Ryuta Sasamoto
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The organizations/institutes from the scholar's latest article
Previous Organizations / Institutes
The organizations / institutes from the scholar's other articles in the past ten years
Ryuta Sasamoto has a total of 42 co-authors. Here are the top co-authors by number of shared publications:
- Eisuke Abe
Niigata University Graduate School of Medical and Dental Sciences
3 shared publications - Hidefumi Aoyama
Department of Radiation Oncology, Faculty of Medicine, Hokkaido University , Kita 15, Nishi 7, Kita-ku, Sapporo, 060-8638
2 shared publications - Motoki Kaidu
Department of Radiology and Radiation Oncology, Graduate School of Medical and Dental Sciences, Niigata University, Niigata 951-8514, Japan
2 shared publications Atsushi Ohta
Department of Radiology and Radiation Oncology, Niigata University Graduate School of Medical and Dental Sciences, 1-757 Asahimachi-dori, Chuo-ku, Niigata 951-8510, Japan
1 shared publication- Atsushi Ohta
Departments of Radiation Oncology, Niigata University Medical and Dental Hospital, Asahimachi-dori, Chuo-ku, Niigata, Japan.
1 shared publication - Fumio Ayukawa
Departments of Radiation Oncology, Niigata University Medical and Dental Hospital, Asahimachi-dori, Chuo-ku, Niigata, Japan.
1 shared publication
Latest Publications
- Open Access
- 27 July 2025
- Published by Japanese Society for Spine Surgery and Related Research in Spine Surgery and Related Research
- Vol. 9 (4) , 416-425
Relationship between Health-Related Quality of Life and Sagittal Whole-Body Alignment, Standing Balance, and Skeletal Muscle Mass
Introduction: Impaired standing alignment and postural instability diminish health-related quality of life (HRQOL). Reduced trunk muscle mass is correlated with worsened spinal alignment and HRQOL in patients with spinal disease. However, the interplay among standing balance, whole-body alignment, muscle mass, and HRQOL remains unclear. This study aimed to elucidate this relationship.Methods: This study evaluated the influence of whole-body alignment, standing balance, skeletal muscle mass (SMM), aging, and sex on HRQOL in healthy volunteers (HV; men/women: 37/63, median age: 45), patients with lumbar degeneration (LD; men/women: 100/100, median age: 65), and patients with spinal deformity (SD; men/women: 16/84, median age: 71). HRQOL was assessed using the Scoliosis Research Society-22 (SRS-22r). Whole-body alignment and standing balance were measured using EOS Imaging combined with simultaneous force plate measurements. SMM was measured using a medical body composition analyzer. Based on univariate analysis and multicollinearity, 10 selected parameters were used in multivariate logistic regression analysis to identify factors affecting SRS-22r.Results: The SRS-22r score was significantly higher in the HV group than in the LD and SD groups; however, there were no significant differences between men and women. The whole-body alignment and standing balance were better in the HV group, followed by the LD and SD groups. The total-body SMM (SMM.total) of men was significantly lower in the LD and SD groups than in the HV group. In females, the SMM.total was significantly lower in the SD group than in the HV and LD groups. However, trunk SMM did not significantly differ among the three groups. Based on the multivariate analyses, diagnosis, body mass index (BMI), SMM.total, lumbar lordosis (LL), and T1 pelvic angle (TPA) were correlated with the SRS-22r score.Conclusions: HRQOL was negatively affected by spinal disease, as well as by higher BMI, lower SMM.total, and sagittal malalignment (smaller LL and greater TPA).
- 27 July 2025
- Published by Japanese Society for Spine Surgery and Related Research in Spine Surgery and Related Research
- Vol. 9 (4) , 416-425
Open AccessRelationship between Health-Related Quality of Life and Sagittal Whole-Body Alignment, Standing Balance, and Skeletal Muscle Mass
Introduction: Impaired standing alignment and postural instability diminish health-related quality of life (HRQOL). Reduced trunk muscle mass is correlated with worsened spinal alignment and HRQOL in patients with spinal disease. However, the interplay among standing balance, whole-body alignment, muscle mass, and HRQOL remains unclear. This study aimed to elucidate this relationship.Methods: This study evaluated the influence of whole-body alignment, standing balance, skeletal muscle mass (SMM), aging, and sex on HRQOL in healthy volunteers (HV; men/women: 37/63, median age: 45), patients with lumbar degeneration (LD; men/women: 100/100, median age: 65), and patients with spinal deformity (SD; men/women: 16/84, median age: 71). HRQOL was assessed using the Scoliosis Research Society-22 (SRS-22r). Whole-body alignment and standing balance were measured using EOS Imaging combined with simultaneous force plate measurements. SMM was measured using a medical body composition analyzer. Based on univariate analysis and multicollinearity, 10 selected parameters were used in multivariate logistic regression analysis to identify factors affecting SRS-22r.Results: The SRS-22r score was significantly higher in the HV group than in the LD and SD groups; however, there were no significant differences between men and women. The whole-body alignment and standing balance were better in the HV group, followed by the LD and SD groups. The total-body SMM (SMM.total) of men was significantly lower in the LD and SD groups than in the HV group. In females, the SMM.total was significantly lower in the SD group than in the HV and LD groups. However, trunk SMM did not significantly differ among the three groups. Based on the multivariate analyses, diagnosis, body mass index (BMI), SMM.total, lumbar lordosis (LL), and T1 pelvic angle (TPA) were correlated with the SRS-22r score.Conclusions: HRQOL was negatively affected by spinal disease, as well as by higher BMI, lower SMM.total, and sagittal malalignment (smaller LL and greater TPA).
- 20 December 2022
- Published by Springer Nature in Japanese Journal of Radiology
- Vol. 41 (5) , 561-568
Relationship between absorbed dose and changes in liver volume after chemoradiotherapy for esophageal cancer
Purpose The liver is the largest organ in the abdomen and is often irradiated in radiotherapy for non-hepatic malignancies. As most of the studies on changes in liver volume are on hepatocellular carcinoma based on liver dysfunction, there are few studies on healthy liver. In this study, we investigated the relationship between absorbed dose and changes in liver volume after chemoradiotherapy for esophageal cancer in patients without apparent pre-treatment liver dysfunction. Materials and methods Liver volume was compared between pre-treatment, acute (< 4 months) and late post-treatment (≥ 4 and < 13 months) phases in 12 patients using abdominal plain CT images. Volume changes were evaluated separately for the right and left lobes. We investigated the relationship between the volume change and VxGy (percentage of volume received x Gy or more dose). In addition, volume change for each absorbed dose was investigated using deformable image registration. Results The volume of the left lobe showed a significant decrease between pre-treatment and acute post-treatment phases (p < 0.001), while the volume of right lobe and between acute and late post-treatment phase of left lobe did not. The mean value of the volume reduction rate of the left lobe was 51.1% and equivalent to the mean value of V30Gy. As a result of the volume change for each absorbed dose, the volume reduction rate increased as the absorbed dose increased, and a significant volume loss was observed at doses above 11 Gy. Conclusion Volume of the liver significantly decreased only in the acute phase after chemoradiotherapy for esophageal cancer. The tolerable dose for a healthy liver is generally considered to be 30 Gy, but attention should be paid to lower doses to avoid radiation-induced liver injury.
- 20 December 2022
- Published by Springer Nature in Japanese Journal of Radiology
- Vol. 41 (5) , 561-568
Relationship between absorbed dose and changes in liver volume after chemoradiotherapy for esophageal cancer
Purpose The liver is the largest organ in the abdomen and is often irradiated in radiotherapy for non-hepatic malignancies. As most of the studies on changes in liver volume are on hepatocellular carcinoma based on liver dysfunction, there are few studies on healthy liver. In this study, we investigated the relationship between absorbed dose and changes in liver volume after chemoradiotherapy for esophageal cancer in patients without apparent pre-treatment liver dysfunction. Materials and methods Liver volume was compared between pre-treatment, acute (< 4 months) and late post-treatment (≥ 4 and < 13 months) phases in 12 patients using abdominal plain CT images. Volume changes were evaluated separately for the right and left lobes. We investigated the relationship between the volume change and VxGy (percentage of volume received x Gy or more dose). In addition, volume change for each absorbed dose was investigated using deformable image registration. Results The volume of the left lobe showed a significant decrease between pre-treatment and acute post-treatment phases (p < 0.001), while the volume of right lobe and between acute and late post-treatment phase of left lobe did not. The mean value of the volume reduction rate of the left lobe was 51.1% and equivalent to the mean value of V30Gy. As a result of the volume change for each absorbed dose, the volume reduction rate increased as the absorbed dose increased, and a significant volume loss was observed at doses above 11 Gy. Conclusion Volume of the liver significantly decreased only in the acute phase after chemoradiotherapy for esophageal cancer. The tolerable dose for a healthy liver is generally considered to be 30 Gy, but attention should be paid to lower doses to avoid radiation-induced liver injury.
- Open Access
- 5 April 2021
- Published by Oxford University Press (OUP) in Journal of Radiation Research
- Vol. 62 (3) , 525-532
A comparative study of high-dose-rate brachytherapy boost combined with external beam radiation therapy versus external beam radiation therapy alone for high-risk prostate cancer
We aimed to compare the outcomes of high-dose-rate brachytherapy (HDR-BT) boost and external beam radiation therapy (EBRT) alone for high-risk prostate cancer. This was a single-center, retrospective and observational study. Consecutive patients who underwent initial radical treatment by HDR-BT boost or EBRT alone from June 2009 to May 2016 at the Niigata University Medical and Dental Hospital, Japan were included. A total of 96 patients underwent HDR-BT boost, and 61 underwent EBRT alone. The prescription dose of HDR-BT boost was set to 18 Gy twice a day with EBRT 39 Gy/13 fractions. The dose for EBRT alone was mostly 70 Gy/28 fractions. The high-risk group received >6 months of prior androgen deprivation therapy. Overall survival, biochemical-free survival, local control and distant metastasis-free survival rates at 5 years were analyzed. The incidence of urological and gastrointestinal late adverse events of Grade 2 and above was also summarized. In the National Comprehensive Cancer Network (NCCN) high-risk calssification, HDR-BT boost had a significantly higher biochemical-free survival rate at 5 years (98.9% versus 90.7%, P = 0.04). Urethral strictures were more common in the HDR-BT boost group. We will continuously observe the progress of the study patients and determine the longer term results.
- 5 April 2021
- Published by Oxford University Press (OUP) in Journal of Radiation Research
- Vol. 62 (3) , 525-532
Open AccessA comparative study of high-dose-rate brachytherapy boost combined with external beam radiation therapy versus external beam radiation therapy alone for high-risk prostate cancer
We aimed to compare the outcomes of high-dose-rate brachytherapy (HDR-BT) boost and external beam radiation therapy (EBRT) alone for high-risk prostate cancer. This was a single-center, retrospective and observational study. Consecutive patients who underwent initial radical treatment by HDR-BT boost or EBRT alone from June 2009 to May 2016 at the Niigata University Medical and Dental Hospital, Japan were included. A total of 96 patients underwent HDR-BT boost, and 61 underwent EBRT alone. The prescription dose of HDR-BT boost was set to 18 Gy twice a day with EBRT 39 Gy/13 fractions. The dose for EBRT alone was mostly 70 Gy/28 fractions. The high-risk group received >6 months of prior androgen deprivation therapy. Overall survival, biochemical-free survival, local control and distant metastasis-free survival rates at 5 years were analyzed. The incidence of urological and gastrointestinal late adverse events of Grade 2 and above was also summarized. In the National Comprehensive Cancer Network (NCCN) high-risk calssification, HDR-BT boost had a significantly higher biochemical-free survival rate at 5 years (98.9% versus 90.7%, P = 0.04). Urethral strictures were more common in the HDR-BT boost group. We will continuously observe the progress of the study patients and determine the longer term results.
- Open Access
- 31 January 2015
- Published by Springer Nature in Radiation Oncology
- Vol. 10 (1) , 31
The effectiveness of endoscopic submucosal dissection followed by chemoradiotherapy for superficial esophageal cancer
To evaluate the risks and benefits of endoscopic submucosal dissection (ESD) in addition to chemoradiotherapy (CRT) for the treatment of superficial esophageal squamous cell carcinoma (SESCC). We retrospectively reviewed the treatment outcomes of 47 patients with SESCC treated between October 2000 and December 2011. Sixteen patients with invasion into the submucosal layer (T1b) or the muscularis mucosa (m3) with positive vascular invasion were treated with CRT after ESD (ESD-CRT group). The lymph node area was irradiated to a total dose of 40–44 Gy and a boost radiation was administered if PET-positive lymph nodes or positive margins were observed. The remaining 31 patients received definitive CRT only (dCRT group). The radiation field was significantly larger in the ESD-CRT group; the “long T” was used in 11 patients (35.4%) in the dCRT group and 15 (93.7%) in the ESD-CRT group (p = 0.0001). The total radiation dose was smaller in the ESD-CRT group; 40 Gy was used in 10 patients (62.5%) in the ESD-CRT group and all but one patient in the dCRT group received ≥60 Gy (p = 0.00001). The 3-year overall survival rates in the dCRT and ESD-CRT groups were 63.2% and 90.0% respectively (p = 0.118). Recurrence developed in nine patients (29.0%) in the dCRT group and one (6.3%) in the ESD-CRT group. Local recurrence was observed in six patients (19%) in the dCRT group and none in the ESD-CRT-group (p = 0.029). Pericardial effusion (≥Grade 3) occurred in three patients (9.7%) in the dCRT group and none in the ESD-CRT group. ESD followed by CRT is an effective and safe approach for SESCC at m3 or T1b. This combination of ESD and CRT improves the local control rate, and it could decrease the number of cardiac toxicities due to a radiation-dose reduction relative to CRT alone.
- 31 January 2015
- Published by Springer Nature in Radiation Oncology
- Vol. 10 (1) , 31
Open AccessThe effectiveness of endoscopic submucosal dissection followed by chemoradiotherapy for superficial esophageal cancer
To evaluate the risks and benefits of endoscopic submucosal dissection (ESD) in addition to chemoradiotherapy (CRT) for the treatment of superficial esophageal squamous cell carcinoma (SESCC). We retrospectively reviewed the treatment outcomes of 47 patients with SESCC treated between October 2000 and December 2011. Sixteen patients with invasion into the submucosal layer (T1b) or the muscularis mucosa (m3) with positive vascular invasion were treated with CRT after ESD (ESD-CRT group). The lymph node area was irradiated to a total dose of 40–44 Gy and a boost radiation was administered if PET-positive lymph nodes or positive margins were observed. The remaining 31 patients received definitive CRT only (dCRT group). The radiation field was significantly larger in the ESD-CRT group; the “long T” was used in 11 patients (35.4%) in the dCRT group and 15 (93.7%) in the ESD-CRT group (p = 0.0001). The total radiation dose was smaller in the ESD-CRT group; 40 Gy was used in 10 patients (62.5%) in the ESD-CRT group and all but one patient in the dCRT group received ≥60 Gy (p = 0.00001). The 3-year overall survival rates in the dCRT and ESD-CRT groups were 63.2% and 90.0% respectively (p = 0.118). Recurrence developed in nine patients (29.0%) in the dCRT group and one (6.3%) in the ESD-CRT group. Local recurrence was observed in six patients (19%) in the dCRT group and none in the ESD-CRT-group (p = 0.029). Pericardial effusion (≥Grade 3) occurred in three patients (9.7%) in the dCRT group and none in the ESD-CRT group. ESD followed by CRT is an effective and safe approach for SESCC at m3 or T1b. This combination of ESD and CRT improves the local control rate, and it could decrease the number of cardiac toxicities due to a radiation-dose reduction relative to CRT alone.
- 25 May 2011
- Published by Springer Nature in International Journal of Clinical Oncology
- Vol. 17 (1) , 48-54
Clinical practice and outcome of radiotherapy for esophageal cancer between 1999 and 2003: the Japanese Radiation Oncology Study Group (JROSG) Survey
To determine the clinical results of radiotherapy (RT) for esophageal cancer in Japan. A questionnaire-based survey was conducted for esophageal cancer treated by definitive RT between 1999 and 2003. Clinical results of definitive RT for patients were collected from 9 major institutions. Only patients with good performance status (PS 0–2) who received a total dose of 50 Gy or more were included. Patients were classified into three groups: (A) stage I, (B) resectable stages II–III, (C) unresectable stages III–IVA. For group A, all patients treated by RT alone or chemo-radiotherapy (CRT) were included. For groups B and C, only those treated by CRT were included. In total, 167 patients were included in group A, 239 in group B, and 244 in group C. Approximately half of the patients in group A were treated by CRT. The median total RT dose ranged from 60 to 66 Gy. The median and range of the 5-year overall survival rates were 56% (48–83%) for group A, 29% (12–52%) for group B, and 19% (0–31%) for group C, respectively. A wide disparity in overall survival rates was noted among the institutions. A significant correlation between the number of patients treated per year and the 5-year overall survival rate was noted for groups B and C (both p < 0.05). Although the overall survival rates for stage I esophageal cancer were excellent, a significant disparity in survival rates was noted among the institutions for stage II–IVA tumors treated by CRT.
- 25 May 2011
- Published by Springer Nature in International Journal of Clinical Oncology
- Vol. 17 (1) , 48-54
Clinical practice and outcome of radiotherapy for esophageal cancer between 1999 and 2003: the Japanese Radiation Oncology Study Group (JROSG) Survey
To determine the clinical results of radiotherapy (RT) for esophageal cancer in Japan. A questionnaire-based survey was conducted for esophageal cancer treated by definitive RT between 1999 and 2003. Clinical results of definitive RT for patients were collected from 9 major institutions. Only patients with good performance status (PS 0–2) who received a total dose of 50 Gy or more were included. Patients were classified into three groups: (A) stage I, (B) resectable stages II–III, (C) unresectable stages III–IVA. For group A, all patients treated by RT alone or chemo-radiotherapy (CRT) were included. For groups B and C, only those treated by CRT were included. In total, 167 patients were included in group A, 239 in group B, and 244 in group C. Approximately half of the patients in group A were treated by CRT. The median total RT dose ranged from 60 to 66 Gy. The median and range of the 5-year overall survival rates were 56% (48–83%) for group A, 29% (12–52%) for group B, and 19% (0–31%) for group C, respectively. A wide disparity in overall survival rates was noted among the institutions. A significant correlation between the number of patients treated per year and the 5-year overall survival rate was noted for groups B and C (both p < 0.05). Although the overall survival rates for stage I esophageal cancer were excellent, a significant disparity in survival rates was noted among the institutions for stage II–IVA tumors treated by CRT.
- 22 January 2010
- Published by Springer Nature in International Journal of Clinical Oncology
- Vol. 15 (1) , 104-108
Elevation of serum carcinoembryonic antigen level in a patient with hypothyroidism after radiation therapy for cervical esophageal cancer
We report the case of a 51-year-old woman who showed elevation of serum carcinoembryonic antigen (CEA) level 14 months after chemoradiation therapy for her cervical esophageal cancer. Close examination demonstrated that the patient was suffering from hypothyroidism probably due to the chemoradiation therapy. The serum CEA level decreased after starting supplementary treatment with oral levothyroxine. The exact mechanism underlying the elevated level of CEA observed in a patient with hypothyroidism is unclear. However, we should be aware of the possibility of transient elevation of CEA affected by thyroid function in patients after radiation therapy for head and neck cancer.
- 22 January 2010
- Published by Springer Nature in International Journal of Clinical Oncology
- Vol. 15 (1) , 104-108
Elevation of serum carcinoembryonic antigen level in a patient with hypothyroidism after radiation therapy for cervical esophageal cancer
We report the case of a 51-year-old woman who showed elevation of serum carcinoembryonic antigen (CEA) level 14 months after chemoradiation therapy for her cervical esophageal cancer. Close examination demonstrated that the patient was suffering from hypothyroidism probably due to the chemoradiation therapy. The serum CEA level decreased after starting supplementary treatment with oral levothyroxine. The exact mechanism underlying the elevated level of CEA observed in a patient with hypothyroidism is unclear. However, we should be aware of the possibility of transient elevation of CEA affected by thyroid function in patients after radiation therapy for head and neck cancer.