RESUMO
BACKGROUND: Clear cell odontogenic carcinoma (CCOC) is a rare odontogenic malignant tumor. The standard treatment for CCOC is surgical resection and adjuvant radiotherapy (RT). Radiotherapy is generally considered in inoperable cases. However, there are no reports on definitive RT for CCOC, and the role of RT in patients with inoperable CCOC remains unknown. Therefore, in this report, we present two cases of carbon-ion (C-ion) RT for CCOC. CASE PRESENTATION: In case 1, a 73-year-old man with mandibular CCOC presented with recurrence in the inferior temporal fossa after two tumor resections. The tumor was considered inoperable, and C-ion RT (57.6 Gy in 16 fractions) was administered. The tumor remained controlled even after 20 months of C-ion RT; however, the patient died of other causes. In case 2, a 34-year-old man with maxillary CCOC presented with recurrence in the left sinonasal region after two tumor resections. The tumor was considered inoperable, and C-ion RT (64 Gy in 16 fractions) was administered. However, recurrence was observed in the irradiated field 19 months after the treatment. Subsequently, C-ion RT (64 Gy in 16 fractions) was repeated for the recurrent tumors. Seven years and 6 months after the initial irradiation, the tumor remains controlled, and the patient is alive without any unexpected serious adverse events. CONCLUSION: C-ion RT may be an effective treatment option for patients with inoperable CCOC.
Assuntos
Radioterapia com Íons Pesados , Recidiva Local de Neoplasia , Tumores Odontogênicos , Humanos , Masculino , Idoso , Tumores Odontogênicos/radioterapia , Tumores Odontogênicos/patologia , Tumores Odontogênicos/cirurgia , Radioterapia com Íons Pesados/métodos , Recidiva Local de Neoplasia/radioterapia , Recidiva Local de Neoplasia/patologia , Adulto , Adenocarcinoma de Células Claras/radioterapia , Adenocarcinoma de Células Claras/patologia , Adenocarcinoma de Células Claras/cirurgia , Prognóstico , Neoplasias Mandibulares/radioterapia , Neoplasias Mandibulares/patologia , Neoplasias Mandibulares/cirurgia , Evolução FatalRESUMO
PURPOSE: Radiation-induced lymphopenia (RIL) is associated with poor prognosis in patients with locally advanced pancreatic cancers. However, there are no reports comparing the effects of carbon ion radiation therapy (CIRT) and photon beam radiation therapy (RT) on the development of RIL. Differences in RIL after CIRT or photon beam RT and predictive factors for RIL in patients with locally advanced pancreatic cancer were investigated. MATERIALS AND METHODS: This retrospective study cohort included 834 patients who received concurrent chemoradiotherapy (CCRT) in 2 separate institutions: 337 and 497 in the CIRT and photon beam RT groups, respectively. Severe RIL was defined as an absolute lymphocyte count (ALC) <0.5 × 109 cells/L. A 1:1 propensity score-matching analysis was performed between the CIRT and photon beam RT groups. Patients were categorized into 3 groups according to the development of recovery from severe RIL: no severe RIL (Group A), recovery from severe RIL (Group B), and no recovery from severe RIL (Group C). Logistic regression analysis was performed to identify the predictive value of severe RIL. The prognostic factors of overall survival (OS) were determined using Cox regression analysis. RESULTS: After propensity score matching, the baseline ALC and planning target volume of the CIRT and photon beam RT groups were comparable. During CCRT, the ALC of the entire cohort decreased and was significantly lower in the photon beam RT group than in the CIRT group (P < .001). Multivariate logistic regression analysis showed that CIRT reduced severe RIL more than photon beam RT. After adjusting for other factors, the RT modality and RIL were significantly associated with OS. Photon beam RT showed a significantly worse OS than CIRT, and Group C showed a significantly worse OS than Group A. CONCLUSIONS: CIRT seems to reduce the development of severe RIL. The RT modality and development/recovery from severe RIL were associated with OS in patients who received CCRT for locally advanced pancreatic cancer. The reduction of severe RIL through optimized RT may be essential for improving treatment outcomes.
RESUMO
This feasibility study confirmed the initial safety and efficacy of a novel carbon-ion radiotherapy (CIRT) using linear energy transfer (LET) painting for head and neck cancer. This study is the first step toward establishing CIRT with LET painting in clinical practice and making it a standard practice in the future.
Assuntos
Estudos de Viabilidade , Neoplasias de Cabeça e Pescoço , Radioterapia com Íons Pesados , Transferência Linear de Energia , Dosagem Radioterapêutica , Humanos , Neoplasias de Cabeça e Pescoço/radioterapia , Radioterapia com Íons Pesados/métodos , Masculino , Feminino , Idoso , Pessoa de Meia-IdadeRESUMO
PURPOSE: It is difficult to effectively cure patients with unresectable locally recurrent colorectal cancers (LRCRCs) using conventional chemotherapy or chemoradiation therapy. Furthermore, treatment options vary depending on the patient's history of radiation therapy. Carbon-ion radiation therapy (CIRT) is a potentially curative treatment for these patients. Here, we compare the treatment outcomes of radiation therapy-naïve cases (nRT) and re-irradiation cases (reRT). METHODS AND MATERIALS: Patients with LRCRC treated with CIRT at QST Hospital between 2003 and 2019 were eligible. CIRT was administered daily 4 d/wk for 16 fractions. The total irradiated dose was set at 73.6 Gy (relative biologic effectiveness-weighted dose [RBE]) for nRT and 70.4 Gy (RBE) for reRT patients. RESULTS: We included 390 nRT cases and 83 reRT cases. The median follow-up period from the initiation of CIRT was 48 (5-208) months. The 3-year overall survival (OS) rates for nRT and reRT were 73% (95% CI, 68%-77%) and 76% (65%-84%), respectively. The 5-year OS rates were 50% (45%-55%) and 50% (38%-61%), respectively. These rates did not differ significantly (P = .55). The 3-year local control (LC) rates for nRT (73.6 Gy) and reRT (70.4 Gy) cases were 80% (75%-84%) and 80% (68%-88%), respectively. The 5-year LC rates were 72% (67%-78%) and 69% (55%-81%), respectively, without a significant difference (P = .56). CONCLUSIONS: Our results suggest that CIRT for LRCRC is a very effective and promising treatment for both nRT and reRT cases.
Assuntos
Neoplasias Colorretais , Radioterapia com Íons Pesados , Reirradiação , Humanos , Reirradiação/métodos , Radioterapia com Íons Pesados/efeitos adversos , Resultado do Tratamento , Neoplasias Colorretais/radioterapia , Carbono , Recidiva Local de NeoplasiaRESUMO
Purpose: This study aimed to clarify the predictive factors for otitis media with effusion (OME) due to Eustachian tube dysfunction in patients treated with carbon-ion radiation therapy (CIRT) for head and neck cancers. Methods and Materials: We investigated patients with head and neck cancer whose Eustachian tube was irradiated by CIRT between October 2013 and December 2018 at our institution. OME severity was assessed by the proportion of mastoid cell opacification of magnetic resonance or computed tomography imaging (grade 0: <5% of volume of mastoid cell with opacification by fluid collection; grade 1: 6%-33%; grade 2: 34%-67%; and grade 3: 68%-100%). Clinical factors and dosimetric parameters affecting the development of grade 2 to 3 OME were analyzed using a log-rank test and Cox proportional hazards model. Results: In total, 141 patients were analyzed. The median follow-up period was 25.2 months. Grade 2 to 3 OME was observed in 65 patients, with a median incidence period of 6.5 months. According to the multivariate analysis, the mean dose of the cartilage part was a significant independent predictive parameter of grade 2 to 3 OME. The 2-year incidence rate of patients with a mean dose of the cartilage part of <40.59 Gy (relative biological effectiveness) and ≥40.59 Gy (relative biological effectiveness) was 24.2% (95% confidence interval, 15.1%-37.4%) and 66.4% (95% confidence interval, 54.5%-78.0%), respectively. Conclusions: Our findings may be useful to predict the risk of grade 2 to 3 OME due to Eustachian tube dysfunction before CIRT.
RESUMO
We compared the dose distributions of carbon-ion pencil beam scanning (C-PBS), proton pencil beam scanning (P-PBS) and Volumetric Modulated Arc Therapy (VMAT) for locally recurrent rectal cancer. The C-PBS treatment planning computed tomography (CT) data sets of 10 locally recurrent rectal cancer cases were randomly selected. Three treatment plans were created using identical prescribed doses. The beam angles for C-PBS and P-PBS were identical. Dosimetry, including the dose received by 95% of the planning target volume (PTV) (D95%), dose to the 2 cc receiving the maximum dose (D2cc), organ at risk (OAR) volume receiving > 15Gy (V15) and > 30Gy (V30), was evaluated. Statistical significance was assessed using the Wilcoxon signed-rank test. Mean PTV-D95% values were > 95% of the volume for P-PBS and C-PBS, whereas that for VMAT was 94.3%. However, PTV-D95% values in P-PBS and VMAT were < 95% in five and two cases, respectively, due to the OAR dose reduction. V30 and V15 to the rectum/intestine for C-PBS (V30 = 4.2 ± 3.2 cc, V15 = 13.8 ± 10.6 cc) and P-PBS (V30 = 7.3 ± 5.6 cc, V15 = 21.3 ± 13.5 cc) were significantly lower than those for VMAT (V30 = 17.1 ± 10.6 cc, V15 = 55.2 ± 28.6 cc). Bladder-V30 values with P-PBS/C-PBS (3.9 ± 4.8 Gy(RBE)/3.0 ± 4.0 Gy(RBE)) were significantly lower than those with VMAT (7.9 ± 8.1 Gy). C-PBS provided superior dose conformation and lower OAR doses compared with P-PBS and VMAT. C-PBS may be the best choice for cases in which VMAT and P-PBS cannot satisfy dose constraints. C-PBS could be another choice for cases in which VMAT and P-PBS cannot satisfy dose constraints, thereby avoiding surgical resection.
Assuntos
Radioterapia de Intensidade Modulada , Neoplasias Retais , Humanos , Prótons , Reto , Radioterapia de Intensidade Modulada/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Dosagem Radioterapêutica , Recidiva Local de Neoplasia/radioterapia , Neoplasias Retais/radioterapia , Doença CrônicaAssuntos
Neoplasias dos Ductos Biliares , Colangiocarcinoma , Seguro , Neoplasias Pancreáticas , Humanos , Colangiocarcinoma/terapia , Neoplasias dos Ductos Biliares/patologia , Neoplasias Pancreáticas/radioterapia , Neoplasias Pancreáticas/patologia , Ductos Biliares Intra-Hepáticos/patologia , Neoplasias PancreáticasRESUMO
This study aimed to evaluate the uptake of the clinical effectiveness of [S-methyl-11C]-L-methionine positron emission tomography/computed tomography (MET PET/CT) in patients with esophageal cancer and to investigate MET PET/CT imaging parameters to assess early response for esophageal cancer with neoadjuvant carbon ion radiotherapy (CIRT). MET PET/CT scans were performed in nineteen patients before and 3 weeks after completion of CIRT. After Surgery, the effect of neoadjuvant CIRT was investigated by examining the relationship between each parameter of MET uptake and the histological assessment (grade and tumor residual ratio). Four parameters of MET uptake were the maximum and minimum standardized uptake values of pre and post CIRT (pre-SUVmax, pre-SUVmean, post-SUVmax, and post-SUVmean). MET PET/CT imaging of esophageal cancer was clearly demonstrated. The post-SUVmax was the most suitable parameter. When the cutoff value was set as post-SUVmax = 6.21, the sensitivity, the specificity, and the accuracy of Grades 3 were 100.0%, 63.6%, and 78.9%, respectively. And there was a positive relationship between the tumor residual ratio and post-SUVmax (R2 = 0.38, p < 0.005). MET PET/CT is clinically useful for the assessment of early response to neoadjuvant CIRT in esophageal cancer. Particularly, post-SUVmax is considered a promising PET imaging parameter.
Assuntos
Neoplasias Esofágicas , Radioterapia com Íons Pesados , Neoplasias Esofágicas/diagnóstico por imagem , Neoplasias Esofágicas/radioterapia , Fluordesoxiglucose F18 , Radioterapia com Íons Pesados/métodos , Humanos , Metionina , Terapia Neoadjuvante , Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada/métodos , Tomografia por Emissão de Pósitrons , Compostos RadiofarmacêuticosRESUMO
BACKGROUND: Chordoma is a rare, locally invasive neoplasm of the axial skeleton. Complete resection is often difficult, especially for the upper-cervical (C1-2) spine. We evaluated the efficacy and safety of carbon-ion radiotherapy (CIRT) for unresectable C1-2 chordoma. METHODS: Patients with C1-2 chordoma treated with definitive CIRT (60.8 Gy [RBE] in 16 fractions) were retrospectively analyzed. We evaluated OS, LC, PFS, and toxicity. RESULTS: Nineteen eligible patients all completed the planned course of CIRT. With the median follow-up 68 months (range: 29-144), median OS was 126 months (range: 36-NA). Five-year OS, LC, and PFS were 68.4% (95% CI, 42.8%-84.4%), 75.2% (46.1%-90.0%), and 64.1% (36.3%-82.3%), respectively. Regarding acute toxicity of grade ≥3, there was only one grade 3 mucositis. Late toxicity included radiation-induced myelitis (grade 3 in 1 patient; 5.3%), and compression fractures (n = 5; 26.3%). CONCLUSIONS: High-dose CIRT is a promising treatment option for unresectable upper cervical chordoma.
Assuntos
Cordoma , Radioterapia com Íons Pesados , Lesões por Radiação , Carbono/uso terapêutico , Cordoma/radioterapia , Radioterapia com Íons Pesados/efeitos adversos , Humanos , Lesões por Radiação/tratamento farmacológico , Estudos RetrospectivosRESUMO
BACKGROUND: Pancreatic cancer is a disease of the elderly; patients >65 years are 60% of the cases. Due to multiple comorbidities, treating these patients is challenging. We report the efficacy and safety of carbon ion radiotherapy (C-ion RT) in octogenarians. METHODS: We retrospectively analyzed the cases of 46 pancreatic cancer patients aged ≥80 years (median 83, range 80-97) treated with definitive C-ion RT in 2007-2018 at our institute. RESULTS: Twenty-five patients (54%) had resectable or borderline-resectable disease; none underwent surgery (because of medical reasons, e.g., age, multiple comorbidities). C-ion RT was delivered with a median dose of 55.2 Gy (RBE) in 12 fractions. The survivors' median follow-up period was 43 (range 19-76) months. The entire cohort's median overall survival (OS) was 15 (95%CI: 14-22) months with a 3-year OS of 20% (95%CI: 11%-35%). On both univariate and multivariate analyses, baseline CA19-9 remained the significant independent OS prognostic factor (p = 0.032). The 3-year local control rate for all patients was 34% (95%CI: 19%-53%). Local failure (n = 25, 54%) was as common as distant relapse (n = 26, 57%); 33% of the patients experienced both local and systemic failure. About 15% underwent re-C-ion RT for infield recurrence; they achieved a median 22-month OS. No patients exhibited grade ≥3 severe acute or late toxicities (including those who received re-C-ion RT). CONCLUSIONS: C-ion RT in octogenarians with pancreatic cancer showed promising outcomes with acceptable acute and late toxicities and can be considered a reasonable alternative to radical surgery.
Assuntos
Radioterapia com Íons Pesados , Neoplasias Pancreáticas , Idoso , Idoso de 80 Anos ou mais , Radioterapia com Íons Pesados/efeitos adversos , Humanos , Recidiva Local de Neoplasia , Octogenários , Neoplasias Pancreáticas/etiologia , Neoplasias Pancreáticas/radioterapia , Estudos Retrospectivos , Neoplasias PancreáticasRESUMO
This technical report introduces the utility of iodine paste markers using endodontic materials for the accurate contouring of mucosal lesions of oral mucosal melanoma, which are difficult to delineate on imaging during the planning of carbon-ion radiation therapy (CIRT). The patient had a primary oral mucosal melanoma located in the palatal mucosa without palatal or maxillary bone invasion. A dental root canal filling material, which is a calcium hydroxide/iodoform nonhardenable paste, was used as a marker. We first performed treatment-planning computed tomography (CT) without an iodine paste marker for mucosal lesions. Subsequently, we placed an iodine paste marker on the palatal mucosal lesion to accurately delineate the mucosal lesions of the palate. Finally, we obtained a reference CT image with an iodine paste marker. Computed tomography without the marker was fused to the reference CT with markers during treatment planning, and the gross tumor volume was contoured. Thereafter, CIRT was delivered without markers. During CIRT, expected acute mucositis was observed in the area of the planning target volume, including melanosis, in accordance with the dose distribution. The use of iodine paste markers for localized mucosal lesions, which are difficult to delineate on CT and magnetic resonance imaging, may be useful for accurately contouring gross tumor volumes on treatment-planning CT.
Assuntos
Iodo , Melanoma , Humanos , Imageamento por Ressonância Magnética/métodos , Melanoma/diagnóstico por imagem , Melanoma/radioterapia , Planejamento da Radioterapia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodosRESUMO
In this study, the stopping-power ratios (SPRs) of mouthpiece materials were measured and the errors in the predicted SPRs based on conversion table values were further investigated. The SPRs of the five mouthpiece materials were predicted from their computed tomography (CT) numbers using a calibrated conversion table. Independently, the SPRs of the materials were measured from the Bragg peak shift of a carbon-ion beam passing through the materials. The errors in the SPRs of the materials were determined as the difference between the predicted and measured values. The measured SPRs (errors) of the Nipoflex 710™ and Bioplast™ ethylene-vinyl acetate copolymers (EVAs) were 0.997 (0.023) and 0.982 (0.007), respectively. The SPRs of the vinyl silicon impression material, light-curable resin, and bis-acrylic resin were 1.517 (0.134), 1.161 (0.068), and 1.26 (0.101), respectively. Among the five tested materials, the EVAs had the lowest SPR errors, indicating the highest human-tissue equivalency.
Assuntos
Neoplasias de Cabeça e Pescoço , Terapia com Prótons , Humanos , Imagens de Fantasmas , Planejamento da Radioterapia Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodosRESUMO
BACKGROUND: This study aimed to assess the safety and efficacy of carbon-ion radiotherapy (CIRT) for salvage of previously X-ray-irradiated (XRT) locally recurrent rectal cancer (LRRC). METHODS: Between September 2005 and December 2017, 77 patients with LRRC were treated with CIRT re-irradiation. All the patients had received prior XRT with a median dose of 50.0 Gy (range 20-74 Gy), principally for neoadjuvant or adjuvant recurrence prophylaxis in 34 patients and for recurrence in 43 patients. The total CIRT dose of 70.4 Gy (RBE) (gray relative biologic effectiveness) was administered in 16 fixed fractions during 4 weeks (4.4 Gy [RBE] per fraction). RESULTS: All the patients completed the scheduled treatment course. None of the patients received resection after CIRT. Acute grade 3 toxicities occurred for eight patients (10 %), including five grade 3 pelvic infections (2 involving pain and 1 involving neuropathy). Late grade 3 toxicities occurred for 16 patients (21 %): 13 with late grade 3 pelvic infections, 9 with gastrointestinal toxicity, 1 with skin toxicity, 2 with pain, and 4 with neuropathy. No grade 4+ toxicity was noted. The overall local control rates (infield + out-of-field recurrence) were 69 % at 3 years and 62 % at 5 years. In the planning target volume (PTV), the infield recurrence rates were 90 % and 87 % respectively. The control rates for regional recurrence were 85 % at 3 years and 81 % at 5 years. The median overall survival time was 47 months. The survival rates were 61 % at 3 years and 38 % at 5 years. CONCLUSION: Carbon-ion re-irradiation of previously X-ray-irradiated locally recurrent rectal cancer appears to be safe and effective, providing good local control and survival advantage without unacceptable morbidity.
Assuntos
Radioterapia com Íons Pesados , Neoplasias Retais , Radioterapia com Íons Pesados/efeitos adversos , Humanos , Neoplasias Retais/radioterapiaRESUMO
For hypo-fractionated multi-ion therapy (HFMIT), the stochastic microdosimetric kinetic (SMK) model had been developed to estimate the biological effectiveness of radiation beams with wide linear energy transfer (LET) and dose ranges. The HFMIT will be applied to radioresistant tumors with oxygen-deficient regions. The response of cells to radiation is strongly dependent on the oxygen condition in addition to radiation type, LET and absorbed dose. This study presents an adaptation of the SMK model to account for oxygen-pressure dependent cell responses, and develops the oxygen-effect-incorporated stochastic microdosimetric kinetic (OSMK) model. In the model, following assumptions were made: the numbers of radiation-induced sublethal lesions (double-strand breaks) are reduced due to lack of oxygen, and the numbers of oxygen-mediated lesions are reduced for radiation with high LET. The model parameters were determined by fitting survival data under aerobic and anoxic conditions for human salivary gland tumor cells and V79 cells exposed to helium-, carbon-, and neon-ion beams over the LET range of 18.5-654.0 keVµm-1. The OSMK model provided good agreement with the experimental survival data of the cells with determination coefficients >0.9. In terms of oxygen enhancement ratio, the OSMK model reproduced the experimental data behavior, including slight dependence on particle type at the same LET. The OSMK model was then implemented into the in-house treatment planning software for the HFMIT to validate its applicability in clinical practice. A treatment plan with helium- and neon-ion beams was made for a pancreatic cancer case assuming an oxygen-deficient region within the tumor. The biological optimization based on the OSMK model preferentially placed the neon-ion beam to the hypoxic region, while it placed both helium- and neon-ion beams to the surrounding normoxic region. The OSMK model offered the accuracy and usability required for hypoxia-based biological optimization in HFMIT treatment planning.
Assuntos
Hélio , Neoplasias Pancreáticas , Hélio/uso terapêutico , Humanos , Hipóxia , Íons , Neônio/uso terapêutico , Oxigênio/uso terapêutico , Neoplasias Pancreáticas/tratamento farmacológico , Eficiência Biológica RelativaRESUMO
Heavy-ion radiotherapy (RT) is a kind of particle RT, and carbon-ion beam constitutes the primary delivery method of heavy-ion RT. Unlike the conventional photon modalities, particle RT, in particular carbon-ion radiotherapy (CIRT), offers unique physical and biological advantages. Particle therapy allows for substantial dose delivery to tumors with minimal surrounding tissue damage. In addition, CIRT in particular possesses biological advantages such as inducing increased double-strand breaks in DNA structures, causing irreversible cell damage independently of cell cycle or oxygenation, more so than proton or photon. It can be expected that CIRT is effective on radioresistant cancers such as colorectal cancers (CRCs). We introduced the results of CIRT for local recurrent rectal cancer, lung metastasis, liver metastasis, and lymph node metastasis.
RESUMO
BACKGROUND/AIM: We aimed to investigate the dosimetric effects of a spacer placed between the pancreas and surrounding gastrointestinal structures in intensity-modulated radiation therapy (IMRT) planning to provide more effective radiation therapy for locally advanced pancreatic cancer (LAPC). PATIENTS AND METHODS: Treatment planning was performed for six patients with LAPC based on computed tomography images without spacers and with 5-mm or 10-mm spacers virtually inserted under the supervision of a hepatobiliary pancreatic surgeon. The prescription dose was 63 Gy in 28 fractions. RESULTS: With the exception of one case of pancreatic head cancer, planning target volume receiving ≥95% of the prescribed dose (PTV V95) was achieved by 90% or more by inserting a spacer, and by 95% or more in all 3 cases of pancreatic body and tail cancer by inserting a 10-mm spacer. CONCLUSION: IMRT with appropriate spacer placement may help provide high-dose treatment for LAPC and improve associated patient outcomes.
Assuntos
Tratamentos com Preservação do Órgão/instrumentação , Neoplasias Pancreáticas/radioterapia , Planejamento da Radioterapia Assistida por Computador , Radioterapia , Feminino , Humanos , Masculino , Metástase Neoplásica , Estadiamento de Neoplasias , Tratamentos com Preservação do Órgão/métodos , Neoplasias Pancreáticas/diagnóstico , Neoplasias Pancreáticas/mortalidade , Radioterapia/instrumentação , Radioterapia/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Estudos Retrospectivos , Tomografia Computadorizada por Raios X , Resultado do TratamentoRESUMO
BACKGROUND AND PURPOSE: Patients who receive carbon-ion radiotherapy (C-ion RT) for primary pancreatic cancer may experience locoregional recurrence; however, the treatment options for such patients are limited. We aimed to investigate the feasibility and efficacy of carbon-ion re-irradiation for patients with pancreatic cancer who experienced recurrence after initial C-ion RT. MATERIALS AND METHODS: Twenty-one patients with recurrent pancreatic cancer who underwent repeat C-ion RT between December 2010 and November 2016 at our institute were retrospectively evaluated. The sites of post-initial C-ion RT failure were in-field central in 16 patients (76.2%) and marginal in 5 (23.8%). The median doses of initial and repeat C-ion RT were both 52.8 Gy (relative biological effectiveness [RBE]). Thirteen patients (61.9%) received concurrent chemotherapy with re-irradiation, while 11 (52.4%) received adjuvant chemotherapy. RESULTS: The median follow-up period after re-irradiation was 11 months. The 1-year local control, progression-free survival, and overall survival rates were 53.5%, 24.5%, and 48.7%, respectively. Toxicity data was obtained from the patients' charts. Only 1 patient (4.8%) developed grade 3 acute toxicities and none developed grade ≥3 late toxicities. Univariate analysis indicated that patients who received adjuvant chemotherapy had significantly improved local control rates compared with those who did not; the 1-year local control rates were 80.0% and 0.0%, respectively (P = 0.0469). CONCLUSION: Repeating C-ion RT may be a reasonable option with tolerable toxicity for patients with recurrent pancreatic cancers. Adjuvant chemotherapy appears to improve the local control rate. This is the first study to examine re-irradiation using C-ion for recurrent pancreatic cancer after initial C-ion RT.