surface area and Zscores, is defined and the association with regional CBF has been estimated using Mini-Mental State Examination (MMSE) scores, which indicate the severity of cognitive impairment in patients with AD. RESULTS: A negative correlation was detected between ΣzS in the posterior cingulate gyrus and the subset numbers 1, 2, and 5 of the total MMSE scores. Furthermore, a negative correlation was detected between the total MMSE score and ΣzS in Brodmann area 30, which is a subdivided area of the brain. CONCLUSION: These results suggest that ΣzS may be a useful indicator of CBF metabolism, and thus may improve the current understanding of cognitive function in patients with AD.

Effectiveness of the smoothing filter in pediatric 99mTc-dimercaptosuccinic acid renal scintigraphy.

The present study aimed to evaluate whether the use of a smoothing filter would improve the image quality in pediatric 99mTc-dimercaptosuccinic acid (99mTc-DMSA) scintigraphy. We retrospectively reviewed 31 kidneys in 16 consecutive pediatric patients aged 10 months to 14 years. The administered dose was calculated using a weight-based method. Two reviewers randomly evaluated the original planar posterior images and smoothing filter image; they assessed image quality and performed defect evaluations. The evaluation of visual image quality yielded significantly better results for the smoothing filter images than for the original images. Although the smoothing filter images were slightly inferior to the original images in terms of edge sharpness, no significant difference was observed in the defect evaluation. We confirmed that 99mTc-DMSA scintigraphy with a smoothing filter yielded reduced image noise, while maintaining defect evaluation performance and improving image quality.

Quantitative assessment of radiodermatitis through a non-invasive objective procedure in patients with breast cancer.

Assessment of skin condition is necessary for providing advice regarding skin self-care to patients with breast cancer who have undergone radiation therapy. Acute and chronic phases of radiodermatitis were analyzed in patients using objective assessment tools in the present study. A total of 18 women who received radiation therapy for breast cancer were enrolled in the present study and their skin surface temperature (SST), hydration level of the skin surface (HL), melanin intensity (MI) and erythema intensity (EI) were measured prior to radiation therapy and six months thereafter. Furthermore, skin condition was assessed using the Common Terminology Criteria for Adverse Events (CTCAE). EI and MI levels at the irradiated site peaked upon the completion of radiation therapy and declined to baseline at 6 months. In contrast, SST levels were elevated at the irradiated site during radiation therapy (P<0.05) and plateaued after its completion. The same parameters in non-irradiated control sites remained unchanged during the study period. HL reached the minimum in irradiated and non-irradiated sites upon completion of radiation therapy. Although HL returned to baseline in the non-irradiated site 6 months after radiation therapy, it remained low in the irradiated site. No relationship between the CTCAE and EI level was observed. In conclusion, the present study demonstrated that objective assessment tools, including SST and EI levels, were useful for assessing skin condition during radiodermatitis. The combination of the CTCAE and objective assessment tools will enable a more accurate assessment of radiodermatitis.

Influence of anticoagulants and storage temperatures on blood counts and mitotic index of blood samples collected for cytogenetic biodosimetry.

PURPOSE: In order to establish suitable protocols of blood culture to obtain sufficient numbers of metaphases for dicentric chromosome assay (DCA), we have examined the effect of storage temperature, storage time, and anticoagulant type. MATERIALS AND METHODS: Peripheral blood was collected from five healthy donors with lithium heparin and ethylenediaminetetraacetic acid dipotassium salt (EDTA-2K). These samples were irradiated with X-rays at 3 Gy or sham; the samples were further divided into groups that were either stored at room temperature (RT) or 5.2 ± 1.0 °C. After 6, 24, 48, 72, and 168 h of storage, both blood counts and the mitotic index (MI) were analyzed. RESULTS: Heparinized blood samples stored under cold conditions exhibited low white blood cell, lymphocyte, and platelet counts. EDTA-treated blood samples did not show such obvious changes in cell counts. After 6 h of storage, heparinized blood samples stored at RT had MI of 21.5-29.3%. Similar MI was obtained in the EDTA-washed group stored for 6, 24, 48, and 72 h. CONCLUSIONS: Our study confirms that heparinized blood samples should be stored at RT to get sufficient metaphases for DCA, and that EDTA blood samples also can be used for blood culture after washing and storage under 5.2 ± 1.0 °C.

Mental and physical stress of the Fukushima disaster evacuees as estimated by the measurement of urinary 8-hydroxy-2'-deoxyguanosine.

Following the accident at the Fukushima Daiichi Nuclear Power Plant in 2011, a number of evacuees were forced to live in temporary housing and suffered mental and physical stress. However, few reports have used objective or quantitative indicators to determine the evacuee's level of stress. The aim of the present study was to serially estimate the mental and physical stress of the evacuees from 2013 to 2015 by using the oxidative stress marker, urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG). A total of 773 evacuees from Namie town in Fukushima prefecture participated in the study. In the first year, 486 evacuees participated (age, 62.8±18.2 years; male/female, 217/269). Of these, 127 continually participated in the study for 3 years (age, 69.5±13.5 years; males/female 52/75) and 18.1% had no chronic disease after the first year. Urine samples were collected once per year. Urinary 8-OHdG was measured using immunochromatography and corrected by the concentration of urinary creatinine. For all the participants examined each year, mean values of urinary 8-OHdG significantly increased over time. For the 127 continual participants, mean values of urinary 8-OHdG were significantly higher in 2014 and 2015 than those in 2013. Age, gender and presence of chronic disease did not significantly influence the 8-OHdG values, suggesting that the stress level of the evacuees was not associated with these factors. The stress level of the individuals increased with the length of time spent living in the temporary housing. The evacuees in radiation disasters have different stressors from other natural disasters, which may accelerate mental and physical stress.

Serum miR-375-3p increase in mice exposed to a high dose of ionizing radiation.

Exposure to high-doses of ionizing radiation (IR) leads to development of a strong acute radiation syndrome (ARS) in mammals. ARS manifests after a latency period and it is important to develop fast prognostic biomarkers for its early detection and assessment. Analysis of chromosomal aberrations in peripheral blood lymphocytes is the gold standard of biological dosimetry, but it fails after high doses of IR. Therefore, it is important to establish novel biomarkers of exposure that are fast and reliable also in the high dose range. Here, we investigated the applicability of miRNA levels in mouse serum. We found significantly increased levels of miR-375-3p following whole body exposure to 7 Gy of X-rays. In addition, we analyzed their levels in various organs of control mice and found them to be especially abundant in the pancreas and the intestine. Following a dose of 7 Gy, extensive cell death occurred in these tissues and this correlated negatively with the levels of miR-375-3p in the organs. We conclude that high expressing tissues of miR-375-3p may secrete this miRNA in serum following exposure to 7 Gy. Therefore, elevated miR-375-3p in serum may be a predictor of tissue damage induced by exposure to a high radiation dose.

Estimation of effective doses in pediatric X-ray computed tomography examination.

X-ray computed tomography (CT) images are used for diagnostic and therapeutic purposes in various medical disciplines. In Japan, the number of facilities that own diagnostic CT equipment, the number of CT examinations and the number of CT scanners increased by ~1.4-fold between 2005 and 2011. CT operators (medical radiological technologists, medical physicists and physicians) must understand the effective doses for examinations at their own institutions and carefully approach each examination. In addition, the patients undergoing the examination (as well as his/her family) must understand the effective dose of each examination in the context of the cumulative dose. In the present study, the numbers of pediatric patients (aged 0-5 years) and total patients who underwent CT at Hirosaki University Hospital (Hirosaki, Japan) between January 2011 and December 2013 were surveyed, and effective doses administered to children aged 0, 1 and 5 years were evaluated. Age- and region-specific conversion factors and dose-length products obtained from the CT scanner were used to estimate the effective doses. The numbers of CT examinations performed in 2011, 2012 and 2013 were 16,662, 17,491 and 17,649, respectively, of which 613 (1.2%) of the overall total involved children aged 0-5 years. The estimated effective doses per examination to children aged 0, 1 and 5 years were 6.3±4.8, 4.9±3.8 and 2.7±3.0 mSv, respectively. This large variation was attributed to several factors associated with scan methods and ranges in actual setting. In conclusion, the requirement for individual patient prospective exposure management systems and estimations of low-dose radiation exposure should be considered in light of the harmful effects of exposure.

Impact of time interval and dose rate on cell survival following low-dose fractionated exposures.

Enhanced cell lethality, also known as hyper-radiosensitivity, has been reported at low doses of radiation (≤0.5 Gy) in various cell lines, and is expected to be an effective cancer therapy. We conducted this study to examine the impact of time interval and dose rate of low-dose fractionated exposures with a short time interval. We evaluated the cell-survival rates of V79 and A549 cells using clonogenic assays. We performed fractionated exposures in unit doses of 0.25, 0.5, 1.0 and 2.0 Gy. We exposed the cells to 2 Gy of X-rays (i) at dose-rates of 1.0, 1.5 and 2.0 Gy/min at 1-min intervals and (ii) at a dose-rate of 2.0 Gy/min at 10-s, 1-min and 3-min intervals by fractionated exposures. Apoptosis and cell cycle analyses were also evaluated in the fractionated exposures (unit dose 0.25 Gy) and compared with single exposures by using flow cytometry. Both cell-type survival rates with fractionated exposures (unit dose 0.25 Gy) with short time intervals were markedly lower than those for single exposures delivering the same dose. When the dose rates were lower, the cytotoxic effect decreased compared with exposure to a dose-rate of 2.0 Gy/min. On the other hand, levels of apoptosis and cell cycle distribution were not significantly different between low-dose fractionated exposures and single exposures in either cell line. These results indicate that a stronger cytotoxic effect was induced with low-dose fractionated exposures with a short time interval for a given dose due to the hyper-radiosensitivity phenomenon, suggesting that dose rates are important for effective low-dose fractionated exposures.

Possible benefits of tomato juice consumption: a pilot study on irradiated human lymphocytes from healthy donors.

BACKGROUND: Reactive oxygen species (ROS) mediate much of the DNA damage caused by ionizing radiation. Among carotenoids, lycopene and ß-carotene, present in tomato juice, are known to be strong radical scavengers. The aim of the study was to investigate the effect of tomato juice intake on the levels of DNA damage and oxidative stress in human whole blood induced by in vitro exposure to X-rays. METHODS: Ten healthy adults were asked to drink 190 g of tomato juice, containing 17 mg lycopene and 0.25 mg ß-carotene, per day for 3 weeks and then refrain from drinking it for 3 weeks. Peripheral whole blood samples were collected before and after the intake period of tomato juice and after the washout period. The blood samples were exposed in vitro to X-ray doses of 0, 0.1, 0.5, and 2 Gy. Cytogenetic damage was measured using the cytokinesis-block micronucleus (CBMN) assay and the dicentrics (DIC) assay. The level of oxidative stress was determined using serum 8-oxo-7, 8-dihydro-2-deoxyguanosine (8-oxo-dG) and plasma reactive oxygen metabolite-derived compounds (d-ROMs). The concentration of carotenoids in plasma was measured at the three time points. RESULTS: The levels of 8-oxo-dG tended to decrease during the intake period and increase during the washout period. A non-significant inverse correlation was noted between the plasma concentration of lycopene plus ß-carotene and the level of 8-oxo-dG (P = 0.064). The radiation-induced MN and DIC frequencies increased in a dose-dependent manner, and when compared at the same dose, the MN and DIC frequencies decreased during the intake period compared with those at baseline and then increased during the washout period. The results suggest that continuous tomato juice consumption non-significantly decreases extracellular 8-oxo-dG, d-ROMs, and MN. Tomato juice intake had minimal or no effect on radiation-induced 8-oxo-dG and d-ROMs. For most radiation doses, continuously tomato juice intake lowered the levels of MN and DIC. CONCLUSION: Tomato juice consumption may suppress human lymphocyte DNA damage caused by radiation, but further examination is required. TRIAL REGISTRATION: 2014-001 and 2014-R06.

Application of cell sorting for enhancing the performance of the cytokinesis-block micronucleus assay.

Among the numerous methods available to assess genotoxicity, the cytokinesis-block micronucleus (CBMN) assay is very popular due its relative simplicity and power to detect both clastogenic and aneugenic compounds. A problem with the CBMN assay is that all DNA damaging agents also inhibit the ability of cells to progress through mitosis, leading to a low number of binucleated cells (BNCs). One method to resolve this issue is to ensure a sufficient proportion of BNCs in the samples. In the current study, the applicability of a cell sorting system capable of isolating cell fractions containing abundant BNCs was investigated. Furthermore, to investigate the relationship between the cell division delay due to radiation exposure and the generation of BNCs and micronuclei (MN), we assessed a series of lag times between radiation exposure and addition of cytochalasin-B (Cyt-B). Cells from the human chronic myelogenous leukemia cell line K562 were exposed to X-rays (2 Gy and 4 Gy), and Cyt-B was subsequently added at 0, 6 and 12 h following irradiation. After treatment with Cyt-B for 24 h, the percentage of BNCs, the MN frequency and the cell cycle distribution were analyzed. In addition, cells displaying the DNA contents corresponding to BNCs were isolated and analyzed. The results indicate that applying the cell sorter to the CBMN assay increased the percentage of BNCs compared with the standard method. Thus, this technique is a promising way of enhancing the capacity of the CBMN assay.

Predictive factors of cytotoxic damage in radioactive iodine treatment of differentiated thyroid cancer patients.

Radioactive iodine (131I) therapy in patients suffering from differentiated thyroid cancer (DTC) is a targeted treatment commonly used for thyroid ablation and locoregional and distant metastatic spread management. Despite a significant proportion of the 131I dose entering the circulation, there is currently no detailed information regarding its effect on the blood cell system. In order to assess the cytotoxic effects of 131I therapy on the circulatory system, blood cell levels, thyroid-related hormones and CD45+ cell cytotoxicity were estimated in blood collected from patients with DTC. The micronuclei (MN) frequency of the peripheral blood CD45+ cell fraction was significantly increased after 30 days of 131I therapy compared to that prior to treatment, although a strong individual variation was observed. A significantly negative correlation between MN frequency and the level of platelets and plateletcrit was observed; however, there was no such correlation with thyroid-related hormones. These resultS suggest that the correlation between MN frequency and the platelet system may serve as a biomarker of exposure and, possibly, of sensitivity in DTC patients undergoing 131I therapy following thyroid and lymph node surgery.

Estimation of internal exposure of the thyroid to (131)I on the basis of (134)Cs accumulated in the body among evacuees of the Fukushima Daiichi Nuclear Power Station accident.

Namie Town was heavily contaminated by the Fukushima Daiichi Nuclear Power Station accident. The thyroid equivalent dose for residents who lived in Namie was estimated using results of whole body counting examinations which were carried out by the Japan Atomic Energy Agency a few months after the nuclear accident. Photon peaks of (131)I and (134)Cs were previously measured by the authors using a NaI(Tl) scintillation spectrometer and that information was used to estimate the (131)I/(134)Cs activity ratio of total intake in the present study. The maximum values of (131)I/(134)Cs activity ratio corresponding to thyroid uptake factors of 0.3, 0.1 and 0.03 were evaluated to be 0.9, 2.6 and 8.7, respectively. The maximum value of the (131)I/(134)Cs activity ratio was used to obtain the most conservative thyroid equivalent dose estimation. The maximum internal exposure of the thyroid to (131)I on the basis of (134)Cs accumulated in the body measured by the whole body counter was estimated to be 18mSv. This value was much smaller than 50mSv that the International Atomic Energy Agency recommends as the dose at which exposed persons should take stable iodine tablets.

Activity concentrations of environmental samples collected in Fukushima Prefecture immediately after the Fukushima nuclear accident.

Radionuclide concentrations in environmental samples such as surface soils, plants and water were evaluated by high purity germanium detector measurements. The contribution rate of short half-life radionuclides such as (132)I to the exposure dose to residents was discussed from the measured values. The highest values of the (131)I/(137)Cs activity ratio ranged from 49 to 70 in the environmental samples collected at Iwaki City which is located to the south of the F1-NPS. On the other hand, the (132)I/(131)I activity ratio in the same environmental samples had the lowest values, ranging from 0.01 to 0.02. By assuming that the (132)I/(131)I activity ratio in the atmosphere was equal to the ratio in the environmental samples, the percent contribution to the thyroid equivalent dose by (132)I was estimated to be less than 2%. Moreover, the contribution to the thyroid exposure by (132)I might be negligible if (132)I contamination was restricted to Iwaki City.

Quantification of Epstein-Barr virus DNA is helpful for evaluation of chronic active Epstein-Barr virus infection.

Chronic active Epstein-Barr virus infection (CAEBV) presents with chronic or recurrent infectious mononucleosis-like symptoms, such as low-grade fever, liver dysfunction, lymphadenopathy, and hepatosplenomegaly. Immunological methods are useful for the diagnosis of viral infections. However, CAEBV patients do not necessarily have high titers of Epstein-Barr virus (EBV)-specific antibodies. Hosts that are immunocompromised after hematopoietic stem cell transplantations sometimes suffer from systemic EBV-associated hemophagocytic lymphohistiocytosis (EBV-HLH) and EBV-positive lymphoma. Patients with EBV-associated diseases are often diagnosed by analyses of bone marrow. Cytomegalovirus (CMV) can cause serious pneumonia or retinitis in immunocompromised hosts. In order to noninvasively understand the clinical status of patients with EBV-associated diseases, we conducted real-time polymerase chain reaction (PCR) methods in their peripheral blood in order to quantify EBV and CMV DNA levels, which reflect viral activity. Here, we describe a 30-year-old Japanese female patient with CAEBV. The patient had repeated fever, fatigue, and liver dysfunction. The histopathological results of liver biopsies were positive for EBV-encoded RNA-1. Acute hepatitis was associated with the EBV infection. The whole-blood EBV DNA levels were high and above 1.0 × 107 copies/mL. After immunosuppressive and antiviral therapies, EBV DNA levels lowered. However, she had to receive bone marrow transplantation because of her EBV-HLH. As the number of lymphocytes increased in the post-transplantation period, EBV DNA levels gradually increased again. The simultaneous detection of CMV DNA was more sensitive than the CMV antigenemia test that is often used to diagnose CMV infections. Unfortunately, the patient died due to a fungal infection. Observing EBV DNA levels closely with real-time quantitative PCR methods is helpful for evaluating the changes in the clinical course.

Monitoring twenty-six chronic myeloid leukemia patients by BCR-ABL mRNA level in bone marrow:a single hospital experience.

Chronic myeloid leukemia (CML) is caused by the BCR-ABL oncogene. The Philadelphia chromosome (Ph) from a reciprocal translocation, t(9;22) (q34;q11) causes a fusion gene, BCR-ABL, that encodes a constitutively active tyrosine kinase. Treatment of CML by imatinib is effective to control the tyrosyl phosphorylation of the protein related to the cell signaling. BCR-ABL mRNA is overexpressed in the minimal residual disease (MRD), known as an early sign of relapse. Between December 2005 and June 2008, we measured BCR-ABL mRNA levels in the bone marrow (BM) from patients by quantitative real-time polymerase chain reaction (RQ-PCR) in Aomori Prefectural Central Hospital. Eighty-six samples from 26 patients were collected. Among the 26 CML patients, 11 patients (42%) were in the pretreatment group. Seven (64%) of the 11 patients achieved complete molecular response (CMR). In the post-treatment group consisting of the remaining 15 patients, 9 (60%) patients achieved CMR. The patients receiving imatinib at a dose over 300 mg per day required 13 (6-77) months [median (range)] to achieve CMR. On the other hand, the patients receiving a dose below 300 mg per day required 29.5 (11-84) months [median (range)]. When BCR-ABL mRNA was detected during the treatment course of patients with CMR, careful observation of BCR-ABL mRNA was useful for tracking the clinical course of patients. In conclusion, the BCR-ABL mRNA level was useful for monitoring the clinical course in 26 patients with CML.