Local surgery feasibility and safety after carbon ion radiotherapy for primary bone sarcomas.

BACKGROUND: It is known that several complications are caused by local surgery after radiotherapy. Clinical reports that describe the postoperative complications associated with surgery after carbon ion radiotherapy are sparse. This study aimed to elucidate local surgery feasibility after carbon ion radiotherapy specifically for primary bone sarcomas. METHODS: The medical, surgical, and irradiation records of patients who had local surgery at the area irradiated with carbon ion beams between 2004 and 2018 were reviewed retrospectively to evaluate the feasibility and indication of local surgery after CIRT. RESULTS: There were eight patients who had 10 local surgeries at the irradiated sites among the 42 carbon ion radiotherapy patients. There were seven males and one female with a median age of 50 years (range 26-73 years). The reasons for surgery were three for skin toxicity and associated infection, five for bone collapse, and associated implant failure, and two for tumor regrowth. All surgical fields included the area of more than 60 Gy (RBE) irradiated dose. All three surgical cases caused by skin toxicity and associated infection had Grade I wound complication after surgery according to the Clavien-Dindo Classification. CONCLUSION: Local surgery after CIRT appeared feasible in selected patients with primary bone sarcoma, especially for the patients with bone collapse and associated implant failure. However, infection and prescribed irradiation dose at the incision site must be carefully evaluated.

Poorly Differentiated Chordoma of the Clivus With Loss of SMARCB1 Expression in a Pediatric Patient: A Case Report.

Poorly differentiated chordoma (PDC) is a rare, aggressive subtype of chordoma. A two-year-old girl presented with cervical pain, limb paralysis and respiratory failure. Magnetic resonance imaging and positron emission tomography-computed tomography revealed a tumor compressing the pons at the clivus and osteoblastic metastatic lesions of the left upper arm and right iliac bone. Her tumors shrank substantially after treatment with chemotherapy and proton beam therapy. Our initial diagnosis was an atypical teratoma/rhabdoid tumor, but final diagnosis of PDC was made on the basis of the immunohistochemical expression of brachyury. In addition, the detection of SMARCB1/INI1 mutation confirmed the diagnosis of PDC.

Space-Making Particle Therapy for Unresectable Hilar Cholangiocarcinoma.

INTRODUCTION: Although the primary treatment option for hilar cholangiocarcinoma (HC) has been surgical resection, most patients present with unresectable advanced tumors at the time of diagnosis. Particle therapy (PT) holds great potential for HC, even though the anatomical proximity to the gastrointestinal tract prevents delivering a radical dose to the tumor. Space-making PT (SMPT), consisting of spacer placement surgery and subsequent PT, has been developed to minimize complications and maximize the therapeutic benefit of dose escalation for HC. This study aimed to conduct a dosimetric evaluation and examine the effectiveness of SMPT for the treatment of HC. METHODS: Between 2007 and 2018, 12 patients with unresectable HC treated with SMPT were enrolled. The treatment outcomes and effectiveness of spacer placement surgery were evaluated through analyses of pre- and post-surgical parameters of dose-volume histograms. RESULTS: All patients completed the planned SMPT protocol. The median survival time was 29.6 months, and the 1- and 3-year overall survival rates were 82.5% and 45.8%, respectively. The mean V95% value (volume irradiated with 95% of the planned treatment dose) of the gross tumor volume and clinical target volume after spacer placement surgery improved to 98.5% and 96.6% from preoperative values of 85.6% and 78.1%, respectively (p = 0.0196 and p = 0.0053, respectively). Grade 3 or higher adverse events after SMPT were seen in 6 patients. DISCUSSION/CONCLUSION: SMPT led to improvements in dosimetric parameters and showed good feasibility and excellent outcomes. SMPT can be a promising novel alternative for unresectable HC.

Proton Radiotherapy for Isolated Local Recurrence of Primary Resected Pancreatic Ductal Adenocarcinoma.

BACKGROUND: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: Proton radiotherapy for ILR of PDAC after surgery is well tolerated and produces good locoregional control and should be considered for eligible patients.

A retrospective multicenter study of carbon-ion radiotherapy for major salivary gland carcinomas: Subanalysis of J-CROS 1402 HN.

A retrospective multicenter study was carried out to assess the clinical outcomes of carbon-ion radiotherapy for head and neck malignancies (Japan Carbon-Ion Radiation Oncology Study Group [J-CROS] study: 1402 HN). We evaluated the safety and efficacy of carbon-ion radiotherapy in patients with major salivary gland carcinoma. Sixty-nine patients treated with carbon-ion radiotherapy at four Japanese institutions were analyzed. Thirty-three patients (48%) had adenoid cystic carcinomas, 10 (14%) had mucoepidermoid carcinomas, and 26 (38%) had other disease types. Three patients (4%) had T1 disease, 8 (12%) had T2, 25 (36%) had T3, and 33 (48%) had T4. The median radiation dose was 64 Gy (relative biological effectiveness) in 16 fractions. The median gross tumor volume was 27 mL. The median follow-up period was 32.7 months. The 3-year local control rate and overall survival rate were 81% and 94%, respectively. Regarding acute toxicities, seven patients had grade 3 mucositis and seven had grade 3 dermatitis. Regarding late toxicities, one patient had grade 3 dysphagia and one had a grade 3 brain abscess. No grade 4 or worse late reactions were observed. In conclusion, definitive carbon-ion radiotherapy was effective with acceptable toxicity for major salivary gland carcinomas.

Multi-institutional retrospective study of mucoepidermoid carcinoma treated with carbon-ion radiotherapy.

This study aimed to evaluate the clinical outcomes of patients with mucoepidermoid carcinomas in the head and neck treated with carbon-ion radiotherapy. Data from 26 patients who underwent carbon-ion radiotherapy in four facilities were analyzed in this multi-institutional retrospective study: the Japan Carbon-ion Radiation Oncology Study Group. The median follow-up time was 34 months. One patient experienced local recurrence, and the 3-year local control rate was 95%. One patient developed lymph node recurrence and five developed distant metastases. The 3-year progression-free survival rate was 73%. Five patients died, two of mucoepidermoid carcinoma and three of intercurrent disease. The 3-year overall survival rate was 89%. Acute mucositis and dermatitis of grade 3 or higher were experienced by 19% and 8% of patients, respectively; these improved with conservative therapy. Late mucositis and osteonecrosis of jaw were observed in 12% and 23% of patients, respectively. The 3-year cumulative rate of any late adverse event of grade 3 or higher was 14%. None of the patients died of the acute or late adverse events. Carbon-ion radiotherapy was efficacious and safe for treating mucoepidermoid carcinoma in this multi-institutional retrospective study (registration no. UMIN000024473). We are currently undertaking a prospective multicenter study.

Long-term follow-up after proton beam therapy for pediatric tumors: a Japanese national survey.

Proton beam therapy (PBT) is a potential new alternative to treatment with photon radiotherapy that may reduce the risk of late toxicity and secondary cancer, especially for pediatric tumors. The goal of this study was to evaluate the long-term benefits of PBT in cancer survivors. A retrospective observational study of pediatric patients who received PBT was performed at four institutions in Japan. Of 343 patients, 62 were followed up for 5 or more years. These patients included 40 males and 22 females, and had a median age of 10 years (range: 0-19 years) at the time of treatment. The irradiation dose ranged from 10.8 to 81.2 GyE (median: 50.4 GyE). The median follow-up period was 8.1 years (5.0-31.2 years). The 5-, 10- and 20-year rates for grade 2 or higher late toxicities were 18%, 35% and 45%, respectively, and those for grade 3 or higher late toxicities were 6%, 17% and 17% respectively. Univariate analysis showed that the irradiated site (head and neck, brain) was significantly associated with late toxicities. No malignant secondary tumors occurred within the irradiated field. The 10- and 20-year cumulative rates for all secondary tumors, malignant secondary tumors, and malignant nonhematologic secondary tumors were 8% and 16%, 5% and 13%, and 3% and 11%, respectively. Our data indicate that PBT has the potential to reduce the risk of late mortality and secondary malignancy. Longer follow-up is needed to confirm the benefits of PBT for pediatric tumors.

Proton beam therapy for bone sarcomas of the skull base and spine: A retrospective nationwide multicenter study in Japan.

We conducted a retrospective, nationwide multicenter study to evaluate the clinical outcomes of proton beam therapy for bone sarcomas of the skull base and spine in Japan. Eligibility criteria included: (i) histologically proven bone sarcomas of the skull base or spine; (ii) no metastases; (iii) ≥20 years of age; and (iv) no prior treatment with radiotherapy. Of the 103 patients treated between January 2004 and January 2012, we retrospectively analyzed data from 96 patients who were followed-up for >6 months or had died within 6 months. Seventy-two patients (75.0%) had chordoma, 20 patients (20.8%) had chondrosarcoma, and four patients (7.2%) had osteosarcoma. The most frequent tumor locations included the skull base in 68 patients (70.8%) and the sacral spine in 13 patients (13.5%). Patients received a median total dose of 70.0 Gy (relative biological effectiveness). The median follow-up was 52.6 (range, 6.3-131.9) months. The 5-year overall survival, progression-free survival, and local control rates were 75.3%, 49.6%, and 71.1%, respectively. Performance status was a significant factor for overall survival and progression-free survival, whilst sex was a significant factor for local control. Acute Grade 3 and late toxicities of ≥Grade 3 were observed in nine patients (9.4%) each (late Grade 4 toxicities [n = 3 patients; 3.1%]). No treatment-related deaths occurred. Proton beam therapy is safe and effective for the treatment of bone sarcomas of the skull base and spine in Japan. However, larger prospective studies with a longer follow-up are warranted.

Reirradiation for recurrent head and neck cancers using charged particle or photon radiotherapy.

OBJECTIVE: To examine the outcomes of reirradiation for recurrent head and neck cancers using different modalities. METHODS: This retrospective study included 26 patients who received charged particle radiotherapy (CP) and 150 who received photon radiotherapy (117 CyberKnife radiotherapy [CK] and 36 intensity-modulated radiotherapy [IMRT]). Inverse probability of treatment weighting (IPTW) involving propensity scores was used to reduce background selection bias. RESULTS: Higher prescribed doses were used in CP than photon radiotherapy. The 1­year overall survival (OS) rates were 67.9% for CP and 54.1% for photon radiotherapy (p = 0.15; 55% for CK and 51% for IMRT). In multivariate Cox regression, the significant prognostic factors for better survival were nasopharyngeal cancer, higher prescribed dose, and lower tumor volume. IPTW showed a statistically significant difference between CP and photon radiotherapy (p = 0.04). The local control rates for patients treated with CP and photon radiotherapy at 1 year were 66.9% (range 46.3-87.5%) and 67.1% (range 58.3-75.9%), respectively. A total of 48 patients (27%) experienced toxicity grade ≥3 (24% in the photon radiotherapy group and 46% in the CP group), including 17 patients with grade 5 toxicity. Multivariate analysis revealed that younger age and a larger planning target volume (PTV) were significant risk factors for grade 3 or worse toxicity. CONCLUSION: CP provided superior survival outcome compared to photon radiotherapy. Tumor volume, primary site (nasopharyngeal), and prescribed dose were identified as survival factors. Younger patients with a larger PTV experienced toxicity grade ≥3.

Hypofractionated stereotactic radiotherapy for brain metastases from lung cancer : Evaluation of indications and predictors of local control.

AIM: To evaluate the efficacy and toxicity of hypofractionated stereotactic radiotherapy (HSRT) for brain metastases (BMs) from lung cancer, and to explore prognostic factors associated with local control (LC) and indication. PATIENTS AND METHODS: We evaluated patients who were treated with linac-based HSRT for BMs from lung cancer. Lesions treated with stereotactic radiosurgery (SRS) in the same patients during the same periods were analysed and compared with HSRT in terms of LC or toxicity. There were 53 patients with 214 lesions selected for this analysis (HSRT: 76 lesions, SRS: 138 lesions). For HSRT, the median prescribed dose was 35 Gy in 5 fractions. RESULTS: The 1­year LC rate was 83.6 % in HSRT; on multivariate analysis, a planning target volume (PTV) of <4 cm(3), biologically effective dose (BED10) of ≥51 Gy, and adenocarcinoma were significantly associated with better LC. Moreover, in PTVs ≥ 4 cm(3), there was a significant difference in LC between BED10 < 51 Gy and ≥ 51 Gy (p = 0.024). On the other hand, in PTVs < 4 cm(3), both HSRT and SRS had good LC with no significant difference (p = 0.195). Radiation necrosis emerged in 5 of 76 lesions (6.6 %) treated with HSRT and 21 of 138 (15.2 %) lesions treated with SRS (p = 0.064). CONCLUSION: Linac-based HSRT was safe and effective for BMs from lung cancer, and hence might be particularly useful in or near an eloquent area. PTV, BED10, and pathological type were significant prognostic factors. Furthermore, in BMs ≥ 4 cm(3), a dose of BED ≥ 51 Gy should be considered.

Comparison of clinical and functional outcome between surgical treatment and carbon ion radiotherapy for pelvic chondrosarcoma.

BACKGROUND: As there are no reports of studies in patients with pelvic chondrosarcoma treated with carbon ion radiotherapy (CIRT), the aim of this study was to evaluate the applicability of CIRT for patients with chondrosarcoma of the pelvis. METHODS: The medical records of 31 patients with chondrosarcoma of the pelvis treated either by surgical resection or by CIRT between 1983 and 2014 were reviewed. There were 22 males and 9 females with a median age of 43 years (range 16-77 years). The median duration of follow-up was 66 months (range 5-289 months). Twenty-four patients underwent surgery, and 7 patients received CIRT (70.4 GyE in 16 fractions over 4 weeks). RESULTS: The overall local recurrence rate was 32 %, and the estimated overall 5- and 10-year survival rates were 72 and 57 %, respectively. The mean Musculoskeletal Tumor Society functional score was 59 %. The treatment procedures (surgery or CIRT) did not affect overall survival (P = 0.347). However, the patients who underwent surgery had impaired function compared with those who received CIRT (P = 0.03). CONCLUSION: Although more patients need to be monitored to assess the clinical and functional outcomes of CIRT for patients with chondrosarcoma of the pelvis, this treatment might offer an acceptable alternative.

Carbon ion radiotherapy for desmoid tumor of the abdominal wall: a case report.

BACKGROUND: Desmoid tumors, which are associated with familial adenomatous polyposis (FAP), tend to occur frequently in the abdominal wall and mesentery. Currently, there are no recognized treatments other than surgery, and frequent surgeries result in gastrointestinal obstructions and functional gastrointestinal disorders. CASE PRESENTATION: After surgery that was performed on a 39-year-old patient with FAP, we performed a second tumor excision which was the procedure used for frequently occurring mesenteric desmoid tumors. It was determined that the enlarged tumor would be difficult to operate on through an abdominal incision. Subsequently, the carbon ion radiotherapy of 50 Gy was then performed on the patient. Three years later, the tumor still remains reduced in size. In addition, we have not observed any negative effect on the digestive tract. CONCLUSIONS: This is the first instance that the carbon ion radiotherapy has been effective for the unresected desmoid tumor, and it is believed that this will become the one effective option for the treatment of desmoid tumors.

[An 85-Year-Old Man with Lymph Node Metastasis of Recurrent Rectal Cancer Treated UsingProton Beam Therapy].

There are few reports that describe the efficacy of proton beam therapy for lymph node metastasis of recurrent rectal cancer, and carbon ion radiotherapy yields higher local tumor control rates. Proton beam therapy needs a longer treatment period but is less toxic to adjacent healthy organs compared to carbon ion radiotherapy. Here we report an 85-year-old man who underwent curative surgery for rectal and sigmoid cancer at the age of 76 years. After 4 years and 2 months, he had liver metastases at S3 and S8, both of which were resected. Eight years and 6 months after primary resection, CT imaging revealed a solitary lymph node metastasis of 28mm in the minor axis, adjacent to the portal vein and IVC. Because of the location and patient's age, proton beam therapy was selected as the treatment strategy, rather than surgery or chemotherapy. A total of 67.5 GyE/25 fx proton beam therapy was applied. CT imaging 4months after irradiation revealed a partial response(PR)and the tumor had shrunk to 8mm. PR continued for 2 years and 1 month. Although the tumor relapsed after 3 years of irradiation and had grown to 16 mm, the patient had no adverse events or symptoms throughout this period. Proton beam therapy may be one of the options for tumors at difficult locations in fragile patients because of its reduced toxicity.

Particle therapy for clinically diagnosed stage I lung cancer: comparison with pathologically proven non-small cell lung cancer.

BACKGROUND: The purpose of the present study was to present the treatment outcomes of particle therapy for indeterminate pulmonary nodules (IPNs) diagnosed as stage I non-small cell lung cancer, including a comparative analysis involving pathologically proven lung cancer (PPLC). MATERIAL AND METHODS: A total of 54 patients (57 lesions) who underwent particle therapy for IPNs were enrolled in this study. Median patient age was 76 (range 52-87) years. T-classification was: T1a, 30; T1b, 16; and T2a, 11. Particle therapy using protons or carbon ions was delivered at total doses of 52.8-80 Gy equivalent in 4-26 fractions. The PPLC cohort included 111 patients. RESULTS: The median follow-up time was 41 (range 7-90) months. For all IPN patients, the three-year overall survival, progression-free survival, local control and distant progression-free survival rates were 90%, 72%, 94% and 79%, respectively. Grade 2 toxicities were radiation pneumonitis (19%), dermatitis (9%), rib fracture (2%), chest wall pain (2%) and neuropathy (2%). No ≥grade 3 toxicities were observed. In univariate analysis, the IPN group showed significantly better survival relative to the PPLC group. However, after adjustment for baseline imbalances between these two groups in multivariate analysis, pathological confirmation did not correlate with survival. CONCLUSIONS: Particle therapy for IPNs provided favorable outcomes with minimal toxicities, which may be comparable to those for PPLC patients. Further studies are needed to clarify the optimal management of IPN patients.

Unexpected radiation laryngeal necrosis after carbon ion therapy using conventional dose fractionation for laryngeal cancer.

Carbon ion therapy is a type of radiotherapy that can deliver high-dose radiation to a tumor while minimizing the dose delivered to organs at risk. Moreover, carbon ions are classified as high linear energy transfer radiation and are expected to be effective for even photon-resistant tumors. A 73-year-old man with glottic squamous cell carcinoma, T3N0M0, refused laryngectomy and received carbon ion therapy of 70 Gy (relative biological effectiveness) in 35 fractions. Three months after the therapy, the patient had an upper airway inflammation, and then laryngeal edema and pain occurred. Five months after the therapy, the airway stenosis was severe and computed tomography showed lack of the left arytenoid cartilage and exacerbation of laryngeal necrosis. Despite the treatment, 5 and a half months after the therapy, the laryngeal edema and necrosis had become even worse and the surrounding mucosa was edematous and pale. Six months after the therapy, pharyngolaryngoesophagectomy and reconstruction with free jejunal autograft were performed. The surgical specimen pathologically showed massive necrosis and no residual tumor. Three years after the carbon ion therapy, he is alive without recurrence. The first reported laryngeal squamous cell carcinoma case treated with carbon ion therapy resulted in an unexpected radiation laryngeal necrosis. Tissue damage caused by carbon ion therapy may be difficult to repair even for radioresistant cartilage; therefore, hollow organs reinforced by cartilage, such as the larynx, may be vulnerable to carbon ion therapy. Caution should be exercised when treating tumors in or adjacent to such organs with carbon ion therapy.

Selective killing of oncogenically transformed cells through a ROS-mediated mechanism by beta-phenylethyl isothiocyanate.

Reactive oxygen species (ROS) stimulate cell proliferation and induce genetic instability, and their increase in cancer cells is often viewed as an adverse event. Here, we show that such abnormal increases in ROS can be exploited to selectively kill cancer cells using beta-phenylethyl isothiocyanate (PEITC). Oncogenic transformation of ovarian epithelial cells with H-Ras(V12) or expression of Bcr-Abl in hematopoietic cells causes elevated ROS generation and renders the malignant cells highly sensitive to PEITC, which effectively disables the glutathione antioxidant system and causes severe ROS accumulation preferentially in the transformed cells due to their active ROS output. Excessive ROS causes oxidative mitochondrial damage, inactivation of redox-sensitive molecules, and massive cell death. In vivo, PEITC exhibits therapeutic activity and prolongs animal survival.

Particle radiotherapy using protons or carbon ions for unresectable locally advanced head and neck cancers with skull base invasion.

OBJECTIVE: To study the oncological outcome of the patients with unresectable locally advanced primary head and neck cancers invading the skull base, treated with particle radiotherapy. METHODS: Fifty-seven patients with unresectable primary head and neck cancers invading the skull base received proton or carbon ion radiotherapy as definitive treatment at Hyogo Ion Beam Medical Center between 2003 and 2009. Forty-seven patients were treated with proton radiotherapy and 10 patients were treated with carbon ion radiotherapy. A retrospective review was performed with clinical charts and recorded imagings. RESULTS: With a median follow-up of 32 months, the 3-year actual survival and local progression-free rates of all the patients were 61 and 56%, respectively. The 3-year actual survival rates of adenoid cystic carcinoma, squamous cell carcinoma, olfactory neuroblastoma, adenocarcinoma and malignant melanoma were 83, 44, 75, 0 and 38%, respectively. The 3-year actual local control rates of adenoid cystic carcinoma, squamous cell carcinoma, olfactory neuroblastoma, adenocarcinoma and malignant melanoma were 63, 31, 83, 50 and 0%, respectively. Distant metastasis was observed in 13 of 25 patients in adenoid cystic carcinoma, two of 14 patients in squamous cell carcinoma, one of six patients with olfactory neuroblastoma, two of four patients with adenocarcinoma, three of four patients with malignant melanoma and two of three patients with undifferentiated carcinoma. Mucositis and dermatitis were seen as acute toxicities. The most common late toxicity was visual disorder. Grades 2, 3 and 4 visual disorders were observed in seven, five and two patients, respectively. CONCLUSIONS: Proton and carbon ion radiotherapy resulted in satisfactory local control in patients with locally advanced unresectable primary head and neck cancers invading the skull base.

Comparison of passive-scattered and intensity-modulated proton beam therapy of craniospinal irradiation with proton beams for pediatric and young adult patients with brain tumors.

PURPOSE: To investigate the dose stability of craniospinal irradiation based on irradiation method of proton beam therapy (PBT). METHODS AND MATERIALS: Twenty-four pediatric and young adult brain tumor patients (age: 1-24 years) were examined. Treatment method was passive-scattered PBT (PSPT) in 8 patients and intensity-modulated PBT (IMPT) in 16 patients. The whole vertebral body (WVB) technique was used in 13 patients whose ages were younger than 10, and vertebral body sparing (VBS) technique was used for the remaining 11 patients aged 10 and above. Dose stability of planning target volume (PTV) against set-up error was investigated. RESULTS: The minimum dose (Dmin) of IMPT was higher than that of PSPT (p = 0.01). Inhomogeneity index (INH) of IMPT was lower than that of PSPT (p = 0.004). When the irradiation field of the cervical spinal cord level (C level) was shifted, the maximum dose (Dmax) was lower in IMPT, and mean dose (Dmean) was higher than PSPT as movement became greater to the cranial-caudal direction (p = 0.000-0.043). Dmin was higher and INH was lower in IMPT in all directions (p = 0.000-0.034). When the irradiation field of the lumber spinal cord level (L level) was shifted, Dmax was lower in IMPT as movement became greater to the cranial direction (p = 0.000-0.028). Dmin was higher and INH was lower in IMPT in all directions (p = 0.000-0.022). CONCLUSIONS: The PTV doses of IMPT and PSPT are robust and stable in both anterior-posterior and lateral directions at both C level and L level, but IMPT is more robust and stable than PSPT for cranial-caudal movements. TRIAL REGISTRY: Clinical Trial Registration number: No. 04-03.

Innovative Combination Treatment to Expand the Indications of Particle Therapy: Spacer Placement Surgery Using Bio-Absorbable Polyglycolic Acid Spacer.

BACKGROUND: Particle therapy has favorable dose distribution and high curability. However, radiotherapy for malignant tumors adjacent to the gastrointestinal tract is contraindicated owing to its low tolerance. To overcome this, combination treatment with surgery to make a space between the tumor and adjacent gastrointestinal tract followed by particle therapy has been developed. Several materials have been used for the spacer and recently, we developed the absorbable polyglycolic acid (PGA) spacer, which has been used since 2019. This study is the first report of consecutive case series of spacer placement surgery using the PGA spacer. STUDY DESIGN: Fifty consecutive patients undergoing spacer placement surgery with the PGA spacer were evaluated. Postoperative laboratory data, morbidity related to the treatment, and spacer volume after treatment were evaluated. RESULTS: There were no treatment-related deaths, and all but 2 patients completed combination treatment. The median ratios of postoperative PGA spacer volume to the pretreatment volume were 96.9%, 87.7%, and 74.6% at weeks 2, 4, and 8, respectively. The spacer volume was maintained at 80% at 7 weeks and was predicted to be 50% at 15 weeks and 20% in 24 weeks. CONCLUSIONS: Spacer placement surgery using the PGA spacer was feasible and tolerable. The PGA spacers maintained sufficient thickness during the duration of subsequent particle therapy. Combination treatment using the PGA spacer is innovative and has the potential to become a new standard curative local treatment.