Abstract
Simple SummaryThere was no reports about the risk factors of high dose single-fraction carbon-ion radiotherapy. Although there were only small number of patients with symptomatic radiation pneumonitis after this treatment, we showed that the risk factors of radiation pneumonitis include the dose–volume parameter.There are no studies on the risk factors of radiation pneumonitis (RP) after carbon-ion radiotherapy at a dose of 50 Gy (relative biological effectiveness (RBE)) in a single fraction. The objective of this study was to identify factors associated with RP after radiotherapy, including dose–volume parameters. Ninety-eight patients without a history of thoracic radiotherapy who underwent treatment for solitary lung tumors between July 2013 and April 2016 were retrospectively analyzed. Treatment was planned using Xio-N. The median follow-up duration was 53 months, and the median clinical target volume was 32.3 mL. Three patients developed grade 2 RP, and one patient developed grade 3 interstitial pneumonitis. None of the patients developed grade 4 or 5 RP. The dose-volume parameters of the normal lung irradiated at least with 5–30 Gy (RBE), and the mean lung dose was significantly lower in patients with grade 0–1 RP than in those with grade 2–3 RP. Pretreatment with higher SP-D and interstitial pneumonitis were significant factors for the occurrence of symptomatic RP. The present study showed a certain standard for single-fraction carbon-ion radiotherapy that does not increase the risk of RP; however, further validation studies are needed.
Highlights
In 2018, 2.1 million new lung cancer cases were detected, accounting for approximately 12% of all new cancer cases, along with a high mortality rate, accounting for approximately one in five (18.4%) cancer-related deaths
We identified 104 patients with lung tumors who received single-fraction passive carbon-ion radiotherapy (CIRT) (50 Gy (RBE)) between June 2013 and April 2016
Six patients were excluded because of a history of thoracic radiotherapy received before single-fraction CIRT
Summary
In 2018, 2.1 million new lung cancer cases were detected, accounting for approximately 12% of all new cancer cases, along with a high mortality rate, accounting for approximately one in five (18.4%) cancer-related deaths. Surgery is the first choice of treatment for early-stage lung cancer [2]. Many patients are medically contraindicated to undergo surgical resection or refuse to undergo surgery because of poor performance status, older age, and complications. In such patients, stereotactic body radiotherapy (SBRT) is recommended as a radical treatment [2]. A recent study based on the National Cancer Database revealed that SBRT is associated with improved overall survival compared to that with no treatment in patients with early-stage non-small cell lung cancer (hazard ratio: 0.56) [6]. SBRT is an important treatment choice for patients with lung cancer, especially for inoperable patients
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