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Background and purpose We aimed to determine the risk factors for radiation-induced brain injury (RIBI 1 ) after carbon ion radiotherapy (CIRT) to predict their probabilities in long-term survivors. Materials and methods We evaluated 104 patients with head, neck, and skull base tumors who underwent CIRT in a regimen of 32 fractions and were followed up for at least 24 months. RIBI was assessed using the Common Terminology Criteria for Adverse Events. Results The median follow-up period was 45.5 months; 19 (18.3 %) patients developed grade ≥2 RIBI. The maximal absolute dose covering 5 mL of the brain (D5ml) was the only significant risk factor for grade ≥2 RIBI in the multivariate logistic regression analysis (p = 0.001). The tolerance doses of D5ml for the 5% and 50% probabilities of developing grade ≥2 RIBI were estimated to be 55.4 Gy (relative biological effectiveness [RBE]) and 68.4 Gy (RBE) by a logistic model, respectively. Conclusion D5ml was most significantly associated with grade ≥2 RIBI and may enable the prediction of its probability.

We attempted to re-evaluate the efficacy of prophylactic cranial irradiation (PCI) in limited-stage small cell lung cancer (LS-SCLC) with more recent data. A total of 179 patients with LS-SCLC received radical thoracic radiotherapy and chemotherapy at our institution between 1998 and 2018. One hundred twenty-eight patients who achieved complete response (CR), good partial response (PR), and PR without progression for at least for one year after initial therapy were enrolled in this study. These patients were divided into a PCI group (group A, n = 43), and a non-PCI group (group B, n = 85). Survival outcomes were retrospectively evaluated. Because several background factors differed significantly between groups A and B, propensity score (PS) matching was performed as 1:1 match of the two groups. Finally, we analyzed 64 patients (group A/B = 32/32). Median follow-up periods were 53 and 31 months in groups A and B, respectively. There were no significant differences between the groups’ backgrounds. Two-year overall survival (OS) rates were 77% in group A and 62% in group B (p = 0.224). Two-year brain metastasis free survival (BMFS) rates were 85% in group A and 57% in group B (p = 0.008). The number of patients who underwent a brain imaging test for confirmation of no brain metastasis (BM) after radical thoracic radiotherapy and chemotherapy (before PCI) was 84 (group A/B = 32/52). A PS matched analysis for cases of pre-PCI brain imaging group, two-year OS rates for group A/B were 73/59% (p = 0.446). Two-year BMFS rates for group A/B were 91/52% (p = 0.021). Retrospectively, PS matched analysis revealed that adding PCI to LS-SCLC patients who achieved good thoracic control significantly improved BMFS, but OS did not improve.

This study aimed to determine the maximum tolerance dose (MTD) and to estimate the recommended dose (RD) of concomitant S-1 with carbon-ion radiotherapy (RT) for sinonasal squamous cell carcinoma (SCC). Nine patients with sinonasal SCC received carbon-ion RT with escalating doses of S-1 according to phase I methods. Doses of 40, 60 and 80 mg/m2/day were administered twice daily in dose levels 1, 2 and 3, respectively, from days 1 to 14 and 22 to 35. Carbon-ion RT was administered at a dose of 70.4 Gy (relative biological effectiveness) in 32 fractions, 5 days a week. Two patients developed grade 3 acute dermatitis. However, none developed dose-limiting toxicities. Therefore, the MTD of S-1 could not be determined; the RD was estimated to be 80 mg/m2/day with concurrent carbon-ion RT. Partial response and stable disease were noted in 5 and 4 patients, respectively. The 2-year overall survival and local control rates were 56 and 74%, respectively. Overall, 2 patients developed ≥grade 3 late toxicities; among them, 1 patient developed grade 3 cataract and the other developed grade 4 cataract, optic nerve disorder and hearing impairment. To the best of our knowledge, this phase I study is the first clinical trial to evaluate concomitant S-1 with carbon-ion RT for sinonasal SCC. The MTD of S-1 could not be determined, and the RD was estimated to be 80 mg/m2/day. This study demonstrated a manageable safety profile for this combination. The observed outcomes may facilitate further evaluation of this novel therapy.

Background: The outcomes of chemotherapy for patients with perihilar cholangiocarcinoma (PHC) are unsatisfactory, and photon therapy for unresectable PHC reportedly results in improved outcomes. Proton beam therapy (PBT) can be a treatment option for these patients; however, the role of PBT in these patients is poorly defined as PHC is rare. Herein, we evaluated the efficacy and safety of PBT for unresectable PHC.Methods: This observational retrospective cohort study conducted at a single institution included patients with unresectable PHC who received definitive PBT. Patients who had nodal metastasis at presentation or those who underwent surgery or other radiation therapies before PBT were excluded. To compare different dose fractionations, biologically equivalent doses with α/β=10 [BED10] were calculated.Results: Overall, 26 patients were eligible. The commonly prescribed doses were 67.5 Gy (relative biological effectiveness [RBE]) in 25 fractions or 70.2 Gy (RBE) in 26 fractions. The median follow-up period was 19.4 months (range, 4.2-137.4 months). The Kaplan–Meier estimates of the 1-, 2-, and 5-year overall survival (OS) rates were 72.9%, 47.7%, and 17.4%, respectively, and the median survival time was 23.7 months. The multivariate analysis demonstrated that Child–Pugh classification B was a significant prognostic factor for unfavorable OS (hazard ratio [HR] 4.92; p=0.009) and that a mean gross tumor volume dose of ≥79.2 Gy (RBE) [BED10] was a significant prognostic factor for favorable OS (HR 0.19; p=0.025). Grade ≥3 late adverse events were observed in seven patients (26.9%).Conclusions: We demonstrated that definitive PBT for patients with unresectable PHC might improve the prognosis. Further large-scale prospective studies are warranted to validate our findings.

Background Factors associated with long-term survival in gemcitabine-concurrent proton radiotherapy (GPT) for non-metastatic, locally advanced pancreatic cancer (LAPC) remain unclear. This study aimed to determine the factors associated with long-term survival in GPT for non-metastatic LAPC. Methods The medical records of 123 patients with LAPC treated with GPT between February 2009 and December 2019 at Hyogo Ion Beam Medical Center were retrospectively reviewed to assess the factors associated with long-term survival outcomes. Results The median overall survival of the total cohort treated with GPT was 18.7 months. The 1- and 2-year overall, local progression-free, and progression-free survival rates were 70.4% and 35.7%, 78.2% and 59.0%, and 38.6% and 20.8%, respectively. Multivariate analysis revealed that LAPCs at the pancreatic body-tail and those without anterior peripancreatic invasion were independently associated with longer overall survival (P = 0.040 and P = 0.015, respectively). The median overall survival of patients with LAPC at the pancreatic body-tail and those with LAPC without anterior peripancreatic invasion were 24.1 and 28.1 months, respectively. LAPCs at the pancreatic body-tail had a higher volume ratio irradiated over 60 Gy equivalents at gross tumor volume than those at the pancreatic head (P P = 0.039). Conclusions GPT is a promising treatment option for patients with LAPC at the pancreatic body-tail and those with LAPC without anterior peripancreatic invasion.

Background Sacral chordomas are rare malignant bone tumors and are often very large for complete resection. Particle therapy for these tumors, which are adjacent to the gastrointestinal tract, is restricted because the tolerance dose of the intestine is low. This study aimed to demonstrate the technical aspects and treatment results of space-making particle therapy with surgical spacer placement for sacral chordoma. We aimed to investigate the dosimetric change in the particle therapy before and after spacer placement and the safety, efficacy, and long-term outcomes of space-making particle therapy. Study Design Twenty-one patients with sacral chordomas who were excluded from typical particle therapy were enrolled between 2007 and 2015. Gore-Tex sheets (WL Gore & Assoc) were folded and placed between the sacral and rectum. Particle therapy with 70.4 Gy (relative biologic effectiveness) was then performed. Results The mean volume that allows 95% of the treatment plan dose of the gross tumor volume and clinical tumor volume after spacer placement was improved to 97.7% and 96.4% from preoperative values of 91.0% and 89.5%, respectively. The recurrence rate within the gross tumor volume was only 4.8%. The 4-year local progression-free survival rate was 68.4%. The 5-year overall survival rate was 100% and the adverse events were acceptable. Conclusions Considering improvements in the dose-volume histogram after spacer placement, low recurrence rates within the gross tumor volume, good survival rates, and low incidences of side effects, treatment of sacral chordoma with space-making particle therapy shows promise.

Our observational study aimed to verify the safety of our original titanium fiducial markers in gynecological cancer by using a simple insertion method. We prospectively evaluated the safety in patients with gynecological cancer who had undergone our insertion procedure of the titanium markers. The decision to implant a titanium marker was at the discretion of each radiation oncologist. The fiducial markers were manufactured by severing ligating clips for surgery into 3–6 mm pieces and were sterilized thereafter. We inserted an 18-gauge injection needle containing the marker before the marker was extruded by a 22-gauge Cattelan needle or shape memory alloy wire into the tumor or tissues close to the tumor. Severe complications within 3 months after implantation were scored according to the National Cancer Institute’s Common Terminology Criteria for Adverse Events version 4.0. Between August 2016 and December 2018, we enrolled 46 patients. Of 46, 44 underwent implantation. The median age was 58.5 years. The most common primary site was the cervix. Two patients experienced detachment of the markers after implantation. No Grade 3 or higher level of complications was observed. Our simple insertion technique for original titanium fiducial markers was well-tolerated.

Purpose This retrospective study aimed to determine the clinical outcomes following particle monotherapy (ie, proton therapy [PT] or carbon ion therapy [CIT]) in patients with sinonasal squamous cell carcinoma at a single institution. Methods and Materials Between August 2001 and March 2012, 59 patients were treated with definitive PT or CIT; none underwent chemotherapy or surgery. Of the patients, 22 (37%) had unresectable disease. PT was used in 38 patients (64%); CIT, 21 patients (36%). Almost half of the patients (n = 29, 47%) received 65.0 Gy (relative biological effectiveness) in 26 fractions. Results The median follow-up period was 30 months (range, 8-127 months) for all patients and 65 months (range, 9-127 months) for the survivors. The 3- and 5-year overall survival rates were 56.2% and 41.6%, respectively; progression-free survival rates, 42.9% and 34.7%, respectively; and local control rates, 54.0% and 50.4%, respectively. Late toxicities of grade ≥3 occurred in 13 patients (22%). Conclusions To our knowledge, this is the largest retrospective study of sinonasal squamous cell carcinoma treated with particle therapy alone. The efficacy of PT and CIT indicated that particle therapy can serve an important role in treating this disease.

Purpose To evaluate the efficacy and safety of definitive proton beam therapy (PBT) for primary sacral chordoma. Methods and Materials We conducted a retrospective analysis of the clinical outcomes of eligible patients with primary sacral chordoma who had undergone definitive PBT with 70.4 Gy (relative biological effectiveness) in 32 fractions at our institution from September 2009 to October 2015. Local progression-free survival, distant metastasis-free survival, disease-free survival, cause-specific survival, and overall survival were evaluated. To explore the factors that influenced local progression, the following parameters were analyzed: sex, the presence of a spacer (Gore-Tex sheets), gross tumor volume, and extent of cranial tumor extension. Adverse events were evaluated using the Common Terminology Criteria for Adverse Events, version 4.0. To assess the impact of PBT on pain relief, the change in pain grades was investigated between the initiation of PBT and the last follow-up visit. Results Thirty-three eligible patients were analyzed. The median follow-up period was 37 months. The 3-year estimated local progression-free survival, distant metastasis-free survival, disease-free survival, cause-specific survival, and overall survival rates were 89.6%, 88.2%, 81.9%, 95.7%, and 92.7%, respectively. No significant association was between the patients’ clinicopathologic characteristics and local progression-free survival. Four patients developed grade 3 adverse events, including acute dermatitis (n = 1), ileus (n = 1), and pain due to sacral insufficiency fractures (n = 2). The pain grades had improved, were unchanged, or had deteriorated in 15, 7, and 11 patients, respectively. Conclusions Definitive PBT with 70.4 Gy (relative biological effectiveness) in 32 fractions is an effective treatment with acceptable toxicity for primary sacral chordoma and has the potential to reduce pain.

Background The primary definitive treatment for abdominopelvic sarcomas (APSs) is resection, although incomplete resection has a negative prognostic impact. Although the effectiveness of particle therapy (PT) as a treatment for APS has already been demonstrated, its application for tumors adjacent to the gastrointestinal tract is frequently restricted, due to extremely low tolerance. Space-making PT, consisting of surgical spacer placement and subsequent PT, has been developed to overcome this limitation. Materials and methods Between June 2006 and June 2018, a total of 75 patients with 12 types of APS underwent space-making PT. Results The 3-year local control rate of all patients was 90.3%. Fourteen surgery-related complications were observed in 12 patients (16%), and complications of Grade 3b or higher were observed in 3 patients. Ninety-five PT-related complications were seen in 66 patients (88.0%), and 13 patients (17.3%) had complications of Grade 3 or higher. The median V95% (volume irradiated with 95% of the treatment planning dose) of the gross tumor volume and clinical target volume were 99.9% and 99.5%, respectively. The median D95% (dose intensity covering 95% of the target volume) of the gross tumor volume/planned dose and clinical target volume/planned dose were 99.4%, and 99.1%, respectively. Conclusion The feasibility and effectiveness of space-making PT have been demonstrated via dosimetric evaluation, and our results indicate that this new strategy may potentially provide an effective and innovative treatment option for advanced APS.

Aim To evaluate the treatment results of radiotherapy (RT) in children and adults with brainstem gliomas (BSGs) and review the previous literature. Methods Thirty patients (14 children, 16 adults) with BSG treated using RT were retrospectively evaluated. The median ages of the children and adults were 8 years (range: 2–16 years) and 49 years (range: 19–75 years), respectively. A histological diagnosis was obtained in 11 patients. The median total radiation dose was 56 Gy (range: 50–70 Gy) with a single fraction size of 1.8–2.0 Gy. Temozolomide was administered concurrently with RT in 14 patients. Results Tumor progression after RT occurred in 26 patients (14 children and 12 adults). Four adults survived without tumor progression. The median survival times for children and adults were 8.5 and 39 months, respectively. The 1-, 2- and 3-year overall survival rates for children/adults were 29%/75%, 14%/68% and 0%/53%, respectively (P = 0.001), and the 1-, 2- and 3-year progression-free survival rates for children/adults were 14%/69%, 0%/49% and 0%/35%, respectively (P < 0.001). Grade 3 or higher acute and late toxicities did not occur. Conclusion In this study, the prognosis of children with BSGs was considerably poorer than that of adults, and our results are consistent with those of previous studies. Efforts should be made to improve the survival outcomes of patients with BSGs, especially children.

The optimal treatment for isolated local recurrence (ILR) of pancreatic adenocarcinoma (PDAC) after surgical resection remains unclear. This study aimed to evaluate the safety and efficacy of proton radiotherapy (PRT) for ILR of PDAC after surgery. The medical records of patients with ILR of PDAC after surgery who underwent proton beam therapy between 2011 and 2015 at Hyogo Ion Beam Medical Center were retrospectively studied. The study analyzed 30 patients (14 women and 16 men) with a median age of 65 years (range 38–81 years) who had initially undergone pancreatoduodenectomy (n = 23) or distal pancreatectomy (n = 7) for their primary tumors. Upon ILR, PRT was administered with a median total cumulative dose of 67.5 gray equivalent (GyE) (range 50–67.5 GyE) using 19 to 25 fractions. For 25 patients, concurrent chemotherapy was administered using gemcitabine (n = 18) or S-1 (n = 7). Four patients (13.3%) experienced acute grade ≥ 3 gastrointestinal toxicities. After a median follow-up period of 17.6 months (range 2.1–50.4 months), 23 patients had experienced tumor progression and 10 had died. Nine patients (30%) experienced local tumor progression. The median overall, progression-free, and local progression-free survival rates were 26.1, 12.3, and 41.2 months, respectively. Pre-PRT serum levels of cancer antigen 19-9 higher than 100 U/mL and duke pancreatic monoclonal antigen type 2 higher than 150 U/mL were significantly associated with shorter progression-free survival rates. Proton radiotherapy for ILR of PDAC after surgery is well tolerated and produces good locoregional control and should be considered for eligible patients.

Objective The management of low-grade glioma (LGG) still remains controversial because the effectiveness of early and extensive resection is unclear, and the use of radiation therapy or chemotherapy is not well-defined. In particular, the importance of prognostic factors for survival remains a matter of discussion. The purpose of this study was to validate prognostic factors for survival in patients with LGG. Materials and methods A consecutive series of 55 patients with WHO grade II LGG treated in our institute between 1983 and 2013 were retrospectively reviewed to determine the prognostic factors for survival. All data were retrospectively analyzed from the aspect of baseline characteristics, pathological findings, genetic change, surgical treatments, adjuvant therapies, and survival time. Cox multivariate analysis was performed to determine the prognostic factors for survival. Results There were 28 patients with diffuse astrocytoma (DA), 21 patients with oligodendroglioma (OG), and 6 patients with oligoastrocytoma (OA) diagnosed on initial surgery. The median overall survival was 193 months and fifteen patients (27.3%) died. A mutation in isocitrate dehydrogenase-1 ( IDH1 ) was found in 72.9% of LGG, and this mutation was positively correlated with methylation of O6-methylguanine-DNA methyltransferase ( MGMT ) ( p = 0.02). A better prognosis was significantly associated with combined IDH1 mutation and MGMT methylation status (both positive vs both negative, HR 0.079 [95% CI 0.008–0.579], p = 0.012 ), as well as histology (OG vs DA and OA, HR 0.158 [95% CI 0.022–0.674], p = 0.011 ) and tumor size ( p = 0.008 ). Conclusions Tumor histology, size and IDH-mutation status are important predictors for prolonged overall survival in patients with LGG and may provide a reliable tool for standardizing future treatment strategies.

Background Some studies have demonstrated that concurrent chemo-radiotherapy is an effective salvage treatment for isolated para-aortic lymph node (PALN) recurrence. However, no studies have compared multi-treatment modalities, such as radiation therapy (RT), concurrent chemoradiotherapy (CCRT), surgery, chemotherapy, and best supportive care (BSC), across a sufficient number of patients with PALN recurrence. We thus aimed to evaluate the clinical outcomes of multi-treatment modalities for isolated PALN recurrence in uterine cervical cancer. Methods Records of 50 patients who were first diagnosed with isolated PALN recurrence after definitive cervical cancer treatment from 2002 to 2016 at our institution were reviewed retrospectively. The initial definitive cervical cancer therapies included RT alone, CCRT, or surgery with or without post-operative RT. The median follow-up time was 33 months. The median age at recurrence diagnosis was 57 years (range, 26–84 years). The median duration between the end of initial treatment and recurrence was 10 months (range, 1–91 months). The median maximum metastatic lesion size was 17 mm (range, 8–60 mm). Twenty-four patients had one or two PALN metastases, while 26 had 3 or more. Eighteen patients were treated for recurrence with RT alone, seven with CCRT, three with surgery, 17 with chemotherapy, and five with BSC. Potential prognostic factors included histopathology, initial FIGO stage, initial treatment, age at recurrence, tumor markers (serum SCC-Ag and CEA) at recurrence, time to recurrence, maximum size of the metastatic lesion, number of metastases, and the recurrence treatment method. Results The 3-year overall survival (OS) rates of all patients were 47.0%. The 3-year OS rate of patients who underwent CCRT for recurrence was 85.7%; surgery, 66.7%; chemotherapy, 48.8%; RT, 41.3%; and BSC, 0% (p = 0.014). Univariate analysis revealed that only the recurrence treatment method was significantly associated with OS. The 3-year local control rate (LCR) and progression free survival (PFS) rate for CCRT were 100 and 71.4%; for surgery, 100 and 66.7%; for chemotherapy, 33.6 and 13.7%; and for RT, 55.5 and 14.1%, respectively (LCR: p = 0.028, PFS: p = 0.059). The number of metastatic lesions, SCC-Ag levels and recurrence treatment method were significantly associated with LCR. Age at recurrence, SCC-Ag levels, and number of metastatic lesions were significantly associated with PFS. Conclusions Although our patient cohort size was small, our results suggest that CCRT may be effective in preventing local disease recurrence in the PALN and may improve OS.

Purpose To retrospectively analyze the treatment outcomes of particle therapy using protons or carbon ions for unresectable or incompletely resected bone and soft tissue sarcomas (BSTSs) of the pelvis. Methods and Materials From May 2005 to December 2014, 91 patients with nonmetastatic histologically proven unresectable or incompletely resected pelvic BSTSs underwent particle therapy with curative intent. The particle therapy used protons (52 patients) or carbon ions (39 patients). All patients received a dose of 70.4 Gy (relative biologic effectiveness) in 32 fractions (55 patients) or 16 fractions (36 patients). Results The median patient age was 67 years (range 18-87). The median planning target volume (PTV) was 455 cm 3 (range 108-1984). The histologic type was chordoma in 53 patients, chondrosarcoma in 14, osteosarcoma in 10, malignant fibrous histiocytoma/undifferentiated pleomorphic sarcoma in 5, and other in 9 patients. Of the 91 patients, 82 had a primary tumor and 9 a recurrent tumor. The median follow-up period was 32 months (range 3-112). The 3-year rate of overall survival (OS), progression-free survival (PFS), and local control was 83%, 72%, and 92%, respectively. A Cox proportional hazards model revealed that chordoma histologic features and a PTV of ≤500 cm 3 were significantly associated with better OS, and a primary tumor and PTV of ≤500 cm 3 were significantly associated with better PFS. Ion type and number of fractions were not significantly associated with OS, PFS, or local control. Late grade ≥3 toxicities were observed in 23 patients. Compared with the 32-fraction protocol, the 16-fraction protocol was associated with significantly more frequent late grade ≥3 toxicities (18 of 36 vs 5 of 55; P Conclusions Particle therapy using protons or carbon ions was effective for unresectable or incompletely resected pelvic BSTS, and the 32-fraction protocol was effective and relatively less toxic. Nevertheless, a longer follow-up period is needed to confirm these results.

Purpose To evaluate the efficacy and safety of carbon-ion radiation therapy (RT) for mucosal melanoma of the head and neck (MMHN) in the Japan Carbon-Ion Radiation Oncology Study Group study. Methods and Materials Patients with MMHN with N0-1M0 status who were treated with carbon-ion RT at 4 institutions in Japan between November 2003 and December 2014 were analyzed retrospectively. Two hundred sixty patients (male, 111; female, 149; median age, 68 years) with histologically proven MMHN were enrolled. Results Primary sites included the nasal cavity in 178 patients, paranasal sinuses in 43, oral cavity in 27, and pharynx in 12. Eighty-six patients had T3 tumors, 147 had T4a tumors, and 27 had T4b tumors. Two hundred fifty-one patients were diagnosed with N0 disease, and 9 with N1 disease. The median total dose and number of fractions were 57.6 Gy RBE (relative biological effectiveness) and 16, respectively. Chemotherapy including dimethyl traizeno imidazole carboxamide was used concurrently in 129 patients. The median follow-up duration was 22 months (range, 1-132 months). The 2-year overall survival and local control rates were 69.4% and 83.9%, respectively. Multivariate analysis showed that gross tumor volume and concurrent chemotherapy were significant prognostic factors for overall survival. Grade 3 and grade 4 late morbidities were observed in 27 and 7 patients (5 developed ipsilateral blindness, 1 mucosal ulcer, and 1 second malignant disease in the irradiated volume), respectively. No patients developed grade 5 late morbidities. Conclusion Carbon-ion RT is a promising treatment option for MMHN.

To evaluate the treatment results of radiotherapy (RT) in children and adults with brainstem gliomas (BSGs) and review the previous literature.Thirty patients (14 children, 16 adults) with BSG treated using RT were retrospectively evaluated. The median ages of the children and adults were 8 years (range: 2-16 years) and 49 years (range: 19-75 years), respectively. A histological diagnosis was obtained in 11 patients. The median total radiation dose was 56 Gy (range: 50-70 Gy) with a single fraction size of 1.8-2.0 Gy. Temozolomide was administered concurrently with RT in 14 patients.Tumor progression after RT occurred in 26 patients (14 children and 12 adults). Four adults survived without tumor progression. The median survival times for children and adults were 8.5 and 39 months, respectively. The 1-, 2- and 3-year overall survival rates for children/adults were 29%/75%, 14%/68% and 0%/53%, respectively (P = 0.001), and the 1-, 2- and 3-year progression-free survival rates for children/adults were 14%/69%, 0%/49% and 0%/35%, respectively (P0.001). Grade 3 or higher acute and late toxicities did not occur.In this study, the prognosis of children with BSGs was considerably poorer than that of adults, and our results are consistent with those of previous studies. Efforts should be made to improve the survival outcomes of patients with BSGs, especially children.

To evaluate the efficacy and safety of a polyglycolic acid (PGA) spacer through physical and animal experiments.The spacer was produced with surgical suture material made of PGA, forming a 3-dimensional nonwoven fabric. For evaluation or physical experiments, 150-MeV proton or 320-MeV carbon-ion beams were used to generate 60-mm width of spread-out Bragg peak. For animal experiments, the abdomens of C57BL/6 mice, with or without the inserted PGA spacers, were irradiated with 20 Gy of carbon-ion beam (290 MeV) using the spread-out Bragg peak. Body weight changes over time were scored, and radiation damage to the intestine was investigated using hematoxylin and eosin stain. Blood samples were also evaluated 24 days after the irradiation. Long-term thickness retention and safety were evaluated using crab-eating macaques.No chemical or structural changes after 100 Gy of proton or carbon-ion irradiation were observed in the PGA spacer. Water equivalency of the PGA spacer was equal to the water thickness under wet condition. During 24 days' observation after 20 Gy of carbon-ion irradiation, the body weights of mice with the PGA spacer were relatively unchanged, whereas significant weight loss was observed in those mice without the PGA spacer (P.05). In mice with the PGA spacer, villus and crypt structure were preserved after irradiation. No inflammatory reactions or liver or renal dysfunctions due to placement of the PGA spacer were observed. In the abdomen of crab-eating macaques, thickness of the PGA spacer was maintained 8 weeks after placement.The absorbable PGA spacer had water-equivalent, bio-compatible, and thickness-retaining properties. Although further evaluation is warranted in a clinical setting, the PGA spacer may be effective to stop proton or carbon-ion beams and to separate normal tissues from the radiation field.

Background A study was undertaken to analyze the efficacy and feasibility of particle beam radiation therapy (PBRT) using carbon ions and protons for the treatment of patients with oligometastatic lung tumors. Methods A total of 47 patients with 59 lesions who underwent PBRT for oligometastatic lung tumors between 2003 and 2011 were included in this study. Patient median age was 66 (range, 39–84) years. The primary tumor site was the colorectum in 11 patients (23.4%), lung in 10 patients (21.3%) and a variety of other sites in 26 patients (55.3%). Thirty-one patients (66%) received chemotherapy prior to PBRT. Thirty-three lesions were treated with 320-MeV carbon ions and 26 were treated with 150- or 210-Mev protons in 1–4 portals. A median total dose of 60 (range, 52.8–70.2) GyE was delivered at the isocenter in 8 (range, 4–26) fractions. Results The median follow-up time was 17 months. The local control, overall survival and progression-free survival rates at 2 years were 79%, 54 and 27% respectively. PBRT-related toxicities were observed; six patients (13%) had grade 2 toxicity (including grade 2 radiation pneumonitis in 2) and six patients (13%) had grade 3 toxicity. Univariate analysis indicated that patients treated with a biologically equivalent dose of 10 (BED10)