Carbon-ion radiotherapy for clear cell odontogenic carcinomas.

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.

Reduced Risk of Severe Radiation-Induced Lymphopenia in Carbon Ion Radiation Therapy for Locally Advanced Pancreatic Cancer: A Comparative Analysis of Carbon Versus Photon Therapy.

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.

Outcomes of definitive carbon-ion radiotherapy for cT1bN0M0 esophageal squamous cell carcinoma.

BACKGROUND: A recent phase I/II study determined the optimal dose of definitive carbon-ion radiotherapy (CIRT) for cT1bN0M0 esophageal cancer. This study aimed to further confirm the efficacy and feasibility of the recommended dose fractionation of CIRT with long-term follow-up results in a larger sample size. METHODS: This single center retrospective study evaluated patients with cT1bN0M0 esophageal squamous cell carcinoma treated with the recommended dose fractionation of 50.4 Gy relative biological effectiveness in 12 fractions, between 2012 and 2022. RESULTS: Thirty-eight patients underwent CIRT at our hospital. Although eight (21.1%) patients were older than 80 years, 15 (39.5%) had high surgical risk, and seven (18.4%) were at high risk for chemotherapy, all patients underwent CIRT as scheduled. Grade 3 esophagitis occurred in eight (21.1%) patients and grade 3 pneumonia in one (2.6%) patient in this study, but no grade 4 adverse events occurred. The only grade 3 late adverse event was pneumonia in one patient (2.6%). The 5-year overall survival rate, local control rate, and disease-free survival rates were 76.6% (95% CI, 90.9-62.4), 74.9% (95% CI, 90.7-59.0), and 66.4% (95% CI, 83.3-49.5), respectively. Additionally, post CIRT recurrence was as follows: seven (18.4%) patients had recurrence in another part of the esophagus, three (7.9%) in the primary site, three (7.9%) in lymph nodes outside the irradiated area, and one (2.6%) patient had liver metastasis. CONCLUSIONS: Our study demonstrates that CIRT using the recommended dose fractionation is feasible and effective for cT1bN0M0 esophageal squamous cell carcinoma.

Dose-averaged LET optimized carbon-ion radiotherapy for head and neck cancers.

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.