High-dose proton beam therapy for Stage I non-small-cell lung cancer

Efficacy and Safety in Proton Therapy and Photon Therapy for Patients With Esophageal Cancer: A Meta-Analysis

Importance

Radiotherapy plays an important role in the treatment of esophageal cancer. Proton therapy has unique physical properties and higher relative biological effectiveness. However, whether proton therapy has greater benefit than photon therapy is still unclear.

Objective

To evaluate whether proton was associated with better efficacy and safety outcomes, including dosimetric, prognosis, and toxic effects outcomes, compared with photon therapy and to evaluate the efficacy and safety of proton therapy singly.

Data Sources

A systematic search of PubMed, Embase, the Cochrane Library, Web of Science, SinoMed, and China National Knowledge Infrastructure databases was conducted for articles published through November 25, 2021, and updated to March 25, 2023.

Study Selection

For the comparison of proton and photon therapy, studies including dosimetric, prognosis, and associated toxic effects outcomes were included. The separate evaluation of proton therapy evaluated the same metrics.

Data Extraction and Synthesis

Data on study design, individual characteristics, and outcomes were extracted. If I2 was greater than 50%, the random-effects model was selected. This meta-analysis is reported following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) reporting guideline.

Main Outcomes and Measures

The main outcomes were organs at risk (OARs) dosimetric outcomes, prognosis (overall survival [OS], progression-free survival [PFS], and objective response rate [ORR]), and radiation-related toxic effects.

Results

A total of 45 studies were included in the meta-analysis. For dosimetric analysis, proton therapy was associated with significantly reduced OARs dose. Meta-analysis showed that photon therapy was associated with poor OS (hazard ratio [HR], 1.31; 95% CI, 1.07-1.61; I2 = 11%), but no difference in PFS was observed. Subgroup analysis showed worse OS (HR, 1.42; 95% CI, 1.14-1.78; I2 = 34%) and PFS (HR, 1.48; 95% CI, 1.06-2.08; I2 = 7%) in the radical therapy group with photon therapy. The pathological complete response rate was similar between groups. Proton therapy was associated with significantly decreased grade 2 or higher radiation pneumonitis and pericardial effusion, and grade 4 or higher lymphocytopenia. Single-rate analysis of proton therapy found 89% OS and 65% PFS at 1 year, 71% OS and 56% PFS at 2 years, 63% OS and 48% PFS at 3 years, and 56% OS and 42% PFS at 5 years. The incidence of grade 2 or higher radiation esophagitis was 50%, grade 2 or higher radiation pneumonitis was 2%, grade 2 or higher pleural effusion was 4%, grade 2 or higher pericardial effusion was 3%, grade 3 or higher radiation esophagitis was 8%, and grade 4 or higher lymphocytopenia was 17%.

Conclusions and Relevance

In this meta-analysis, proton therapy was associated with reduced OARs doses and toxic effects and improved prognosis compared with photon therapy for esophageal cancer, but caution is warranted. In the future, these findings should be further validated in randomized clinical trials.

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.

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.

Where are we with proton beam therapy for thoracic malignancies? Current status and future perspectives

Radiation therapy (RT) plays an important role in the curative treatment of a variety of thoracic malignancies. However, delivery of tumoricidal doses with conventional photon-based RT to thoracic tumors often presents unique challenges. Extraneous dose deposited along the entrance and exit paths of the photon beam increases the likelihood of significant acute and delayed toxicities in cardiac, pulmonary, and gastrointestinal structures. Furthermore, safe dose-escalation, delivery of concomitant systemic therapy, or reirradiation of a recurrent disease are frequently not feasible with photon RT. In contrast, protons have distinct physical properties that allow them to deposit a high irradiation dose in the target, while leaving a negligible exit dose in the adjacent organs at risk. Proton beam therapy (PBT), therefore, can reduce toxicities with similar antitumor effect or allow for dose escalation and enhanced antitumor effect with the same or even lower risk of adverse events, thus potentially improving the therapeutic ratio of the treatment. For thoracic malignancies, this favorable dose distribution can translate to decreases in treatment-related morbidities, provide more durable disease control, and potentially prolong survival. This review examines the evolving role of PBT in the treatment of thoracic malignancies and evaluates the data supporting its use.

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.

Differences in failure patterns according to the EGFR mutation status after proton beam therapy for early stage non-small cell lung cancer

We analyzed 135 patients (including 27 EGFR-mutant and 29 EGFR-wild) with T1-3N0M0 non-squamous NSCLC treated by PBT. Considering the 3-year cumulative incidence, the EGFR-mutant group showed a significantly lower infield failure rate (9% vs 27%, p = 0.02) and higher out-of-field failure rate (67% vs 40%, p = 0.02) than the EGFR-wild group.

Proton Beam Therapy for Histologically or Clinically Diagnosed Stage I Non-Small Cell Lung Cancer (NSCLC): The First Nationwide Retrospective Study in Japan

PURPOSE

To investigate the efficacy and safety of proton beam therapy (PBT) for the treatment of stage I non-small cell lung cancer (NSCLC).

METHODS AND MATERIALS

Six hundred sixty-nine patients with 682 tumors histologically or clinically diagnosed stage I NSCLC according to the seventh edition of Union for International Cancer Control who received passive-scattering PBT from April 2004 and December 2013 in Japan were retrospectively reviewed to analyze survival, local control, and toxicities.

RESULTS

Of 669 patients, 486 (72.6%) were men, with a median age of 76 years (range, 42-94 years). NSCLC was histologically confirmed in 440 patients (65.7%). Clinical T stages included T1a (n = 265; 38.9%), T1b (n = 216; 31.7%), and T2a (n = 201; 29.4%). The total irradiation doses of PBT ranged from 74.4 to 131.3 biological effective dose GyE (median, 109.6 biological effective dose GyE). The median follow-up period was 38.2 months (range, 0.6-154.5 months) for all patients. The 3-year overall survival and progression-free survival rates for all patients were 79.5% and 64.1%, respectively. For patients with stage IA tumors, the 3-year overall survival and progression-free survival rates were 82.8% and 70.6%, respectively, and the corresponding rates for patients with stage IB tumors were 70.8% and 47.3%, respectively. The 3-year local progression-free rates for all, stage IA, and stage IB patients were 89.8%, 93.5%, and 79.4%, respectively. The incidence of grade 2, 3, 4, and 5 pneumonitis was 9.8%, 1.0%, 0%, and 0.7%, respectively. The incidence of grade ≥3 dermatitis was 0.4%. No grade 4 or severe adverse events, other than pneumonitis, were observed.

CONCLUSIONS

PBT appears to yield acceptable survival rates, with a low rate of toxicities.

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.

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, D1% , D99% , and V100% 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 V100% 86.9% at 30 fractions. In contrast, the V100% 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.

Stereotactic body radiation therapy (SBRT) for early stage non-small cell lung cancer (NSCLC): contemporary insights and advances

The standard-of-care treatment for early-stage non-small cell lung cancer (NSCLC) continues to be surgery in the form of lobectomy or pneumonectomy. Stereotactic body radiation therapy (SBRT) has evolved as a viable alternative to surgery for medically inoperable patients, achieving excellent local control (LC) with relatively minimal toxicity in standard-risk patients. Nevertheless, the maturation of SBRT has fostered debate regarding its use, technique, dose, and fractionation, particularly in the context of patient- and disease-specific characteristics such as tumor size and location. This review will cover the recent trends and future directions of SBRT as it becomes an increasingly individualized modality in the treatment of early-stage NSCLC.

Clinical results of proton beam therapy for elderly patients with non-small cell lung cancer

BACKGROUND

The purpose of the present study was to evaluate retrospectively the efficacy and safety of proton beam therapy for elderly patients (≥80 years of age) with non-small cell lung cancer.

METHODS

Patients diagnosed with T1-4 N0 M0 non-small cell lung cancer and treated with proton beam therapy between January 2009 and 2015 were recruited from our database retrospectively. Toxicity was evaluated using The Common Terminology Criteria for Adverse Events version 4.0.

RESULTS

Thirty-five patients, including 25 (71%) with clinically inoperable lung cancer, were administered proton beam therapy. The median age was 82 years (range: 80-87 years), and the median follow-up time was 34 months (range: 10-72 months). The median dose of proton beam therapy was 80.0 Gy relative biological effectiveness (RBE) (range: 60.0-80.0 Gy [RBE]), and all patients completed the treatments. All patients were followed for at least 23 months or until their death. The 3-year overall survival rate was 67.2% (90.0% in patients with operable lung cancer, and 58.2% in those with inoperable lung cancer). The 3-year local control rate was 86.5%. Two patients presented with grade 2 pneumonitis. The occurrence rate of grade 2 pneumonitis was significantly correlated with a high lung V20 (p = 0.030), and a high mean lung dose (p = 0.030), and a low ratio of lung volume spared from 0.05 Gy (RBE) dose (total lung volume minus lung volume irradiated at least 0.05 Gy [RBE]) (p = 0.030). However, there were no cases of grade 3 or higher radiation pneumonitis.

CONCLUSIONS

This study suggests that the proton beam therapy was feasible for elderly patients with non-small cell lung cancer and can be considered as one of the treatment choices for elderly patients with lung cancer.

Approaches to stereotactic body radiation therapy for large (≥5 centimeter) non-small cell lung cancer

Although larger (≥5 cm) node-negative non-small cell lung cancer (NSCLC) lesions are altogether uncommon, their incidence may increase following the implementation of lung cancer screening. A rigorous assessment of stereotactic body radiation therapy (SBRT) for these challenging cases is imperative not only owing to concerns of increased risks when delivering ablative doses to large volumes, but also due to lack of prospective data, as these patients were excluded from seminal phase II SBRT trials. In addition to appraising the available institutional or multi-institutional experiences, multiple strategies to reduce toxicities are discussed. These include exploration of several different dose/fractionation schemes and regimens, as well as specialized techniques for SBRT treatment planning and delivery. Because these lesions have a higher rate of occult lymphatic or distant spread, the role of systemic therapies (including chemotherapy and immunotherapy) are also discussed. Altogether, the publication of several key reports, entirely over the last few years, has created a more solid foundation with which to utilize evidence-based management for this unique patient population.

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.

Proton beam therapy in non-small cell lung cancer: state of the art

This review summarizes the past and present status of proton beam therapy (PBT) for lung cancer. PBT has a unique characteristic called the Bragg peak that enables a reduction in the dose of normal tissue around the tumor, but is sensitive to the uncertainties of density changes. The heterogeneity in electron density for thoracic lesions, such as those in the lung and mediastinum, and tumor movement according to respiration necessitates respiratory management for PBT to be applied in lung cancer patients. There are two types of PBT - a passively scattered approach and a scanning approach. Typically, a passively scattered approach is more robust for respiratory movement and a scanning approach could result in a more conformal dose distribution even when the tumor shape is complex. Large tumors of centrally located lung cancer may be more suitably irradiated than with intensity-modulated radiotherapy (IMRT) or stereotactic body radiotherapy (SBRT). For a locally advanced lung cancer, PBT can spare the lung and heart more than photon IMRT. However, no randomized controlled trial has reported differences between PBT and IMRT or SBRT for early-stage and locally advanced lung cancers. Therefore, a well-designed controlled trial is warranted.

High Dose Hypofractionated Proton Beam Therapy is a Safe and Feasible Treatment for Central Lung Cancer

Background

There have been few reports about high total dose hypofractionated proton beam therapy for central lung cancer. The aim of this study was to examine retrospectively the safety and efficacy of high total dose hypofractionated proton beam therapy for central lung cancer.

Patients and methods

Patients treated by proton beam therapy for central lung cancer located less than 2 cm from the trachea, mainstem bronchus, or lobe bronchus were included in this study. All patients received 80 Gy of relative biological dose effectiveness (RBE) in 25 fractions with proton beam therapy over 5 weeks between January 2009 and February 2015. The toxicities were evaluated using the Radiation Therapy Oncology Group and European Organization for Research and Treatment of Cancer criteria.

Results

Twenty patients, including 14 clinically inoperable patients (70%), received proton beam therapy for central lung cancer. The median patient age was 75 years (range: 63–90 years), the median follow up time was 27.5 months (range: 12–72 months), and the median tumor diameter was 39.5 mm (range: 24–81 mm). All patients were followed for at least 20 months or until death. The 2-year overall survival rate was 73.8% (100% in operable patients, and 62.5% in inoperable patients), and the 2-year local control rate was 78.5%. There was no Grade 3 or higher toxicities, including bronchial stricture, obstruction, and fistula.

Conclusions

The present study suggests that a high total dose hypofractionated proton beam therapy for central lung cancer was safe and feasible.

Advances in radiotherapy techniques and delivery for non-small cell lung cancer: benefits of intensity-modulated radiation therapy, proton therapy, and stereotactic body radiation therapy

The 21st century has seen several paradigm shifts in the treatment of non-small cell lung cancer (NSCLC) in early-stage inoperable disease, definitive locally advanced disease, and the postoperative setting. A key driver in improvement of local disease control has been the significant evolution of radiation therapy techniques in the last three decades, allowing for delivery of definitive radiation doses while limiting exposure of normal tissues. For patients with locally-advanced NSCLC, the advent of volumetric imaging techniques has allowed a shift from 2-dimensional approaches to 3-dimensional conformal radiation therapy (3DCRT). The next generation of 3DCRT, intensity-modulated radiation therapy and volumetric-modulated arc therapy (VMAT), have enabled even more conformal radiation delivery. Clinical evidence has shown that this can improve the quality of life for patients undergoing definitive management of lung cancer. In the early-stage setting, conventional fractionation led to poor outcomes. Evaluation of altered dose fractionation with the previously noted technology advances led to advent of stereotactic body radiation therapy (SBRT). This technique has dramatically improved local control and expanded treatment options for inoperable, early-stage patients. The recent development of proton therapy has opened new avenues for improving conformity and the therapeutic ratio. Evolution of newer proton therapy techniques, such as pencil-beam scanning (PBS), could improve tolerability and possibly allow reexamination of dose escalation. These new progresses, along with significant advances in systemic therapies, have improved survival for lung cancer patients across the spectrum of non-metastatic disease. They have also brought to light new challenges and avenues for further research and improvement.

Long-term outcome of phase I/II prospective study of dose-escalated proton therapy for early-stage non-small cell lung cancer

PURPOSE

The aim of this phase I/II study was to assess the long-term clinical benefits and toxicities of proton beam therapy for medically inoperable early-stage non-small cell lung cancer (NSCLC).

PATIENTS AND METHODS

From June 2006 to September 2011, 35 patients with medically inoperable T1N0M0 (central or superior location, 12 patients) or T2-3N0M0 (any location, 23 patients) NSCLC were treated with 87.5Gy at 2.5Gy/fraction of proton therapy. Toxicities were scored according to the Common Terminology Criteria for Adverse Events, version 4.0.

RESULTS

The median follow-up time was 83.1months (95% CI: 69.2-97.1months). For all 35 patients, the 1, 3, and 5-year overall survival rates were 85.7%, 42.9%, and 28.1%, respectively. The 5-year local recurrence-free, regional recurrence-free, and distant metastasis-free survival rates were 85.0%, 89.2%, and 54.4%, respectively. Different T stages had no effect on local and regional recurrence (p=0.499, p=1.00). However, with the increase in T stages, the distant metastasis rate increased significantly (p=0.006). The most common adverse effects were dermatitis (grade 2, 51.4%; grade 3, 2.9%) and radiation pneumonitis (grade 2, 11.4%; grade 3, 2.9%). Other grade 2 toxicities included esophagitis (2.9%), rib fracture (2.9%), heart toxicities (5.7%), and chest wall pain (2.9%).

CONCLUSIONS

According to our long-term follow-up data, proton therapy with ablative doses is well tolerated and effective in medically inoperable early-stage NSCLC. Systemic therapy should be considered to reduce the rate of distant metastasis in cases of T2 and T3 lesions.

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.

Challenges in radiobiological modeling: can we decide between LQ and LQ-L models based on reviewed clinical NSCLC treatment outcome data?

Aim

To study the dose-response of stage I non-small-cell lung cancer (NSCLC) in terms of long-term local tumor control (LC) after conventional and hypofractionated photon radiotherapy, modeled with the linear-quadratic (LQ) and linear-quadratic-linear (LQ-L) approaches and to estimate the clinical α/β ratio within the LQ frame.

Material and methods

We identified studies of curative radiotherapy as single treatment through MedLine search reporting 3-year LC as primary outcome of interest. Logistic models coupled with the biologically effective dose (BED) at isocenter and PTV edge according to both the LQ and LQ-L models with α/β = 10 Gy were fitted. Additionally, α/β was estimated from direct LQ fits.

Results

Thirty one studies were included reporting outcome of 2319 patients. The LQ-L fit yielded a significant value of 11.0 ± 5.2 Gy for the dose threshold (D_t) for BED₁₀ at the isocenter. The LQ and LQ-L fits did not differ substantially. Concerning the estimation of α/β, the value obtained from the direct LQ fit for the complete fractionation range was 3.9 [68 % CI: 2.2–9.0] Gy (p > 0.05).

Conclusion

Both LQ and LQ-L fits can model local tumor control after conventionally and hypofractionated irradiation and are robust methods for predicting clinical effects. The observed dose-effect for local control in NSCLC is weaker at high doses due to data dispersion. For BED₁₀ values of 100–150 Gy in ≥3 fractions, the differences in isoeffects predicted by both models can be neglected.

Electronic supplementary material

The online version of this article (doi:10.1186/s13014-016-0643-5) contains supplementary material, which is available to authorized users.

Consensus Statement on Proton Therapy in Early-Stage and Locally Advanced Non-Small Cell Lung Cancer

Radiation dose escalation has been shown to improve local control and survival in patients with non-small cell lung cancer in some studies, but randomized data have not supported this premise, possibly owing to adverse effects. Because of the physical characteristics of the Bragg peak, proton therapy (PT) delivers minimal exit dose distal to the target volume, resulting in better sparing of normal tissues in comparison to photon-based radiation therapy. This is particularly important for lung cancer given the proximity of the lung, heart, esophagus, major airways, large blood vessels, and spinal cord. However, PT is associated with more uncertainty because of the finite range of the proton beam and motion for thoracic cancers. PT is more costly than traditional photon therapy but may reduce side effects and toxicity-related hospitalization, which has its own associated cost. The cost of PT is decreasing over time because of reduced prices for the building, machine, maintenance, and overhead, as well as newer, shorter treatment programs. PT is improving rapidly as more research is performed particularly with the implementation of 4-dimensional computed tomography-based motion management and intensity modulated PT. Given these controversies, there is much debate in the oncology community about which patients with lung cancer benefit significantly from PT. The Particle Therapy Co-operative Group (PTCOG) Thoracic Subcommittee task group intends to address the issues of PT indications, advantages and limitations, cost-effectiveness, technology improvement, clinical trials, and future research directions. This consensus report can be used to guide clinical practice and indications for PT, insurance approval, and clinical or translational research directions.

The clinical results of proton beam therapy in patients with idiopathic pulmonary fibrosis: a single center experience

Background

The purpose of this study is to retrospectively evaluate the incidence of lung toxicities after proton beam therapy (PBT) in patients with idiopathic pulmonary fibrosis (IPF).

Methods

Patients diagnosed with primary lung cancer or lung metastasis who were treated with PBT between January 2009 and May 2015 were recruited from our database retrospectively. Cases of pneumonitis (excluding infection-related pneumonitis) were evaluated using the Common Terminology Criteria for Adverse Events version 4.0, and the Fletcher-Hugh-Jones classification of respiratory status was used to evaluate pretreatment and posttreatment respiratory function.

Results

Sixteen IPF patients received PBT for lung tumors, 15 received PBT for primary lung cancer, and one patient received PBT for metastasis from lung cancer. The cohort was composed of 14 men and 2 women, with a median age of 76 years (range: 63–89 years). The median follow-up time was 12 months (range: 4–39 months). The median dose of PBT was 80.0 Gy relative biological dose effectiveness (RBE) (range: 66.0–86.4 Gy [RBE]). The cumulative incidence of pneumonitis was 19.8 % (95 % confidence interval [CI]: 0–40.0 %), including one case of grade 5 pneumonitis. Reduced respiratory function was observed after PBT in seven patients, including one patient with pleural dissemination; five of these patients required home oxygen therapy.

Conclusions

This study suggests that PBT can be performed more safely in IPF patients than surgery or X-ray irradiation. Although PBT has become a treatment choice for lung tumors of patients with IPF, the adverse events warrant serious attention.

The Role of Hypofractionated Radiation Therapy with Photons, Protons, and Heavy Ions for Treating Extracranial Lesions

Traditionally, the ability to deliver large doses of ionizing radiation to a tumor has been limited by radiation-induced toxicity to normal surrounding tissues. This was the initial impetus for the development of conventionally fractionated radiation therapy, where large volumes of healthy tissue received radiation and were allowed the time to repair the radiation damage. However, advances in radiation delivery techniques and image guidance have allowed for more ablative doses of radiation to be delivered in a very accurate, conformal, and safe manner with shortened fractionation schemes. Hypofractionated regimens with photons have already transformed how certain tumor types are treated with radiation therapy. Additionally, hypofractionation is able to deliver a complete course of ablative radiation therapy over a shorter period of time compared to conventional fractionation regimens making treatment more convenient to the patient and potentially more cost-effective. Recently, there has been an increased interest in proton therapy because of the potential further improvement in dose distributions achievable due to their unique physical characteristics. Furthermore, with heavier ions the dose conformality is increased and, in addition, there is potentially a higher biological effectiveness compared to protons and photons. Due to the properties mentioned above, charged particle therapy has already become an attractive modality to further investigate the role of hypofractionation in the treatment of various tumors. This review will discuss the rationale and evolution of hypofractionated radiation therapy, the reported clinical success with initially photon and then charged particle modalities, and further potential implementation into treatment regimens going forward.

REAL-TIME LUNG TUMOUR MOTION MODELING FOR ADAPTIVE RADIATION THERAPY USING LEGO MINDSTORMS

An anthropomorphic phantom was built using LEGO Mindstorms® and programmed in LabVIEW® for Adaptive Radiation Therapy (ART) purpose, to simulate the processes of breathing in the lung district during treatments. A thoracic cavity is prototyped by means of an 8 ribs apparatus and 2 artificial tumor masses, driven by intelligent brick LINUX® OS CPU. An optical surface tracking system (VisionRT®) and a QUASAR™ phantom allow correlation between physiological, robotic motion and surrogated signal. Patient's breathing phases are acquired instantaneously by InfraRed/UltraSound sensors. Through 4DCT images, tumor center of mass are individuated and tracked during respiration, to link internal–external organs motion. To quantify the degree of divergences due to dynamics organs deformation, a 4D function was obtained and simulated by our phantom. Sinusoidal signals (6, 10, 12, 15 and 17 Breaths per Minute-BPM) were used for evaluating and commissioning, thereby obtained a correlation coefficient (0.90–0.94) between QUASAR and LEGO. Validated on ideal conditions, phantom was tested in clinical practice. Breaths and CT study of 12 patients were analyzed. Fitting of real breath sinograms returned a mean R value of 0.94 (0.83–0.98) with best model performance achieved in signals with respiratory frequency less than 20 BPM. By using LEGO it is possible to reproduce real patients conditions and simulate normal and even abnormal behavior during the course of therapy, allowing spatial motion estimation.

High-dose proton beam therapy for stage I non-small cell lung cancer: Clinical outcomes and prognostic factors

BACKGROUND

Evidence has suggested that radiation therapy with a lower dose per fraction may be a reasonable option for the treatment of centrally located non-small cell lung cancer (NSCLC). The aim of this study was to evaluate the safety and efficacy of two proton beam therapy (PBT) protocols for stage I NSCLC and to determine prognostic factors.

MATERIAL AND METHODS

This study included patients clinically diagnosed with stage I NSCLC. Based on the location of the tumor, one of the two PBT protocols was administered. Patients with peripherally located tumors were given 66 Gy relative biological dose effectiveness (RBE) over 10 fractions (Protocol A) while patients with centrally located tumors were given 80 Gy (RBE) over 25 fractions (Protocol B).

RESULTS

Between January 2009 and May 2012, 56 eligible patients were enrolled (protocol A: 32 patients; protocol B: 24 patients). The three-year overall survival (OS), progression-free survival (PFS), and local control (LC) rates were 81.3% [95% confidence interval (CI) 75.9-86.7%], 73.4% (95% CI 67.2-79.6%), and 96.0% (95% CI 93.2-98.8%), respectively. There were no significant differences in outcomes between the two protocols. Late grade 2 and 3 pulmonary toxicities were observed in nine patients (13.4%) and one patient (1.5%), respectively; no grade 4 or 5 toxicities were observed. Sex, age, performance status, T-stage, operability, and tumor pathology were not associated with OS and PFS. Only maximum standardized uptake value (SUVmax; <5 vs. ≥5) was identified as a significant prognostic factor for OS and PFS.

CONCLUSION

Both high-dose PBT protocols achieved high LC rates with tolerable toxicities in stage I NSCLC patients, and SUVmax was a significant prognostic factor.

Dosimetric impact of number of treatment fields in uniform scanning proton therapy planning of lung cancer

The main purpose of this study was to perform a treatment planning study for lung cancer comparing 2-field (2F) versus 3-field (3F) techniques in uniform scanning proton therapy (USPT). Ten clinically approved lung cancer treatment plans delivered using USPT at our proton center were included in this retrospective study. All 10 lung cases included 4D computed tomography (CT) simulation. The delineation of target volumes was done based on the maximum intensity projection (MIP) images. Both the 3F and 2F treatment plans were generated for the total dose of 74 cobalt-gray-equivalent (CGE) with a daily dose of 2 CGE. 3F plan was generated by adding an extra beam in the 2F plan. Various dosimetric parameters between 2F and 3F plans were evaluated. 3F plans produced better target coverage and conformality as well as lower mean dose to the lung, with absolute difference between 3F and 2F plans within 2%. In contrast, the addition of third beam led to increase of low-dose regions (V20 and V5) in the lung in 3F plans compared to the ones in 2F plans with absolute difference within 2%. Maximum dose to the spinal cord was lower in 2F plans. Mean dose to the heart and esophagus were comparable in both 3F and 2F plans. In conclusion, the 3F technique in USPT produced better target coverage and conformality, but increased the low-dose regions in the lung when compared to 2F technique.

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.

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.

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.

New radiotherapy approaches in locally advanced non-small cell lung cancer

Radiotherapy plays a major role in the treatment of patients with locally advanced non-small cell lung cancer (NSCLC), particularly since most patients are not suitable for surgery due to the extent of their disease, advanced age and multiple co-morbidities. Despite advances in local and systemic therapies local control and survival remain poor and there is a sense that a therapeutic plateau has been reached with conventional approaches. Strategies for the intensification of radiotherapy such as dose escalation have shown encouraging results in phase I-II trials, but the outcome of the phase III Radiation Therapy Oncology Group 0617 trial was surprisingly disappointing. Hyperfractionated and/or accelerated fractionating schedules have demonstrated superior survival compared to conventional fractionation at the expense of greater oesophageal toxicity. Modern radiotherapy techniques such as the integration of 4-dimensional computed tomography for planning, intensity modulated radiotherapy and image-guided radiotherapy have substantially enhanced the accuracy of the radiotherapy delivery through improved target conformality and incorporation of tumour respiratory motion. A number of studies are evaluating personalised radiation treatment including the concept of isotoxic radiotherapy and the boosting of the primary tumour based on functional imaging. Proton beam therapy is currently under investigation in locally advanced NSCLC. These approaches, either alone or in combination could potentially allow for further dose escalation and improvement of the therapeutic ratio and survival for patients with NSCLC.

Outcomes and prognostic factors for recurrence after high-dose proton beam therapy for centrally and peripherally located stage I non--small-cell lung cancer

INTRODUCTION

This study was conducted to determine disease control rates and prognostic factors associated with recurrence of centrally and peripherally located stage I NSCLC treated using high-dose PBT.

PATIENTS AND METHODS

Seventy-four patients with 80 centrally or peripherally located stage I NSCLCs were treated with PBT. A protocol using 72.6 Gy (RBE) in 22 fractions was used for centrally located tumors, and 66 Gy (RBE) in 10 or 12 fractions was used for peripherally located tumors. Data were collected and control rates and prognostic factors for recurrence were evaluated retrospectively.

RESULTS

The median follow-up period was 31.0 months. The overall survival, disease-specific survival, and progression-free survival rates were 76.7%, 83.0%, and 58.6% at 3 years, respectively. Disease recurrence was noted in 30 patients and local recurrence of 11 tumors occurred. The 3-year local control rate was 86.2% for stage IA tumors and 67.0% for stage IB tumors. Radiation dose was identified as a significant prognostic factor for disease recurrence and local recurrence. Tumor diameter and age were only significantly associated with disease recurrence. The 3-year local control rate was 63.9% for centrally located tumors irradiated with 72.6 Gy (RBE) and 88.4% for peripherally located tumors irradiated with 66 Gy (RBE).

CONCLUSION

Radiation dose was shown to be the most significant prognostic factor for tumor control in stage I NSCLC treated using high-dose PBT. Tumor diameter was not significant for local control. Further evaluation of PBT for centrally located tumors is warranted.

The use of proton-beam therapy in the treatment of non-small-cell lung cancer

Lung cancer is the most common cause of cancer death worldwide. Surgical resection has played a major role in the treatment of non-small-cell lung cancer (NSCLC); however, the disease is often detected in a progressive and inoperable form. Surgical resection may also be impossible for early-stage NSCLC due to medical conditions, such as pulmonary or cardiovascular disease and old age. Radiotherapy plays an important role for these patients. Proton-beam therapy is a particle radiotherapy with an excellent dose localization that permits treatment of lung cancer by administering a high dose to the tumor while minimizing damage to the surrounding normal tissues. Thus, proton beams are increasingly being used for lung cancer. In this context, the authors review the current knowledge on proton-beam therapy for the treatment of NSCLC.

Particle radiotherapy with carbon ion beams

Carbon ion radiotherapy offers superior dose conformity in the treatment of deep-seated malignant tumours compared with conventional X-ray therapy. In addition, carbon ion beams have a higher relative biological effectiveness compared with protons or X-ray beams. The algorithm of treatment planning and beam delivery system is tailored to the individual parameters of the patient. The present article reviews the available literatures for various disease sites including the head and neck, skull base, lung, liver, prostate, bone and soft tissues and pelvic recurrence of rectal cancer as well as physical and biological properties.

Proton therapy radiation pneumonitis local dose-response in esophagus cancer patients

PURPOSE

This study quantifies pulmonary radiation toxicity in patients who received proton therapy for esophagus cancer.

MATERIALS/METHODS

We retrospectively studied 100 esophagus cancer patients treated with proton therapy. The linearity of the enhanced FDG uptake vs. proton dose was evaluated using the Akaike Information Criterion (AIC). Pneumonitis symptoms (RP) were assessed using the Common Toxicity Criteria for Adverse Events version 4.0 (CTCAEv4). The interaction of the imaging response with dosimetric parameters and symptoms was evaluated.

RESULTS

The RP scores were: 0 grade 4/5, 7 grade 3, 20 grade 2, 37 grade 1, and 36 grade 0. Each dosimetric parameter was significantly higher for the symptomatic group. The AIC winning models were 30 linear, 52 linear quadratic, and 18 linear logarithmic. There was no significant difference in the linear coefficient between models. The slope of the FDG vs. proton dose response was 0.022 for the symptomatic and 0.012 for the asymptomatic (p=0.014). Combining dosimetric parameters with the slope did not improve the sensitivity or accuracy in identifying symptomatic cases.

CONCLUSIONS

The proton radiation dose response on FDG PET/CT imaging exhibited a predominantly linear dose response on modeling. Symptomatic patients had a higher dose response slope.

Proton SBRT for medically inoperable stage I NSCLC

INTRODUCTION

The physical properties of proton beam radiation may offer advantages for treating patients with non-small-cell lung cancer (NSCLC). However, its utility for the treatment of medically inoperable stage I NSCLC patients with stereotactic body radiation therapy (SBRT) is unknown.

METHODS

Outcomes for patients with medically inoperable stage I NSCLC treated with proton SBRT were retrospectively analyzed. Proton SBRT was selected as the treatment modality based on pulmonary comorbidities (n = 5), prior chest radiation or/and multiple primary tumors (n = 7), or other reasons (n = 3). Treatments were administered using 2 to 3 proton beams. Treatment toxicity was scored according to common toxicity criteria for adverse events version 4 criteria.

RESULTS

Fifteen consecutive patients and 20 tumors were treated with proton SBRT to 42 to 50 Gy(relative biological effectiveness) in 3 to 5 fractions between July 2008 and September 2010. Treatments were well tolerated with only one case of grade 2 fatigue, one case of grade 2 dermatitis, three cases of rib fracture (maximum grade 2), and one case of grade 3 pneumonitis in a patient with severe chronic obstructive pulmonary disease. With a median follow-up of 24.1 months, 2-year overall survival and local control rates were 64% (95% confidence limits, 34%-83%) and 100% (83%-100%), respectively.

CONCLUSIONS

We conclude that proton SBRT is effective and well tolerated in this unfavorable group of patients. Prospective clinical trials testing the utility of proton SBRT in stage I NSCLC are warranted.

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 for lung cancer

Proton therapy is an emerging radiotherapy technology with the potential to improve the therapeutic index in the treatment of lung cancer patients. Since charged particles, such as protons, have a penetration length that can be modified by using different energies, protons offer the clinician the ability to modulate radiation dose deposition along the beam path. This facilitates an increase of the dose to the tumor target while minimizing the volume of normal tissue irradiation. Such precise delivery is particularly relevant in the setting of lung cancer where the targeted tissues are in close proximity to moderately radiation-sensitive organs like the spinal cord, heart, and esophagus, but are also effectively surrounded by the normal lung, which is extremely sensitive to radiation damage. Proton therapy has been investigated for the treatment of surgically curable yet medically inoperable patients as well as patients with regionally advanced disease.