High-dose proton therapy and carbon-ion therapy for stage I nonsmall cell lung cancer

Long-term survival outcomes and quality of life of image-guided proton therapy for operable stage I non-small cell lung cancer: A phase 2 study

BACKGROUND AND PURPOSE

This study evaluated long-term efficacy, safety, and changes in quality of life (QOL) of patients after image-guided proton therapy (IGPT) for operable stage I non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

This single-institutional prospective phase 2 study enrolled patients with operable histologically confirmed stage IA or IB NSCLC (7th edition of UICC). The prescribed dose was 66 Gy relative biological effectiveness equivalents (GyRBE) in 10 fractions for peripheral lesions, or 72.6 GyRBE in 22 fractions for central lesions. The primary endpoint was the 3-year overall survival (OS). The secondary endpoints included disease control, toxicity, and changes in QOL score.

RESULTS

We enrolled 43 patients (median age: 68 years; range, 47-79 years) between July 2013 to January 2021, of whom 41 (95 %) had peripheral lesions and 27 (63 %) were stage IA. OS, local control, and progression-free survival rates were 95 % (95 % CI: 83-99), 95 % (82-99), and 86 % (72-94), respectively, at 3 years, and 83 % (66-92), 95 % (82-99), and 77 % (60-88), respectively, at 7 years. Four patients (9 %) developed grade 2, and one patient (2 %) developed grade 3 radiation pneumonitis. No other grade 3 or higher adverse events were observed. In the QOL analysis, global QOL remained favorable; however, approximately 40 % of patients reported dyspnea at 3 and 24 months.

CONCLUSION

Our findings suggest that IGPT provides effective disease control and survival in operable stage I NSCLC, particularly for peripheral lesions. Moreover, toxicity associated with IGPT was minimal, and patients reported favorable QOL.

A meta-analysis comparing efficacy and safety between proton beam therapy versus carbon ion radiotherapy

BACKGROUND

This study aimed to compare the outcomes of proton beam therapy (PBT) and carbon ion radiotherapy (CIRT) by a systematic review and meta-analysis of the existing clinical evidence.

METHODS

A systematic literature search was performed to identify studies comparing the clinical outcomes of PBT and CIRT. The included studies were required to report oncological outcomes (local control [LC], progression-free survival [PFS], or overall survival [OS]) or adverse events.

RESULTS

Eighteen articles comprising 1857 patients (947 treated with PBT and 910 treated with CIRT) were included in the analysis. The pooled analysis conducted for the overall population yielded average hazard ratios of 0.690 (95% confidence interval (CI), 0.493-0.967, p = 0.031) for LC, 0.952 (95% CI, 0.604-1.500, p = 0.590) for PFS, and 1.183 (0.872-1.607, p = 0.281) for OS with reference to CIRT. The subgroup analyses included patients treated in the head and neck, areas other than the head and neck, and patients with chordomas and chondrosarcomas. These analyses revealed no significant differences in most outcomes, except for LC in the subgroup of patients treated in areas other than the head and neck. Adverse event rates were comparable in both groups, with an odds ratio (OR) of 1.097 (95% CI, 0.744-1.616, p = 0.641). Meta-regression analysis for possible heterogeneity did not demonstrate a significant association between treatment outcomes and the ratio of biologically effective doses between modalities.

CONCLUSION

This study highlighted the comparability of PBT and CIRT in terms of oncological outcomes and adverse events.

Hypoxia Modulates Radiosensitivity and Response to Different Radiation Qualities in A549 Non-Small Cell Lung Cancer (NSCLC) Cells

Hypoxia-induced radioresistance reduces the efficacy of radiotherapy for solid malignancies, including non-small cell lung cancer (NSCLC). Cellular hypoxia can confer radioresistance through cellular and tumor micro-environment adaptations. Until recently, studies evaluating radioresistance secondary to hypoxia were designed to maintain cellular hypoxia only before and during irradiation, while any handling of post-irradiated cells was carried out in standard oxic conditions due to the unavailability of hypoxia workstations. This limited the possibility of simulating in vivo or clinical conditions in vitro. The presence of molecular oxygen is more important for the radiotoxicity of low-linear energy transfer (LET) radiation (e.g., X-rays) than that of high-LET carbon (12C) ions. The mechanisms responsible for 12C ions' potential to overcome hypoxia-induced radioresistance are currently not fully understood. Therefore, the radioresistance of hypoxic A549 NSCLC cells following exposure to X-rays or 12C ions was investigated along with cell cycle progression and gene expression by maintaining hypoxia before, during and after irradiation. A549 cells were incubated under normoxia (20% O2) or hypoxia (1% O2) for 48 h and then irradiated with X-rays (200 kV) or 12C ions (35 MeV/n, LET ~75 keV/µm). Cell survival was evaluated using colony-forming ability (CFA) assays immediately or 24 h after irradiation (late plating). DNA double-strand breaks (DSBs) were analyzed using γH2AX immunofluorescence microscopy. Cell cycle progression was determined by flow cytometry of 4',6-diamidino-2-phenylindole-stained cells. The global transcription profile post-irradiation was evaluated by RNA sequencing. When hypoxia was maintained before, during and after irradiation, hypoxia-induced radioresistance was observed only in late plating CFA experiments. The killing efficiency of 12C ions was much higher than that of X-rays. Cell survival under hypoxia was affected more strongly by the timepoint of plating in the case of X-rays compared to 12C ions. Cell cycle arrest following irradiation under hypoxia was less pronounced but more prolonged. DSB induction and resolution following irradiation were not significantly different under normoxia and hypoxia. Gene expression response to irradiation primarily comprised cell cycle regulation for both radiation qualities and oxygen conditions. Several PI3K target genes involved in cell migration and cell motility were differentially upregulated in hypoxic cells. Hypoxia-induced radioresistance may be linked to altered cell cycle response to irradiation and PI3K-mediated changes in cell motility and migration in A549 cells rather than less DNA damage or faster repair.

Clinical impact of spacer placement surgery with expanded polytetrafluoroethylene sheet for particle therapy

BACKGROUND

Spacer placement surgery is useful in particle therapy (PT) for patients with abdominopelvic malignant tumors located adjacent to the gastrointestinal tract. This study aimed to assess the safety, efficacy, and long-term outcomes of spacer placement surgery using an expanded polytetrafluoroethylene (ePTFE) spacer.

METHODS

This study included 131 patients who underwent ePTFE spacer placement surgery and subsequent PT between September 2006 and June 2019. The overall survival (OS) and local control (LC) rates were calculated using Kaplan-Meier method. Spacer-related complications were classified according to the National Cancer Institute Common Terminology Criteria for Adverse Events (version 5.0).

RESULTS

The median follow-up period after spacer placement surgery was 36.8 months. The 3-year estimated OS and LC rates were 60.5% and 76.5%, respectively. A total of 130 patients (99.2%) were able to complete PT. Spacer-related complications of ≥ grade 3 were observed in four patients (3.1%) in the acute phase and 13 patients (9.9%) in the late phase. Ten patients (7.6%) required removal of the ePTFE spacer.

CONCLUSIONS

Spacer placement surgery using an ePTFE spacer for abdominopelvic malignant tumors is technically feasible and acceptable for subsequent PT. However, severe spacer-related late complications were observed in some patients. Since long-term placement of a non-absorbable ePTFE spacer is associated with risks for morbidity and infection, careful long-term follow-up and prompt therapeutic intervention are essential when complications associated with the ePTFE spacer occur.

TRIAL REGISTRATION

retrospectively registered.

Intensity-modulated radiotherapy for the management of primary and recurrent chordomas: a retrospective long-term follow-up study

Background

Chordomas have a high risk of recurrence. Radiotherapy (RT) is required as adjuvant therapy after resection. Sufficient radiation doses for local control (LC) can be achieved using either particle therapy, if this technology is available and feasible, or intensity-modulated radiotherapy.

Materials and methods

57 patients (age, 11.8-81.6 years) with chordomas of the skull base, spine and pelvis who received photon radiotherapy between 1995 and 2017 were enrolled in the study. Patients were treated at the time of initial diagnosis (68.4%) or during recurrence (31.6%). 44 patients received adjuvant radiotherapy and 13 received definitive radiotherapy. The median total dose to the physical target volume was 70 Gy equivalent dose in 2 Gy fractions (EQD2) (range: 54.7-82.5) in 22-36 fractions.

Results

LC was 76.4%, 58.4%, 46.7% and 39.9% and overall survival (OS) was 98.3%, 89%, 76.9% and 47.9% after 1, 3, 5 and 10 years, respectively, with a median follow-up period of 6.5 years (range, 0.5-24.3 years). Age, dose and treatment concept (post-operative or definitive) were significant prognostic factors for OS. Primary treatment, macroscopic tumour at RT and size of the irradiated volume were statistically significant prognostic factors for LC.

Conclusion

Photon treatment is a safe and effective treatment for chordomas if no particle therapy is available. The best results can be achieved against primary tumours if the application of curative doses is possible due to organs at risk in direct proximity. We recommend high-dose radiotherapy, regardless of the resection status, as part of the initial treatment of chordoma, using the high conformal radiation technique if particle therapy is not feasible.

METTL3-mediated m6A mRNA contributes to the resistance of carbon-ion radiotherapy in non-small-cell lung cancer

Lung cancer is one of the leading causes of death among cancer patients worldwide. Carbon-ion radiotherapy is a radical nonsurgical treatment with high local control rates and no serious adverse events. N6-methyladenosine (m6A) modification is one of the most common chemical modifications in eukaryotic messenger RNA (mRNA) and has important effects on the stability, splicing, and translation of mRNAs. Recently, the regulatory role of m6A in tumorigenesis has been recognized more and more. However, the dysregulation of m6A and its role in carbon-ion radiotherapy of non-small-cell lung cancer (NSCLC) remains unclear. In this study, we found that the level of methyltransferase-like 3 (METTL3) and its mediated m6A modification were elevated in NSCLC cells with carbon-ion radiotherapy. Knockdown of METTL3 in NSCLC cells impaired proliferation, migration, and invasion in vitro and in vivo. Moreover, we found that METTL3-mediated m6A modification of mRNA inhibited the decay of H2A histone family member X (H2AX) mRNA and enhanced its expression, which led to enhanced DNA damage repair and cell survival.

The Role of Hypofractionation in Proton Therapy

Hypofractionated radiotherapy is an attractive approach for minimizing patient burden and treatment cost. Technological advancements in external beam radiotherapy (EBRT) delivery and image guidance have resulted in improved targeting and conformality of the absorbed dose to the disease and a reduction in dose to healthy tissue. These advances in EBRT have led to an increasing adoption and interest in hypofractionation. Furthermore, for many treatment sites, proton beam therapy (PBT) provides an improved absorbed dose distribution compared to X-ray (photon) EBRT. In the past 10 years there has been a notable increase in reported clinical data involving hypofractionation with PBT, reflecting the interest in this treatment approach. This review will discuss the reported clinical data and radiobiology of hypofractionated PBT. Over 50 published manuscripts reporting clinical results involving hypofractionation and PBT were included in this review, ~90% of which were published since 2010. The most common treatment regions reported were prostate, lung and liver, making over 70% of the reported results. Many of the reported clinical data indicate that hypofractionated PBT can be well tolerated, however future clinical trials are still needed to determine the optimal fractionation regime.

Assessment of Proton Beam Therapy Use Among Patients With Newly Diagnosed Cancer in the US, 2004-2018

IMPORTANCE

Proton beam therapy (PBT) is a potentially superior technology to photon radiotherapy for tumors with complex anatomy, those surrounded by sensitive tissues, and childhood cancers.

OBJECTIVE

To assess patterns of use of PBT according to the present American Society of Radiation Oncology (ASTRO) clinical indications in the US.

DESIGN, SETTING, AND PARTICIPANTS

Individuals newly diagnosed with cancer between 2004 and 2018 were selected from the National Cancer Database. Data analysis was performed from October 4, 2021, to February 22, 2022. ASTRO's Model Policies (2017) were used to classify patients into group 1, for which health insurance coverage for PBT treatment is recommended, and group 2, for which coverage is recommended only if additional requirements are met.

MAIN OUTCOMES AND MEASURES

Use of PBT.

RESULTS

Of the 5 919 368 patients eligible to receive PBT included in the study, 3 206 902 were female (54.2%), and mean (SD) age at diagnosis was 62.6 (12.3) years. Use of PBT in the US increased from 0.4% in 2004 to 1.2% in 2018 (annual percent change [APC], 8.12%; P < .001) due to increases in group 1 from 0.4% in 2010 to 2.2% in 2018 (APC, 21.97; P < .001) and increases in group 2 from 0.03% in 2014 to 0.1% in 2018 (APC, 30.57; P < .001). From 2010 to 2018, among patients in group 2, PBT targeted to the breast increased from 0.0% to 0.9% (APC, 51.95%), and PBT targeted to the lung increased from 0.1% to 0.7% (APC, 28.06%) (P < .001 for both). Use of PBT targeted to the prostate decreased from 1.4% in 2011 to 0.8% in 2014 (APC, -16.48%; P = .03) then increased to 1.3% in 2018 (APC, 12.45; P < .001). Most patients in group 1 treated with PBT had private insurance coverage in 2018 (1039 [55.4%]); Medicare was the most common insurance type among those in group 2 (1973 [52.5%]).

CONCLUSIONS AND RELEVANCE

The findings of this study show an increase in the use of PBT in the US between 2004 to 2018; prostate was the only cancer site for which PBT use decreased temporarily between 2011 and 2014, increasing again between 2014 and 2018. These findings may be especially relevant for Medicare radiation oncology coverage policies.

Outcomes of proton therapy for non-small cell lung cancer in patients with interstitial pneumonia

Background

Interstitial pneumonia (IP) is a disease with a poor prognosis. In addition, IP patients are more likely to develop lung cancer. Since IP patients frequently develop toxicities during cancer treatment, minimally invasive cancer treatment is warranted for such patients to maintain their quality of life. This study retrospectively investigated the efficacy and safety of proton therapy (PT) for non-small cell lung cancer (NSCLC) in patients with IP.

Methods

Twenty-nine NSCLC patients with IP were treated with PT between September 2013 and December 2019. The patients had stage IA to IIIB primary NSCLC. Ten of the 29 patients exhibited the usual interstitial pneumonia pattern. The prescribed dose was 66–74 Grays (relative biological effectiveness) in 10–37 fractions.

Results

The median follow-up period was 21.1 months [interquartile range (IQR), 15.6–37.3] for all patients and 37.2 months (IQR, 24.0–49.9) for living patients. The median patient age was 77 years (IQR, 71–81). The median planning target volume was 112.0 ml (IQR, 56.1–246.3). The 2-year local control, progression-free survival, and overall survival rates were 85% (95% confidence interval: 57–95), 30% (15–47), and 45% (26–62), respectively. According to the Common Terminology Criteria for Adverse Events (version 4.0), grade 3 acute radiation pneumonitis (RP) was observed in 1 patient. Two patients developed grade 3 late RP, but no other patients experienced serious toxicities. The patients’ quality of life (European Organization for Research and Treatment of Cancer QLQ-C30 and QLQ-LC13 and SF-36) scores had not changed after 3 months.

Conclusions

PT may be a relatively safe treatment for NSCLC patients with IP, without deteriorating quality of life scores within 3 months.

Stereotactic radiotherapy for early stage non-small cell lung cancer: current standards and ongoing research

Stereotactic body radiation therapy (SBRT) allows for the non-invasive and precise delivery of ablative radiation dose. The use and availability of SBRT has increased rapidly over the past decades. SBRT has been proven to be a safe, effective and efficient treatment for early stage non-small cell lung cancer (NSCLC) and is presently considered the standard of care in the treatment of medically or functionally inoperable patients. Evidence from prospective randomized trials on the optimal treatment of patients deemed medically operable remains owing, as three trials comparing SBRT to surgery in this cohort were terminated prematurely due to poor accrual. Yet, SBRT in early stage NSCLC is associated with favorable toxicity profiles and excellent rates of local control, prompting discussion in regard of the treatment of medically operable patients, where the standard of care currently remains surgical resection. Although local control in early stage NSCLC after SBRT is high, distant failure remains an issue, prompting research interest to the combination of SBRT and systemic treatment. Evolving advances in SBRT technology further facilitate the safe treatment of patients with medically or anatomically challenging situations. In this review article, we discuss international guidelines and the current standard of care, ongoing clinical challenges and future directions from the clinical and technical point of view.

Proton beam radiotherapy for patients with early-stage and advanced lung cancer: a narrative review with contemporary clinical recommendations

Although lung cancer rates are decreasing nationally, lung cancer remains the leading cause of cancer related death. Despite advancements in treatment and technology, overall survival (OS) for lung cancer remains poor. Proton beam therapy (PBT) is an advanced radiation therapy (RT) modality for treatment of lung cancer with the potential to achieve dose escalation to tumor while sparing critical structures due to higher target conformality. In early and late-stage non-small cell lung cancer (NSCLC), dosimetric studies demonstrated reduced doses to organs at risk (OARs) such as the lung, spinal cord, and heart, and clinical studies report limited toxicities with PBT, including hypofractionated regimens. In limited-stage SCLC, studies showed that regimens chemo RT including PBT were well tolerated, which may help optimize clinical outcomes. Improved toxicity profiles may be beneficial in post-operative radiotherapy, for which initial dosimetric and clinical data are encouraging. Sparing of OARs may also increase the proportion of patients able to complete reirradiation for recurrent disease. However, there are various challenges of using PBT including a higher financial burden on healthcare and limited data supporting its cost-effectiveness. Further studies are needed to identify subgroups that benefit from PBT based on prognostic factors, and to evaluate PBT combined with immunotherapy, in order to elucidate the benefit that PBT may offer future lung cancer patients.

Surgical spacer placement for proton radiotherapy in locally advanced pancreatic body and tail cancers: initial clinical results

Background

Particle radiotherapy has increasingly gained acceptance for locally advanced pancreatic cancers owing to superior tumor conformity and dosimetry compared to conventional photon radiotherapy. However, the close proximity of the pancreas to the stomach and duodenum leads to radiation-induced gastrointestinal toxicities, which hinder the delivery of curative doses to the tumor. To overcome this problem, a surgical spacer was placed between the tumor and gastrointestinal tract, and subsequent proton radiotherapy was performed in this study.

Methods

Data from 9 patients who underwent surgical spacer placement and subsequent proton radiotherapy were analyzed. The safety and feasibility of the spacer placement surgery were evaluated; the impact of the spacer on dosimetry was also assessed using dose volume histogram (DVH) analyses, before and after surgical spacer placement.

Results

Surgical spacer placement and subsequent proton radiotherapy were successfully completed in all cases. Surgical spacer placement significantly improved the dose intensity covering 95%, mean, and minimum doses for the gross tumor volume, and the clinical and planning target volume based on the DVH, while respecting the dose constraints of the gastrointestinal tract. Based on the Common Terminology Criteria for Adverse Events, two patients (22.2%) developed gastrointestinal ulcer (Grade 2) at 1 and 35 months, and one patient (11.1%) developed gastric perforation (Grade 4) at 4 months after proton radiotherapy.

Conclusions

Surgical spacer placement in the locally advanced pancreatic body and tail cancers is relatively safe and technically feasible. Comparing radiation plans, surgical spacer placement seems to improve the dose distribution in the locally advanced pancreatic body and tail cancers, which are close to the gastrointestinal tract.

Long Term Results of Single-Fraction Carbon-Ion Radiotherapy for Non-small Cell Lung Cancer

Simple Summary

There were no reports on long-term results of single-fraction passive carbon-ion radiotherapy in patients with early-stage non-small cell lung cancer. We showed that this treatment was not inferior compared to stereotactic body radiotherapy or proton beam therapy with no ≥grade 2 pneumonitis. This study suggests that single-fraction passive carbon-ion radiotherapy can serve as an alternate treatment for patients with early-stage non-small cell lung cancer, especially in medically inoperable patients.

Abstract

Background: The purpose of the present study was to evaluate the efficacy and safety of single-fraction carbon-ion radiotherapy (CIRT) in patients with non-small cell lung cancer. Methods: Patients with histologically confirmed non-small cell lung cancer, stage T1-2N0M0, and treated with single-fraction CIRT (50Gy (relative biological effectiveness)) between June 2011 and April 2016 were identified in our database and retrospectively analyzed. Toxicity was evaluated using the Common Terminology Criteria for Adverse Events version 4.0. Results: The study included 57 patients, 22 (38.6%) of whom had inoperable cancer. The median age was 75 years (range: 42–94 years), and the median follow-up time was 61 months (range: 6–97 months). The 3- and 5-year overall survival rates were 91.2% and 81.7%, respectively. All survivors were followed up for more than three years. The 3- and 5-year local control rates were 96.4% and 91.8%, respectively. No case of ≥ grade 2 pneumonitis was recorded. Conclusions: This study suggests that single-fraction CIRT for T1-2N0M0 non-small cell lung cancer patients is feasible and can be considered as one of the treatment choices, especially in medically inoperable patients.

Clinical Outcomes of Proton Beam Therapy for Ground-Glass Opacity-Type Lung Cancer

Purpose

Surgery is the standard treatment for early-stage non-small cell lung cancer (NSCLC), including ground-glass opacity (GGO)-type lung cancer. However, some patients are inoperable or refuse to undergo surgery. To explore whether proton beam therapy (PBT) can be an alternative to surgical resection in these patients, this study aimed to examine the retrospective treatment outcomes of patients with GGO-type lung cancer who underwent PBT.

Patients and Methods

Patients with stage I NSCLC and GGOs who underwent PBT at the Medipolis Proton Therapy and Research Center (Kagoshima, Japan) between April 2011 and September 2015 were included. Patients were treated with a total dose of 66 GyE delivered in 10 fractions. Survival curves were calculated using the Kaplan–Meier method, and treatment-related adverse events (AEs) were assessed.

Results

A total of 48 patients (median age: 70.9 ± 9.2 years; men: 54.2%) were analyzed, among whom 53 tumors were observed. The 3-year overall survival rate after PBT was 91.7% (95% confidence interval [CI], 79.3–96.8%), the 3-year disease-free survival rate was 85.4% (95% CI: 71.8–92.8%), and the 3-year local control rate among 53 tumors was 92.5% (95% CI: 81.1–97.1%). During the 3-year follow-up period, 4 patients died, and 3 survived despite recurrence or metastasis. Common AEs were radiation pneumonitis (89.6%), rib fracture (27.1%), and cough (27.1%). None of the patients developed grade ≥3 treatment-related AEs.

Conclusion

The results of this study suggest that PBT may be a promising alternative for patients with GGO-type lung cancer when surgical resection is not feasible, with excellent survival outcomes and tolerable treatment-related AEs.

Proton therapy for non-small cell lung cancer: the road ahead

Proton therapy is an evolving radiotherapy modality with indication for numerous cancer types. With the benefits of reducing dose and sparing normal tissue, protons offer a clear physical and dosimetric advantage over photon radiotherapy for many patients. However, its impact on one type of disease, non-small cell lung cancer (NSCLC), is still not fully understood. Our review aims to highlight the data for using proton therapy in NSCLC, with a focus on the clinical data-or lack thereof-supporting proton treatment for early and advanced stage disease. In evaluating these data, we consider how future directions and advances in proton technology give rise for hope in defining a role for protons in improving NSCLC outcomes. We close with considerations for next steps and the challenges ahead in using proton therapy for this unique patient population.

Early stage non-small cell lung cancer treated with pencil beam scanning particle therapy: retrospective analysis of early results on safety and efficacy

Background

To evaluate the safety and efficacy of particle therapy (PT) using pencil beam scanning (PBS) technique for early stage non-small cell lung cancer (NSCLC).

Methods

From 08/2014 to 03/2018, 31 consecutive patients with sum of the longest diameters of primary tumor and hilar lymph node < 5 cm, N0–1, M0 NSCLC treated with PT were retrospectively analyzed. Gating/active breathing control techniques were used to control tumor motion in 20 and 7 patients. PBS-based proton radiotherapy (PRT) or carbon ion radiotherapy (CIRT) plans were designed via Syngo® planning system. PRT, PRT + CIRT boost, and CIRT were used in 6, 6 and 19 patients, respectively. Prescriptions were categorized to 3 levels: 5–7.5 GyE * 8–10 Fx, 4–5 GyE * 15–16 Fx and 2.25–3.5 GyE * 20–31 Fx.

Results

Thirty-one patients (20 males and 11 females) with a median age of 71 (50–80) years were enrolled with a median follow-up time of 12.1 (2.9–45.2) months. Fourteen were adenocarcinomas, 7 squamous cell carcinomas, 4 non-specified NSCLC and 6 had no histological diagnosis (4/6 had previous resected lung cancer). The median tumor size was 3.1 (1.1–4.7) cm. No grade 4–5 toxicities were observed. One patient experienced grade 3 (per the Common Terminology Criteria for Adverse Events version 4.03) radiation-induced lung injury (RILI) at 6.7 months from radiation started. Grade 2 acute toxicities included hematological toxicities (5 cases), RILI (2), plural pain (1) and dermatitis (1). Grade 2 late toxicities included RILI (3) and asymptomatic rib fracture (1). Three patients had progressed disease at 4.0~10.6 months after the initiation of PT. One experienced local failure with simultaneous distant failure and died of brain metastasis at 10.8 months; one developed regional and distant failure and died of lung infection at 8.7 months; the other experienced isolated distant failure only and his disease was well controlled after salvage systemic therapy. The estimated rates of progression-free survival, local control, cause-specific survival and overall survival at 1, 2 years were 85.5% and 85.5%, 95.2% and 95.2%, 95.0% and 95.0%, 90.7% and 90.7%, respectively.

Conclusions

PBS-based PT appears safe and effective for early stage NSCLC. Further follow-up and investigation is warranted.

Trial registration

ISRCTN, ISRCTN78973763. Registered 14 August 2018- Retrospectively registered, http://www.isrctn.com/ISRCTN78973763.

Validation of new 2D ripple filters in proton treatments of spherical geometries and non-small cell lung carcinoma cases

A ripple filter (RiFi) is a passive energy modulator used in scanned particle therapy to broaden the Bragg peak, thus lowering the number of accelerator energies required for homogeneous target coverage, which significantly reduces the irradiation time. As we have previously shown, a new 6 mm thick RiFi with 2D groove shapes produced with 3D printing can be used in carbon ion treatments with a similar target coverage and only a marginally worse planning conformity compared to treatments with in-use 3 mm thick RiFis of an older 1D design. Where RiFis are normally not used with protons due to larger scattering and straggling effects, this new design would be beneficial in proton therapy too. Measurements of proton Bragg curves and lateral beam profiles were carried out for different RiFi designs and thicknesses as well as for no RiFi at the Heidelberg Ionenstrahl-Therapiezentrum. Base data for proton treatment planning were generated with the Monte Carlo code SHIELD-HIT12A with and without the 2D 6 mm RiFi. Plans on spherical targets in water were calculated with TRiP98 for a systematic RiFi performance analysis and for comparisons with carbon ion plans for the same respective energy depth step sizes. Plans for 9 stage I static non small cell lung cancer patients were calculated with Eclipse 13.7.15. Dose-volume-histograms, spatial dose distributions and dosimetric indexes were used for plan evaluation. Measurements confirm the functionality of the new 2D RiFi design, which reduces the beam spot size compared to 1D RiFis of the same thickness. Planning studies show that a 6 mm thick 2D RiFi could be used in proton therapy to lower the irradiation time. Although slightly worse planning conformity and dose homogeneity were found for plans with the RiFi compared to plans without, satisfactory results within the planning objective were obtained for all cases.

An effective method to reduce the interplay effects between respiratory motion and a uniform scanning proton beam irradiation for liver tumors: A case study

Purpose

For scanning particle beam therapy, interference between scanning patterns and interfield organ motion may result in suboptimal dose within target volume. In this study, we developed a simple offline correction technique for uniform scanning proton beam (USPB) delivery to compensate for the interplay between scanning patterns and respiratory motion and demonstrate the effectiveness of our technique in treating liver cancer.

Methods

The computed tomography (CT) and respiration data of two patients who had received stereotactic body radiotherapy for hepatocellular carcinoma were used. In the simulation, the relative beam weight delivered to each respiratory phase is calculated for each beam layer after treatment of each fraction. Respiratory phases with beam weights higher than 50% of the largest weight are considered “skipped phases” for the next fraction. For the following fraction, the beam trigger is regulated to prevent beam layers from starting irradiation in skipped phases by extending the interval between each layer. To calculate dose‐volume histogram (DVH), the dose of the target volume at end‐exhale (50% phase) was calculated as the sum of each energy layer, with consideration of displacement due to respiratory motion and relative beam weight delivered per respiratory phase.

Results

For a single fraction, D_1%, D_99%, and V_100% were 114%, 88%, and 32%, respectively, when 8 Gy/min of dose rate was simulated. Although these parameters were improved with multiple fractions, dosimetric inhomogeneity without motion management remained even at 30 fractions, with V_100% 86.9% at 30 fractions. In contrast, the V_100% values with adaptation were 96% and 98% at 20 and 30 fractions, respectively. We developed an offline correction technique for USPB therapy to compensate for the interplay effects between respiratory organ motion and USPB beam delivery.

Conclusions

For liver tumor, this adaptive therapy technique showed significant improvement in dose uniformity even with fewer treatment fractions than normal USPB therapy.

Prognostic impact of underlying lung disease in pulmonary wedge resection for lung cancer

BACKGROUND

Pulmonary wedge resection is an option for lung cancer patients with limited cardiopulmonary preservation. As the impact of underlying lung status on the prognosis of such patients remains unclear, we assessed this issue.

METHODS

A total of 149 borderline surgical candidates with localized lung cancer who had undergone wedge resection were retrospectively investigated. Clinical variables related to perioperative morbidity, local control rate, and oncological outcomes based on underlying lung disease were analyzed.

RESULTS

According to the risk analysis of postoperative complications, underlying lung disease did not influence the surgical morbidity. Postoperative recurrence occurred in 65 patients (locoregional recurrence in 36, distant metastasis in 12, and both simultaneously in 17). Multivariate analysis revealed that emphysema on computed tomography (CT) [hazard ratio (HR) 0.45; 95% confidence interval (CI) 0.21-0.99] was an independent indicator of locoregional recurrence. Forty-four patients died of lung cancer and 29 of other causes. Multivariate analysis demonstrated that interstitial lung disease on CT (HR 1.98; 95% CI 1.01-3.89) was a predictor of poor prognosis.

CONCLUSION

Pulmonary wedge resection can be safely undergone by lung cancer patients regardless of pulmonary comorbidity, although underlying lung disease may influence the prognosis after wedge resection.

4D robust optimization including uncertainties in time structures can reduce the interplay effect in proton pencil beam scanning radiation therapy

PURPOSE

Interplay effects in proton radiotherapy can create large distortions in the dose distribution and severely degrade the plan quality. Standard methods to mitigate these effects include abdominal compression, gating, and rescanning. We propose a new method to include the time structures of the delivery and organ motion in the framework of four-dimensional (4D) robust optimization to generate plans that are robust against interplay effects.

METHODS

The method considers multiple scenarios reflecting the uncertainties in the delivery and in the organ motion. In each scenario, the pencil beam scanning spots are distributed to different phases of the breathing cycle according to each individual spot time stamp, and a partial beam dose is calculated for each phase. The partial beam doses are accumulated on a reference phase through deformable image registrations. Minimax optimization is performed to take all scenarios into account simultaneously. For simplicity, the uncertainties in this proof of concept study are limited to variations in the breathing pattern. The method is evaluated for three different nonsmall cell lung cancer patients and compared to plans using conventional 4D robust optimization both with and without rescanning. We assess the ability of the method to mitigate distortions from the interplay effect over multiple evaluation scenarios using 4D dose calculations. This interplay evaluation is performed in an experimentally validated framework, which is independent of the optimization in the plan generation step.

RESULTS

For the three studied patients, 4D optimization including time structures is efficient, especially for large tumor motions, where rescanning of conventional 4D robustly optimized plans is not sufficient to mitigate the interplay effect. The most efficient approach of the new method is achieved when it is combined with rescanning. For the patient with the largest motion, the mean V95% is 99.2% and mean V107% is 3.65% for the best rescanned 4D plan optimized with time structure. This can be compared to conventional 4D optimized plans with mean V95% of 92.7% and mean V107% of 13.1%.

CONCLUSIONS

The current study shows the potential of reducing interplay effects in proton pencil beam scanning radiotherapy by incorporating organ motion and delivery characteristics in a 4D robust optimization.

Particle therapy in non-small cell lung cancer

The finite range of proton beams in tissues offers unique dosimetric advantages that theoretically allow the dose to the target to be escalated while minimizing exposure of surrounding tissues and thereby minimizing radiation-induced toxicity. These theoretical advantages have led to widespread adoption of proton therapy around the world for a wide variety of tumors at different anatomic sites. Many treatment-planning comparisons have shown that proton therapy has substantial dosimetric advantages over conventional photon (X-ray) radiation therapy. However, given the typically significant difference in cost between proton therapy versus conventional photon therapy, strong evidence of proton therapy's clinical benefits in terms of toxicity and survival is warranted. Some findings from retrospective studies, single-arm prospective studies, and a very few randomized clinical trials comparing these modalities are beginning to emerge. In this review, we examine the available data on proton therapy for (non-small cell lung cancer NSCLC). We begin by discussing the unique challenges involved in treating moving targets with significant tissue heterogeneity and the technologic efforts underway to overcome these challenges. We then discuss the rationale for minimizing normal tissue toxicity, particularly pulmonary, cardiac, and hematologic toxicity, within the context of previously unsuccessful attempts at dose escalation for lung cancer. Finally, we explore strategies for accelerating the development of trials aimed at measuring meaningful clinical endpoints and for maximizing the value of proton therapy by personalizing its use for individual patients.

Image guidance in proton therapy for lung cancer

Proton therapy is a promising but challenging treatment modality for the management of lung cancer. The technical challenges are due to respiratory motion, low dose tolerance of adjacent normal tissue and tissue density heterogeneity. Different imaging modalities are applied at various steps of lung proton therapy to provide information on target definition, target motion, proton range, patient setup and treatment outcome assessment. Imaging data is used to guide treatment design, treatment delivery, and treatment adaptation to ensure the treatment goal is achieved. This review article will summarize and compare various imaging techniques that can be used in every step of lung proton therapy to address these challenges.

Advances in proton therapy in lung cancer

Lung cancer remains the leading cause of cancer deaths in the United States (US) and worldwide. Radiation therapy is a mainstay in the treatment of locally advanced non-small cell lung cancer (NSCLC) and serves as an excellent alternative for early stage patients who are medically inoperable or who decline surgery. Proton therapy has been shown to offer a significant dosimetric advantage in NSCLC patients over photon therapy, with a decrease in dose to vital organs at risk (OARs) including the heart, lungs and esophagus. This in turn, can lead to a decrease in acute and late toxicities in a population already predisposed to lung and cardiac injury. Here, we present a review on proton treatment techniques, studies, clinical outcomes and toxicities associated with treating both early stage and locally advanced NSCLC.

Maximum standardized uptake value on FDG-PET predicts survival in stage I non-small cell lung cancer following carbon ion radiotherapy

The present study (University Hospital Medical Information Network study no. UMIN000003797) aimed to evaluate whether the maximum standardized uptake value (SUV_max) of pretreatment ¹⁸F-fluorodeoxyglucose-positron emission tomography (FDG-PET) is prognostic factor for stage I non-small cell lung cancer (NSCLC) treated with carbon ion radiotherapy (C-ion RT). Patients treated between June 2010 and June 2013 at Gunma University Heavy Ion Medical Center (Maebashi, Japan) on a prospective protocol were included in the present study. Patients with T1a-b and T2a NSCLC were treated with C-ion RT at a dose of 52.8 Gy [relative biological effectiveness (RBE)] and 60.0 Gy (RBE), respectively, in four fractions. Prior to treatment, all patients underwent FDG-PET, in which the SUV_max of primary tumors was evaluated. Local control, progression-free survival (PFS), and overall survival (OS) were calculated. A total of 45 patients were analyzed and the median follow-up period was 28.9 months. The 2-year local control, PFS and OS rates for all patients were 93, 78 and 89%, respectively. The mean SUV_max of primary tumors was 5.5, and patients were divided into higher (≥5.5) and lower (<5.5) SUV_max groups. The 2-year PFS rates were 61 and 89% for the higher and lower SUV_max groups, respectively (P=0.01), and the 2-year OS rates for the higher and lower SUV_max groups were 76 and 96%, respectively (P=0.01). The higher SUV_max group exhibited a significantly worse PFS and OS compared with the lower SUV_max group; however, the SUV_max was not associated with the local control rate. In total, 2 patients (4%) experienced grade 2 or 3 radiation pneumonitis, with their symptoms improved through conservative treatment. No patients experienced any grade 4 or 5 toxicities. The results of the present study indicate that pretreatment SUV_max is a prognostic indicator for outcomes in patients with stage I NSCLC treated with C-ion RT.

Ablative dose proton beam therapy for stage I and recurrent non-small cell lung carcinomas : Ablative dose PBT for NSCLC

PURPOSE

To evaluate the efficacy and safety of ablative dose hypofractionated proton beam therapy (PBT) for patients with stage I and recurrent non-small cell lung carcinoma (NSCLC).

PATIENTS AND METHODS

A total of 55 patients with stage I (n = 42) and recurrent (n = 13) NSCLC underwent hypofractionated PBT and were retrospectively reviewed. A total dose of 50-72 CGE (cobalt gray equivalent) in 5-12 fractions was delivered.

RESULTS

The median follow-up duration was 29 months (range 4-95 months). There were 24 deaths (43.6%) during the follow-up period: 11 died of disease progression and 13 from other causes. Kaplan-Meier overall survival rate (OS) at 3 years was 54.9% and the median OS was 48.6 months (range 4-95 months). Local progression was observed in 7 patients and the median time to local progression was 9.3 months (range 5-14 months). Cumulative actuarial local control rate (LCR), lymph node metastasis-free survival, and distant metastasis-free survival rates at 3 years were 85.4, 78.4, and 76.5%, respectively. Larger tumor diameter was significantly associated with poorer LCR (3-year: 94% for ≤3 cm vs. 65% for >3 cm, p = 0.006) on univariate analysis and also an independent prognostic factor for LCR (HR 6.9, 95% CI = 1.3-37.8, p = 0.026) on multivariate analysis. No grade 3 or 4 treatment-related toxicities developed. One grade 5 treatment-related adverse event occurred in a patient with symptomatic idiopathic pulmonary fibrosis.

CONCLUSIONS

Ablative dose hypofractionated PBT was safe and promising for stage I and recurrent NSCLC.

Treatment Parameters Optimization to Compensate for Interfractional Anatomy Variability and Intrafractional Tumor Motion

Scanned ion beam therapy of lung tumors is severely limited in its clinical applicability by intrafractional organ motion, interference effects between beam and tumor motion (interplay), as well as interfractional anatomic changes. To compensate for dose deterioration caused by intrafractional motion, motion mitigation techniques, such as gating, have been developed. However, optimization of the treatment parameters is needed to further improve target dose coverage and normal tissue sparing. The aim of this study was to determine treatment-planning parameters that permit to recover good target coverage for each fraction of lung tumor treatments. For 9 lung tumor patients from MD Anderson Cancer Center (Houston, Texas), a total of 70 weekly time-resolved computed tomography (4DCT) datasets, which depict the evolution of the patient anatomy over the several fractions of the treatment, were available. Using the GSI in-house treatment planning system TRiP4D, 4D simulations were performed on each weekly 4DCT for each patient using gating and optimization of a single treatment plan based on a planning CT acquired prior to treatment. The impact on target dose coverage (V 95%,CTV) of variations in focus size and length of the gating window, as well as different additional margins and the number of fields was analyzed. It appeared that interfractional variability could potentially have a larger impact on V 95%,CTV than intrafractional motion. However, among the investigated parameters, the use of a large beam spot size, a short gating window, additional margins, and multiple fields permitted to obtain an average V 95%,CTV of 96.5%. In the presented study, it was shown that optimized treatment parameters have an important impact on target dose coverage in the treatment of moving tumors. Indeed, intrafractional motion occurring during the treatment of lung tumors and interfractional variability were best mitigated using a large focus, a short gating window, additional margins, and three fields.

Particle therapy for non-small cell lung tumors: where do we stand? A systematic review of the literature

This review article provides a systematic overview of the currently available evidence on the clinical effectiveness of particle therapy for the treatment of non-small cell lung cancer and summarizes findings of in silico comparative planning studies. Furthermore, technical issues and dosimetric uncertainties with respect to thoracic particle therapy are discussed.

Carbon ion therapy for early-stage non-small-cell lung cancer

Carbon ion therapy is a type of radiotherapies that can deliver high-dose radiation to a tumor while minimizing the dose delivered to the organs at risk; this profile differs from that of photon radiotherapy. Moreover, carbon ions are classified as high-linear energy transfer radiation and are expected to be effective for even photon-resistant tumors. Recently, high-precision radiotherapy modalities such as stereotactic body radiotherapy (SBRT), proton therapy, and carbon ion therapy have been used for patients with early-stage non-small-cell lung cancer, and the results are promising, as, for carbon ion therapy, local control and overall survival rates at 5 years are 80-90% and 40-50%, respectively. Carbon ion therapy may be theoretically superior to SBRT and proton therapy, but the literature that is currently available does not show a statistically significant difference among these treatments. Carbon ion therapy demonstrates a better dose distribution than both SBRT and proton therapy in most cases of early-stage lung cancer. Therefore, carbon ion therapy may be safer for treating patients with adverse conditions such as large tumors, central tumors, and poor pulmonary function. Furthermore, carbon ion therapy may also be suitable for dose escalation and hypofractionation.

Particle beam radiation therapy using carbon ions and protons for oligometastatic lung tumors

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) <110 GyE₁₀, had a significantly higher local recurrence rate. Local control rates were relatively lower in the subsets of patients with the colorectum as the primary tumor site. No local progression was observed in metastases from colorectal cancer irradiated with a BED₁₀ ≥ 110 GyE₁₀. There was no difference in treatment results between proton and carbon ion therapy.

Conclusions

PRBT is well tolerated and effective in the treatment of oligometastatic lung tumors. To further improve local control, high-dose PBRT with a BED₁₀ ≥ 110 GyE₁₀ may be promising. Further investigation of PBRT for lung oligometastases is warranted.

Proton-based stereotactic ablative radiotherapy in early-stage non-small-cell lung cancer

Stereotactic ablative radiotherapy (SABR), a recent implementation in the practice of radiation oncology, has been shown to confer high rates of local control in the treatment of early stage non-small-cell lung cancer (NSCLC). This technique, which involves limited invasive procedures and reduced treatment intervals, offers definitive treatment for patients unable or unwilling to undergo an operation. The use of protons in SABR delivery confers the added physical advantage of normal tissue sparing due to the absence of collateral radiation dose delivered to regions distal to the target. This may translate into clinical benefit and a decreased risk of clinical toxicity in patients with nearby critical structures or limited pulmonary reserve. In this review, we present the rationale for proton-based SABR, principles relating to the delivery and planning of this modality, and a summary of published clinical studies.

Accelerated dose escalation with proton beam therapy for non-small cell lung cancer

Local tumor control remains challenging in many cases of non-small cell lung cancer (NSCLC), particularly those that involve large or centrally located tumors. Concurrent chemotherapy and radiation can maximize tumor control and survival for patients with locally advanced disease, but a substantial proportion of such patients cannot tolerate this therapy, and sequential chemoradiation regimens or radiation given alone at conventionally fractionated doses produces suboptimal results. An alternative approach is the use of hypofractionated proton beam therapy (PBT). The energy distribution of protons can be exploited to reduce involuntary irradiation of normal tissues, particularly the low-dose irradiation problematic in intensity-modulated (photon) radiation therapy (IMRT). Here we summarize current evidence on the use of hypofractionated PBT for both early-stage and locally advanced NSCLC, and the possibility of using hypofractionated regimens for patients who are not candidates for concurrent chemotherapy.

New challenges in high-energy particle radiobiology

Densely ionizing radiation has always been a main topic in radiobiology. In fact, α-particles and neutrons are sources of radiation exposure for the general population and workers in nuclear power plants. More recently, high-energy protons and heavy ions attracted a large interest for two applications: hadrontherapy in oncology and space radiation protection in manned space missions. For many years, studies concentrated on measurements of the relative biological effectiveness (RBE) of the energetic particles for different end points, especially cell killing (for radiotherapy) and carcinogenesis (for late effects). Although more recently, it has been shown that densely ionizing radiation elicits signalling pathways quite distinct from those involved in the cell and tissue response to photons. The response of the microenvironment to charged particles is therefore under scrutiny, and both the damage in the target and non-target tissues are relevant. The role of individual susceptibility in therapy and risk is obviously a major topic in radiation research in general, and for ion radiobiology as well. Particle radiobiology is therefore now entering into a new phase, where beyond RBE, the tissue response is considered. These results may open new applications for both cancer therapy and protection in deep space.

Thoracoscopic lobectomy as salvage surgery for local recurrence of non-small cell lung cancer after carbon ion radiotherapy in an initially operable patient

Carbon ion radiotherapy (CIRT) for patients with early-stage non-small cell lung cancer (NSCLC) has recently provided favorable local control with very few toxic reactions. Because CIRT for NSCLC has been mostly performed for elderly or inoperable patients, salvage surgery for NSCLC after CIRT has rarely been reported. We describe a case of complete thoracoscopic right upper lobectomy with mediastinal lymphadenectomy performed as salvage surgery for local recurrence of stage IA NSCLC after CIRT in an initially operable patient who had refused surgery 27 months previously. Pleural adhesions caused by CIRT were localized to the pulmonary apex and the central pulmonary structures were intact at the time of the salvage surgery, which allowed us to successfully perform thoracoscopic lobectomy without any complications. Thus, salvage surgery for NSCLC after CIRT may be feasible in an initially operable patient, as CIRT appears to be unlikely to cause any difficulties in the salvage surgery.

Clinical outcome of hypofractionated breath-hold image-guided SABR of primary lung tumors and lung metastases

Background

Stereotactic Ablative RadioTherapy (SABR) of lung tumors/metastases has been shown to be an effective treatment modality with low toxicity. Outcome and toxicity were retrospectively evaluated in a unique single-institution cohort treated with intensity-modulated image-guided breath-hold SABR (igSABR) without external immobilization. The dose–response relationship is analyzed based on Biologically Equivalent Dose (BED).

Patients and methods

50 lesions in 43 patients with primary NSCLC (n = 27) or lung-metastases of various primaries (n = 16) were consecutively treated with igSABR with Active-Breathing-Coordinator (ABC®) and repeat-breath-hold cone-beam-CT. After an initial dose-finding/-escalation period, 5x12 Gy for peripheral lesions and single doses of 5 Gy to varying dose levels for central lesions were applied. Overall-survival (OS), progression-free-survival (PFS), progression pattern, local control (LC) and toxicity were analyzed.

Results

The median BED2 was 83 Gy. 12 lesions were treated with a BED2 of <80 Gy, and 38 lesions with a BED2 of >80 Gy. Median follow-up was 15 months. Actuarial 1- and 2-year OS were 67% and 43%; respectively. Cause of death was non-disease-related in 27%. Actuarial 1- and 2-year PFS was 42% and 28%. Progression site was predominantly distant. Actuarial 1- and 2 year LC was 90% and 85%. LC showed a trend for a correlation to BED2 (p = 0.1167). Pneumonitis requiring conservative treatment occurred in 23%.

Conclusion

Intensity-modulated breath-hold igSABR results in high LC-rates and low toxicity in this unfavorable patient cohort with inoperable lung tumors or metastases. A BED2 of <80 Gy was associated with reduced local control.

Particle therapy using carbon ions or protons as a definitive therapy for patients with primary sacral chordoma

OBJECTIVE

This study retrospectively evaluated the efficacy and toxicity of particle therapy using carbon ions or protons for primary sacral chordomas.

METHODS

We evaluated 23 patients with primary sacral chordoma treated with carbon ion therapy (CIT) or proton therapy (PT) between July 2005 and June 2011 at the Hyogo Ion Beam Medical Center, Hyogo, Japan. The median patient age was 72 years. 14 patients were treated with 70.4 Gy equivalents (GyE) in 16 fractions and 9 were treated with 70.4 GyE in 32 fractions. CIT was used for 16 patients, and PT was used for 7 patients.

RESULTS

The median follow-up period was 38 months. At 3 years, local control (LC), overall survival (OS) and progression-free survival (PFS) for all patients were 94%, 83% and 68%, respectively. The log-rank test revealed that male sex was significantly related to better PFS (p=0.029). No other factors, including dose fractionation and ion type, were significant for LC, OS or PFS. In nine patients, ≥ Grade 3 acute dermatitis was observed, and ≥ Grade 3 late toxicities were observed in nine patients. The 32-fraction protocol reduced severe toxicities in both the acute and late phases compared with the 16-fraction protocol.

CONCLUSION

Particle therapy for patients with sacral chordoma showed favourable LC and OS. Severe toxicities were successfully reduced by modifying the dose fractionation and treatment planning in the later treatment era. Thus, this therapeutic modality should be considered useful and safe.

ADVANCES IN KNOWLEDGE

This is the first study including both CIT and PT for sacral chordomas.

Modelling the throughput capacity of a single-accelerator multitreatment room proton therapy centre

OBJECTIVE

We describe a model for evaluating the throughput capacity of a single-accelerator multitreatment room proton therapy centre with the aims of (1) providing quantitative estimates of the throughput and waiting times and (2) providing insight into the sensitivity of the system to various physical parameters.

METHODS

A Monte Carlo approach was used to compute various statistics about the modelled centre, including the throughput capacity, fraction times for different groups of patients and beam waiting times. A method of quantifying the saturation level is also demonstrated.

RESULTS

Benchmarking against the MD Anderson Cancer Center showed good agreement between the modelled (140 ± 4 fractions per day) and reported (133 ± 35 fractions per day) throughputs. A sensitivity analysis of that system studied the impact of beam switch time, the number of treatment rooms, patient set-up times and the potential benefit of having a second accelerator. Finally, scenarios relevant to a potential UK facility were studied, finding that a centre with the same four-room, single-accelerator configuration as the MD Anderson Cancer Center but handling a more complex UK-type caseload would have a throughput reduced by approximately 19%, but still be capable of treating in excess of 100 fractions per 16-h treatment day.

CONCLUSIONS

The model provides a useful tool to aid in understanding the operating dynamics of a proton therapy facility, and for investigating potential scenarios for prospective centres.

ADVANCES IN KNOWLEDGE

The model helps to identify which technical specifications should be targeted for future improvements.

A review of update clinical results of carbon ion radiotherapy

Among various types of ion species, carbon ions are considered to have the most balanced, optimal properties in terms of possessing physically and biologically effective dose localization in the body. This is due to the fact that when compared with photon beams, carbon ion beams offer improved dose distribution, leading to the concentration of the sufficient dose within a target volume while minimizing the dose in the surrounding normal tissues. In addition, carbon ions, being heavier than protons, provide a higher biological effectiveness, which increases with depth, reaching the maximum at the end of the beam's range. This is practically an ideal property from the standpoint of cancer radiotherapy. Clinical studies have been carried out in the world to confirm the efficacy of carbon ions against a variety of tumors as well as to develop effective techniques for delivering an efficient dose to the tumor. Through clinical experiences of carbon ion radiotherapy at the National Institute of Radiological Sciences and Gesellschaft für Schwerionenforschung, a significant reduction in the overall treatment time with acceptable toxicities has been obtained in almost all types of tumors. This means that carbon ion radiotherapy has meanwhile achieved for itself a solid place in general practice. This review describes clinical results of carbon ion radiotherapy together with physical, biological and technological aspects of carbon ions.

Proton Therapy: Ever Shifting Sands and the Opportunities and Obligations within

Proton therapy is associated with significant benefit in terms of normal tissue sparing and potential radiation dose escalation for many patients with malignant diseases. Due to recognition of these qualities, the availability of this technology is increasing rapidly, both through increased availability of large centers, and with the possibility of smaller, lower cost proton therapy centers. Such expansion is associated with increased opportunity to provide this beneficial technology to larger numbers of patients; however, the importance of careful treatment planning and delivery, deliberate patient selection, rigorous scientific investigation including comparison to other technologies when possible, and mindfulness of ethical issues and cost effectiveness must not be forgotten. The obligation to move forward responsibly rests on the shoulders of radiation oncologists around the world. In this article, we discuss current use of proton therapy worldwide, as well as many of the factors that must be taken into account during rapid expansion of this exciting technology.