Masanari Niwa

Dr. Masanari Niwa


Research Focus & Metrics

Academic Career Length

5Years (2022-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

View All Publications
31 January 2023 in Cancers
Verified
Journal Article
Open access
PDF file
NKNozomi Kita
Nozomi Kita
Natsuo TomitaNatsuo Tomita
Natsuo Tomita
TTTaiki Takaoka
Taiki Takaoka
SSSudo Sudo
Sudo Sudo
YTYusuke Tsuzuki
Yusuke Tsuzuki
AHAkio Hiwatashi
Akio Hiwatashi
We compared recurrence patterns between adenocarcinoma (ADC) and squamous cell carcinoma (SCC) after stereotactic body radiotherapy (SBRT) for early-stage lung cancer. Patients with ADC and SCC histology, who were treated with SBRT for clinical stage IA1-IIA lung cancer at our institution, were included in the analysis. The rates of disease-free survival (DFS), overall survival (OS), local recurrence (LR), lymph node metastasis (LNM), and distant metastasis (DM) were calculated using the Kaplan–Meier method or the cumulative incidence function. Among the 204 patients analyzed, 138 and 66 were in the ADC and SCC groups, respectively. The median follow-up period was 60 months. The five-year DFS and OS rates were 57% vs. 41% and 69% vs. 48% in the ADC and SCC groups, respectively (p = 0.015 and 0.019, respectively). In the multivariate analysis, the histological type was not associated with DFS or OS. Five-year LR, LNM, and DM rates were 10% vs. 24%, 12% vs. 20%, and 25% vs. 27% in the ADC and SCC groups, respectively (p = 0.0067, 0.074, and 0.67, respectively). The multivariate analysis identified the histological type of SCC as an independent factor for LR (hazard ratio, 2.41; 95% confidence interval, 1.21–4.77; p = 0.012). The present results suggest that the risk of LR after SBRT is higher for SCC than for ADC.

29 April 2025 in Cancers
Verified
Journal Article
Open access
PDF file
MNMasanari Niwa
Masanari Niwa
Natsuo TomitaNatsuo Tomita
Natsuo Tomita
HIHiromichi Ishiyama
Hiromichi Ishiyama
HKHijiri Kaneko
Hijiri Kaneko
YOYukihiko Oshima
Yukihiko Oshima
AHAkio Hiwatashi
Akio Hiwatashi
Background: Extramammary Paget’s disease (EMPD) is a rare cutaneous carcinoma that typically affects the elderly and is frequently observed in genital and perianal regions. We analyzed the outcomes and prognostic factors for EMPD after radiation therapy (RT). Methods: We analyzed data from 81 patients with non-metastatic EMPD who received either RT alone or in combination with surgery and/or chemotherapy. The median radiation dose was 56 Gy in 28 fractions. Local control (LC), progression-free survival (PFS), and overall survival (OS) rates were calculated using the Kaplan–Meier method. Multivariate analyses were performed using the Cox proportional hazards model. Late adverse events were evaluated by NCI-CTCAE version 5.0. Results: The median age was 78 years, and the median follow-up period was 36 months. The three-year LC, PFS, and OS rates were 75%, 52%, and 80%, respectively. Multivariate analyses identified the presence of lymph node (LN) metastasis, the absence of surgery, and the omission of elective nodal irradiation (i.e., local irradiation only) as significant factors for unfavorable LC (p = 0.01, 0.02, and 0.006) and PFS (p = 0.001, 0.04, and 0.03). LN metastasis was also a significant factor for unfavorable OS (p = 0.005). One patient developed grade 2 skin infection, and another developed grade 3 lymphedema; no grade 4 or higher toxicity was observed. Conclusions: The present results revealed prognostic factors for EMPD after RT and suggest that the absence of surgery and omission of elective nodal irradiation worsened outcomes. A prospective study is needed to establish an optimal treatment strategy for this rare malignancy, which is common in the elderly.

20 July 2023 in Cancers
Verified
Journal Article
Open access
PDF file
MNMasanari Niwa
Masanari Niwa
Natsuo TomitaNatsuo Tomita
Natsuo Tomita
TTTaiki Takaoka
Taiki Takaoka
HTHirota Takano
Hirota Takano
CMChiyoko Makita
Chiyoko Makita
AHAkio Hiwatashi
Akio Hiwatashi
Angiosarcoma of the scalp and face (ASF) is a rare, aggressive tumor often treated with multimodal therapy, including radiation therapy (RT). This study assessed RT outcomes for ASF and identified prognostic factors. Data from 68 non-metastatic ASF patients undergoing RT with or without other therapies were analyzed. Median radiation dose was 66 Gy in 33 fractions (interquartile range (IQR) 60–70 Gy in 28–35 fractions). Local control (LC), progression-free survival (PFS), and overall survival (OS) rates were calculated using Kaplan–Meier analysis. Multivariate analyses and adverse event evaluation were conducted. Median patient age was 75 years (IQR 71–80 years), with a median follow-up of 17 months (IQR 11–42 months). One-/three-year LC rates were 57/37%, PFS rates were 44/22%, and OS rates were 81/44%. Multivariate analyses showed that an equivalent dose in a 2 Gy fraction (EQD2) >66 Gy correlated with improved LC (HR 2.35, 95% CI 1.03–5.32, p = 0.041). Combining chemotherapy (HR 2.43, 95% CI 1.08–5.46, p = 0.032) or surgery (HR 2.41, 95% CI 1.03–5.59, p = 0.041) improved PFS. No factors influenced OS. Late grade 3+ toxicities occurred in 1%, with one patient developing a grade 4 skin ulcer. These findings suggest that EQD2 > 66 Gy and combining chemotherapy or surgery can enhance LC or PFS in ASF. Further prospective studies are needed to determine the optimal treatment strategy for this rare malignancy, particularly in elderly patients.

5 December 2022 in BMC Cancer
Verified
Journal Article
Open access
PDF file
Natsuo TomitaNatsuo Tomita
Natsuo Tomita
HIHiromichi Ishiyama
Hiromichi Ishiyama
MCMakita Chiyoko
Makita Chiyoko
YOYukihiko Ohshima
Yukihiko Ohshima
ANAiko Nagai
Aiko Nagai
AHAkio Hiwatashi
Akio Hiwatashi
Background: Radiobiological daily changes within tumors are considered to be quite different between stereotactic radiotherapy (SRT) (e.g., 50 Gy in 4 fractions) and conventional radiotherapy (e.g., 60 Gy in 30 fractions). We aim to assess the optimal interval of irradiation in SRT and compare outcomes of daily irradiation with irradiation at two- to three-day intervals in SRT for patients with one to five brain metastases (BM). Methods: This study is conducted as a multicenter open-label randomized phase II trial. Patients aged 20 or older with one to five BM, less than 3.0 cm diameter, and Karnofsky Performance Status ≥70 are eligible. A total of 70 eligible patients will be enrolled. After stratifying by the number of BMs (1, 2 vs. 3–5) and diameter of the largest tumor (< 2 cm vs. ≥ 2 cm), we randomly assigned patients (1:1) to receive daily irradiation (Arm 1), or irradiation at two- to three-day intervals (Arm 2). Both arms are performed with total dose of 27-30 Gy in 3 fractions. The primary endpoint is an intracranial local control rate, defined as intracranial local control at initially treated sites. We use a randomized phase II screening design with a two-sided α of 0∙20. The phase II trial is positive with p < 0.20. All analyses are intention to treat. This study is registered with the UMIN-clinical trials registry, number UMIN000048728. Discussion: This study will provide an assessment of the impact of SRT interval on local control, survival, and toxicity for patients with 1–5 BM. The trial is ongoing and is recruiting now. Trial registration: UMIN000048728. Date of registration: August 23, 2022. https://center6.umin.ac.jp/cgi-bin/ctr/ctr_view_reg.cgi?recptno=R000055515.

30 June 2022 in The Kurume Medical Journal
Verified
Journal Article
Open access
PDF file
MNMasanari Niwa
Masanari Niwa
NTNatsuo Tomita
Natsuo Tomita
AMAkifumi Miyakawa
Akifumi Miyakawa
SAShiho Ayakawa
Shiho Ayakawa
NTNatsuko Takama
Natsuko Takama
YSYuta Shibamoto
Yuta Shibamoto
Summary: Introduction: Radiation therapy (RT) for choroidal metastasis (CM) aims to preserve vision and achieve local control (LC), thereby maintaining quality of life. The present study reports the clinical outcomes of RT for CM and reviews the literature. Methods: We retrospectively collected data on 11 patients with CM; their primary tumors were breast cancer (n=3), lung cancer (n=3), leukemia (n=2), lymphoma (n=2), and gastric cancer (n=1). Four patients had bilateral CM. The median radiation dose was 39 Gy in 13 fractions (range, 20–50 Gy in 10–25 fractions). We investigated changes in visual acuity, tumor responses, morbidities, LC, and overall survival (OS). A systematic review of literature published between 1990 and 2020 was performed using the PubMed database. Results: One, 1, and 6 patients had improved, stabilized, and worse visual acuity, respectively (data missing for 3 patients). Nevertheless, eight patients considered their visual acuity to have improved or remained the same after RT. Among 15 lesions in 11 patients, complete and partial responses were observed in 2 and 6, respectively (data missing for 7 lesions in 4 patients). Three-year LC and OS rates were 100 and 32%, respectively. Grade ≥ 3 morbidities were not observed. In the literature review, the most common primary cancer was breast cancer followed by lung cancer. Improvements in or the stabilization of visual acuity was observed in 80% of patients (range, 47-100), and the median survival time was 11 months (range, 4.9-23). Conclusion: RT is an efficient and safe palliative treatment for CM without severe toxicity.

14 April 2026 in Cancers
Verified
Journal Article
Open access
PDF file
Natsuo TomitaNatsuo Tomita
Natsuo Tomita
DKDaisuke Kawakita
Daisuke Kawakita
TMTakuma Matoba
Takuma Matoba
KMKiyoshi Minohara
Kiyoshi Minohara
SISho Iwaki
Sho Iwaki
AHAkio Hiwatashi
Akio Hiwatashi
Objectives: This study investigates the association of pretreatment underweight, sarcopenia, and cancer cachexia with survival outcome in hypopharyngeal cancer (HPC) radiotherapy. Methods: This retrospective observational study analyzed 167 patients with newly diagnosed HPC treated with definitive radiotherapy. The definitions of underweight, sarcopenia, and cancer cachexia are based on the international consensus of the European Palliative Care Research Collaborative. Underweight and sarcopenia were analyzed in all 167 patients, while cachexia analyses were restricted to the 117 patients for whom pretreatment weight-loss data were available. Survival outcomes were estimated using the Kaplan–Meier method and compared using the log-rank test, and subsequently analyzed using multivariate Cox proportional hazards models. Results: The median follow-up period was 28 months. Cachexia analyses were restricted to the 117 patients for whom pretreatment weight-loss data were available; of these, 45 (38%) met criteria for cancer cachexia. Patients with underweight (n = 76, 46%) or cancer cachexia had significantly lower locoregional control, disease-free survival, and overall survival compared to those not underweight and without cachexia, respectively, whereas there was no difference in any outcome between patients with sarcopenia (n = 54, 32%) and those without. Given the definitional overlap among underweight, sarcopenia, and cachexia, these three variables were entered into the multivariate analysis separately—which included age, sex, performance status, double cancer, T-classification, N-classification, chemotherapy administration, treatment era, and radiation dose—confirming that underweight and cancer cachexia remained independently associated with worse LRC, DFS, and OS. In the fully adjusted multivariate Cox proportional hazards models, the hazard ratios for mortality risk were 1.9 (95% confidence interval [CI], 1.1–3.4; p = 0.030) and 2.0 (95% CI, 1.1–3.8; p = 0.032) for patients with underweight or cancer cachexia, respectively. Conclusions: Pretreatment underweight and cancer cachexia negatively impact survival outcomes, including locoregional control, in HPC radiotherapy. Prospective studies with standardized nutritional assessment protocols, pre-specified intervention arms, and sufficient sample sizes are essential to validate these findings and to establish the clinical benefit of pre-treatment nutritional optimization in this patient population.