Carbon ion radiotherapy for stage I non-small cell lung cancer using a regimen of four fractions during 1 week

Carbon Ion Beam Radiation Therapy as Part of a Trimodal Therapy for Non-small Cell Superior Sulcus Tumors: The INKA Study

Purpose

Superior sulcus tumors are frequently treated with neoadjuvant chemoradiation therapy (nCRT) followed by surgery via a trimodal approach. The INKA study evaluated the replacement of photon irradiation by carbon ion radiation therapy (C12-RT) in this regimen.

Methods and Materials

The prospective INKA study included patients with locally advanced non-small cell superior sulcus tumors (

Results

Between 2015 and 2020, 14 patients were included and received nCRT. No grade 3/4 toxicity occurred, with no discontinuation because of toxicity. Before surgery, 8 patients (57%) showed a partial response on computed tomography scan. Thirteen patients showed a metabolic response (metabolic complete remission (mCR), 1; metabolic partial remission (mPR), 12). Three patients (21%) were deemed inoperable after nCRT. In patients with resection, a pathologic Complete remission (CR) was seen in 2 patients (19%) and near-complete remission (<10% vital tumor cells) in 6 patients (55%). Pain score was more than half of that at baseline (mean, 69.2 ± 26.2 vs 30.6 ± 29.1; P = .005) after completion of nCRT and before surgery.

Conclusions

The INKA trial is the first study to evaluate nCRT with C12-RT and showed excellent response, low toxicity, and rapid pain relief.

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Affiliation(s)

Fabian Weykamp Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany National Center for Tumor Diseases (NCT), Heidelberg, Germany Heidelberg Ion-Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
Lukas Schaub Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany National Center for Tumor Diseases (NCT), Heidelberg, Germany
Martin Eichhorn University Hospital Heidelberg, Thoraxklinik, Department of Surgery, Heidelberg, Germany
Hauke Winter University Hospital Heidelberg, Thoraxklinik, Department of Surgery, Heidelberg, Germany
Peter Schirmacher University Hospital Heidelberg, Institute of Pathology, Heidelberg, Germany
Michael Thomas Department of Thoracic Oncology, Thoraxklinik, University of Heidelberg and Translational Lung Research Center Heidelberg (TLRC-H), Member of the German Center for Lung Research (DZL), Heidelberg, Germany
Uwe Haberkorn University Hospital Heidelberg, Department of Nuclear Medicine, Heidelberg, Germany
Malte Ellerbrock Heidelberg Ion-Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany
Sebastian Adeberg Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany National Center for Tumor Diseases (NCT), Heidelberg, Germany Heidelberg Ion-Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany
Jürgen Debus Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany National Center for Tumor Diseases (NCT), Heidelberg, Germany Heidelberg Ion-Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany German Cancer Consortium (DKTK), Partner Site Heidelberg, Germany
Klaus Herfarth Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Heidelberg Institute of Radiation Oncology (HIRO), Heidelberg, Germany National Center for Tumor Diseases (NCT), Heidelberg, Germany Heidelberg Ion-Beam Therapy Center (HIT), Department of Radiation Oncology, Heidelberg University Hospital, Heidelberg, Germany Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), Heidelberg, Germany German Cancer Consortium (DKTK), Partner Site Heidelberg, Germany

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Modeling of the resensitization effect on carbon-ion radiotherapy for stage I non-small cell lung cancer

Objective. To investigate the effect of redistribution and reoxygenation on the 3-year tumor control probability (TCP) of patients with stage I non-small cell lung cancer (NSCLC) treated with carbon-ion radiotherapy.Approach. A meta-analysis of published clinical data of 233 NSCLC patients treated by carbon-ion radiotherapy under 18-, 9-, 4-, and single-fraction schedules was conducted. The linear-quadratic (LQ)-based cell-survival model incorporating the radiobiological 5Rs, radiosensitivity, repopulation, repair, redistribution, and reoxygenation, was developed to reproduce the clinical TCP data. Redistribution and reoxygenation were regarded together as a single phenomenon and termed 'resensitization' in the model. The optimum interval time between fractions was investigated for each fraction schedule using the determined model parameters.Main results.The clinical TCP data for 18-, 9-, and 4-fraction schedules were reasonably reproduced by the model without the resensitization effect, whereas its incorporation was essential to reproduce the TCP data for all fraction schedules including the single fraction. The curative dose for the single-fraction schedule was estimated to be 49.0 Gy (RBE), which corresponds to the clinically adopted dose prescription of 50.0 Gy (RBE). For 18-, 9-, and 4-fraction schedules, a 2-to-3-day interval is required to maximize the resensitization effect during the time interval. In contrast, the single-fraction schedule cannot benefit from the resensitization effect, and the shorter treatment time is preferable to reduce the effect of sub-lethal damage repair during the treatment.Significance.The LQ-based cell-survival model incorporating the radiobiological 5Rs was developed and used to evaluate the effect of the resensitization on clinical results of NSCLC patients treated with hypo-fractionated carbon-ion radiotherapy. The incorporation of the resensitization into the cell-survival model improves the reproducibility to the clinical TCP data. A shorter treatment time is preferable in the single-fraction schedule, while a 2-to-3-day interval between fractions is preferable in the multi-fraction schedules for effective treatments.

Long-Term Outcomes of Ablative Carbon-Ion Radiotherapy for Central Non-Small Cell Lung Cancer: A Single-Center, Retrospective Study

The aim of this study is to assess the efficacy and safety of ablative carbon ion radiotherapy (CIRT) for early stage central non-small cell lung cancer (NSCLC). We retrospectively reviewed 30 patients who had received CIRT at 68.4 Gy in 12 fractions for central NSCLC in 2006-2019. The median age was 75 years, and the median Karnofsky Performance Scale score was 90%. All patients had concomitant chronic obstructive pulmonary disease, and 20 patients (67%) were considered inoperable. In DVH analysis, the median lung V5 and V20 were 15.5% and 10.4%, and the median Dmax, D0.5cc, D2cc of proximal bronchial tree was 65.6 Gy, 52.8 Gy, and 10.0 Gy, respectively. At a median follow-up of 43 months, the 3-year overall survival, disease-specific survival, and local control rates were 72.4, 75.8, and 88.7%, respectively. Two patients experienced grade 3 pneumonitis, but no grade ≥3 adverse events involving the mediastinal organs occurred. Ablative CIRT is feasible and effective for central NSCLC and could be considered as a treatment option, especially for patients who are intolerant of other curative treatments.

Outcomes of carbon ion radiotherapy compared with segmentectomy for ground glass opacity-dominant early-stage lung cancer

PURPOSE

This study aimed to compare the outcomes of patients with ground-grass opacity (GGO)-dominant non-small cell lung cancer (NSCLC) who were treated with carbon ion radiotherapy (CIRT) versus segmentectomy.

METHODS

A retrospective review of medical records was conducted. The study included 123 cases of clinical stage 0/IA peripheral NSCLC treated with single-fraction CIRT from 2003 to 2012, 14 of which were determined to be GGO-dominant and were assigned to CIRT group. As a control, 48 consecutive patients who underwent segmentectomy for peripheral GGO-dominant clinical stage IA NSCLC were assigned to segmentectomy group.

RESULTS

The patients in CIRT group, compared with segmentectomy group, were significantly older (75 ± 7.2 vs. 65 ± 8.2 years, P = 0.000660), more likely to be male (13/14 vs. 22/48, P = 0.00179), and had a lower forced vital capacity (91 ± 19% vs. 110 ± 13%, P = 0.0173). There was a significant difference in the 5-years overall survival rate (86% vs. 96%, P = 0.000860), but not in the 5-years disease-specific survival rate (93% vs. 98%, P = 0.368).

DISCUSSION

Compared with segmentectomy, CIRT may be an alternative option for patients with early GGO-dominant NSCLC who are poor candidates for, or who refuse, surgery.

Creation, evolution, and future challenges of ion beam therapy from a medical physicist's viewpoint (Part 3): Chapter 3. Clinical research, Chapter 4. Future challenges, Chapter 5. Discussion, and Conclusion

Clinical studies of ion beam therapy have been performed at the Lawrence Berkeley Laboratory (LBL), National Institute of Radiological Sciences (NIRS), Gesellschaft für Schwerionenforschung (GSI), and Deutsches Krebsforschungszentrum (DKFZ), in addition to the development of equipment, biophysical models, and treatment planning systems. Although cancers, including brain tumors and pancreatic cancer, have been treated with the Bevalac's neon-ion beam at the LBL (where the first clinical research was conducted), insufficient results were obtained owing to the limited availability of neon-ion beams and immaturity of related technologies. However, the 184-Inch Cyclotron's helium-ion beam yielded promising results for chordomas and chondrosarcomas at the base of the skull. Using carbon-ion beams, NIRS has conducted clinical trials for the treatment of common cancers for which radiotherapy is indicated. Because better results than X-ray therapy results have been obtained for lung, liver, pancreas, and prostate cancers, as well as pelvic recurrences of rectal cancer, the Japanese government recently approved the use of public medical insurance for carbon-ion radiotherapy, except for lung cancer. GSI obtained better results than LBL for bone and soft tissue tumors, owing to dose enhancement enabled by scanning irradiation. In addition, DKFZ compared treatment results of proton and carbon-ion radiotherapy for these tumors. This article summarizes a series of articles (Parts 1-3) and describes future issues of immune ion beam therapy and linear energy transfer optimization.

Comparative Analysis of Photon Stereotactic Radiotherapy and Carbon-Ion Radiotherapy for Elderly Patients with Stage I Non-Small-Cell Lung Cancer: A Multicenter Retrospective Study

The emergence of an aging society and technological advances have made radiotherapy, especially stereotactic body radiotherapy (SBRT), a common alternative to surgery for elderly patients with early stage non-small-cell lung cancer (NSCLC). Carbon-ion radiotherapy (CIRT) is also an attractive treatment option with potentially lower toxicity for elderly patients with comorbidities. We compared the clinical outcomes of the two modalities using Japanese multicenter data. SBRT (n = 420) and single-fraction CIRT (n = 70) data for patients with stage I NSCLC from 20 centers were retrospectively analyzed. Contiguous patients ≥ 80 years of age were enrolled, and overall survival (OS), disease-specific survival (DSS), local control (LC), and adverse event rates were compared. The median age was 83 years in both groups and the median follow-up periods were 28.5 and 42.7 months for SBRT and CIRT, respectively. The 3-year OS, DSS, and LC rates were 76.0% vs. 72.3% (p = 0.21), 87.5% vs. 81.6% (p = 0.46), and 79.2% vs. 78.2% (p = 0.87), respectively, for the SBRT vs. CIRT groups. Regarding toxicity, 2.9% of the SBRT group developed grade ≥ 3 radiation pneumonitis, whereas none of the CIRT group developed grade ≥ 2 radiation pneumonitis. SBRT and CIRT in elderly patients showed similar survival and LC rates, although CIRT was associated with less severe radiation pneumonitis.

Real-time deep neural network-based automatic bowel gas segmentation on X-ray images for particle beam treatment

Since particle beam distribution is vulnerable to change in bowel gas because of its low density, we developed a deep neural network (DNN) for bowel gas segmentation on X-ray images. We used 6688 image datasets from 209 cases as training data, 736 image datasets from 23 cases as validation data and 102 image datasets from 51 cases as test data (total 283 cases). For the training data, we prepared three types of digitally reconstructed radiographic (DRR) images (all-density, bone and gas) by projecting the treatment planning CT image data. However, the real X-ray images acquired in the treatment room showed low contrast that interfered with manual delineation of bowel gas. Therefore, we used synthetic X-ray images converted from DRR images in addition to real X-ray images.We evaluated DNN segmentation accuracy for the synthetic X-ray images using Intersection over Union, recall, precision, and the Dice coefficient, which measured 0.708 ± 0.208, 0.832 ± 0.170, 0.799 ± 0.191, and 0.807 ± 0.178, respectively. The evaluation metrics for the real X-images were less accurate than those for the synthetic X-ray images (0.408 ± 0237, 0.685 ± 0.326, 0.490 ± 0272, and 0.534 ± 0.271, respectively). Computation time was 29.7 ± 1.3 ms/image. Our DNN appears useful in increasing treatment accuracy in particle beam therapy.

Comparison of dosimetries of carbon-ion pencil beam scanning, proton pencil beam scanning and volumetric modulated arc therapy for locally recurrent rectal cancer

We compared the dose distributions of carbon-ion pencil beam scanning (C-PBS), proton pencil beam scanning (P-PBS) and Volumetric Modulated Arc Therapy (VMAT) for locally recurrent rectal cancer. The C-PBS treatment planning computed tomography (CT) data sets of 10 locally recurrent rectal cancer cases were randomly selected. Three treatment plans were created using identical prescribed doses. The beam angles for C-PBS and P-PBS were identical. Dosimetry, including the dose received by 95% of the planning target volume (PTV) (D95%), dose to the 2 cc receiving the maximum dose (D2cc), organ at risk (OAR) volume receiving > 15Gy (V15) and > 30Gy (V30), was evaluated. Statistical significance was assessed using the Wilcoxon signed-rank test. Mean PTV-D95% values were > 95% of the volume for P-PBS and C-PBS, whereas that for VMAT was 94.3%. However, PTV-D95% values in P-PBS and VMAT were < 95% in five and two cases, respectively, due to the OAR dose reduction. V30 and V15 to the rectum/intestine for C-PBS (V30 = 4.2 ± 3.2 cc, V15 = 13.8 ± 10.6 cc) and P-PBS (V30 = 7.3 ± 5.6 cc, V15 = 21.3 ± 13.5 cc) were significantly lower than those for VMAT (V30 = 17.1 ± 10.6 cc, V15 = 55.2 ± 28.6 cc). Bladder-V30 values with P-PBS/C-PBS (3.9 ± 4.8 Gy(RBE)/3.0 ± 4.0 Gy(RBE)) were significantly lower than those with VMAT (7.9 ± 8.1 Gy). C-PBS provided superior dose conformation and lower OAR doses compared with P-PBS and VMAT. C-PBS may be the best choice for cases in which VMAT and P-PBS cannot satisfy dose constraints. C-PBS could be another choice for cases in which VMAT and P-PBS cannot satisfy dose constraints, thereby avoiding surgical resection.

Research Progress of Heavy Ion Radiotherapy for Non-Small-Cell Lung Cancer

Non-small-cell lung cancer (NSCLC) has a high incidence and poses a serious threat to human health. However, the treatment outcomes of concurrent chemoradiotherapy for non-small-cell lung cancer are still unsatisfactory, especially for high grade lesions. As a new cancer treatment, heavy ion radiotherapy has shown promising efficacy and safety in the treatment of non-small-cell lung cancer. This article discusses the clinical progress of heavy ion radiotherapy in the treatment of non-small-cell lung cancer mainly from the different cancer stages, the different doses of heavy ion beams, and the patient's individual factors, and explores the deficiency of heavy ion radiotherapy in the treatment of non-small-cell lung cancer and the directions of future research, in order to provide reference for the wider and better application of heavy ion radiotherapy in the future.

A Promising Treatment Strategy for Lung Cancer: A Combination of Radiotherapy and Immunotherapy

Lung cancer is a leading cause of cancer-related deaths worldwide despite advances in treatment. In the past few decades, radiotherapy has achieved outstanding technical advances and is being widely used as a definitive, prophylactic, or palliative treatment of patients with lung cancer. The anti-tumor effects of radiotherapy are considered to result in DNA damage in cancer cells. Moreover, recent evidence has demonstrated another advantage of radiotherapy: the induction of anti-tumor immune responses, which play an essential role in cancer control. In contrast, radiotherapy induces an immunosuppressive response. These conflicting reactions after radiotherapy suggest that maximizing immune response to radiotherapy by combining immunotherapy has potential to achieve more effective anti-tumor response than using each alone. Immune checkpoint molecules, such as cytotoxic T-lymphocyte-associated protein 4, programmed cell death-1/programmed death-ligand 1, and their inhibitors, have attracted significant attention for overcoming the immunosuppressive conditions in patients with cancer. Therefore, the combination of immune checkpoint inhibitors and radiotherapy is promising. Emerging preclinical and clinical studies have demonstrated the rationale for these combination strategies. In this review, we outlined evidence suggesting that combination of radiotherapy, including particle therapy using protons and carbon ions, with immunotherapy in lung cancer treatment could be a promising treatment strategy.

Virtual randomized study comparing lobectomy and particle beam therapy for clinical stage IA non-small cell lung cancer in operable patients

To the best of our knowledge there have been no randomized controlled trials comparing lobectomy-a standard treatment for patients with early-stage non-small cell lung cancer (NSCLC)-and particle beam therapy (PBT), the best performing existing radiotherapy. We conducted a virtual randomized trial in medically operable patients with stage IA NSCLC to compare lobectomy and PBT effectiveness. A Markov model was developed to predict life expectancy after lobectomy and PBT in a cohort of patients with stage IA NSCLC. Ten thousand virtual patients were randomly assigned to each group. Sensitivity analyses were performed as model variables and scenarios changed to determine which treatment strategy was best for improving life expectancy. All estimated model parameters were determined using variables extracted from a systematic literature review of previously published articles. The preferred strategy differed depending on patient age. In young patients, lobectomy showed better life expectancy than that of PBT. The difference in life expectancy between lobectomy and PBT was statistically insignificant in older patients. Our model predicted lobectomy as the preferred strategy when operative mortality was under 5%. However, the preferred strategy changed to PBT if operative mortality post lobectomy was over 5%. For medically operable patients with stage IA NSCLC, our Markov model revealed the preferred strategy of lobectomy or PBT regarding operative mortality changed with varying age and comorbidity. Until randomized controlled trial results become available, we hope the current results will provide a rationale background for clinicians to decide treatment modalities for patients with stage IA NSCLC.

Efficacy and Safety of Carbon-Ion Radiotherapy for Stage I Non-Small Cell Lung Cancer with Coexisting Interstitial Lung Disease

Simple Summary

Interstitial lung disease (ILD) is a risk factor for lung cancer, but the treatment options are often limited because of concerns that ILD may worsen with treatment. In this study, we analyzed whether the presence or absence of ILD affects the outcome of carbon-ion radiotherapy (CIRT) for clinical stage I non-small cell lung cancer (NSCLC). For all cases, CT and clinical data were reviewed by a respiratory physician to determine the presence of ILD. Overall survival and disease-specific survival were lower in patients with ILD than in patients without ILD. There was no significant difference between the ILD group and the non-ILD group with respect to safety. CIRT was not associated with significantly more side-effects in patients with ILD than in patients without ILD. Coexisting ILD was a poor prognostic factor with respect to CIRT for clinical stage I lung cancer, as reported for other treatment methods.

Abstract

Interstitial lung disease (ILD) is a risk factor both for the development and treatment failure of lung cancer. In this retrospective study, we analyzed the outcome of carbon-ion radiotherapy (CIRT) in 124 patients with clinical stage I non-small cell lung cancer (NSCLC), of whom 26 (21%) had radiological signs of pre-existing ILD. ILD was diagnosed retrospectively by a pulmonologist based on critical review of CT-scans. Ninety-eight patients were assigned to the non-ILD group and 26 patients (21.0%) to the ILD group. There were significant differences in pre-treatment KL-6 values between the two groups. The three year overall survival and cause-specific survival rates were 83.2% and 90.7%, respectively, in the non-ILD group, and 59.7% and 59.7%, respectively, in the ILD group (between-group differences, p = 0.002 and p < 0.001). Radiation pneumonitis worse than Grade 2 was observed in three patients (3.0%) in the non-ILD group and two patients (7.6%) in the ILD group (p = 0.29). There were no cases of acute exacerbation in the ILD group. CIRT for stage I NSCLC was as safe in the ILD group as in the non-ILD group. Coexisting ILD was a poor prognostic factor in CIRT for clinical stage I lung cancer.

Who Will Benefit from Charged-Particle Therapy?

Charged-particle therapy (CPT) such as proton beam therapy (PBT) and carbon-ion radiotherapy (CIRT) exhibit substantial physical and biological advantages compared to conventional photon radiotherapy. As it can reduce the amount of radiation irradiated in the normal organ, CPT has been mainly applied to pediatric cancer and radioresistent tumors in the eloquent area. Although there is a possibility of greater benefits, high set-up cost and dearth of high level of clinical evidence hinder wide applications of CPT. This review aims to present recent clinical results of PBT and CIRT in selected diseases focusing on possible indications of CPT. We also discussed how clinical studies are conducted to increase the number of patients who can benefit from CPT despite its high cost.

The Risk Factors for Radiation Pneumonitis After Single-Fraction Carbon-Ion Radiotherapy for Lung Cancer or Metastasis

There are no studies on the risk factors of radiation pneumonitis (RP) after carbon-ion radiotherapy at a dose of 50 Gy (relative biological effectiveness (RBE)) in a single fraction. The objective of this study was to identify factors associated with RP after radiotherapy, including dose-volume parameters. Ninety-eight patients without a history of thoracic radiotherapy who underwent treatment for solitary lung tumors between July 2013 and April 2016 were retrospectively analyzed. Treatment was planned using Xio-N. The median follow-up duration was 53 months, and the median clinical target volume was 32.3 mL. Three patients developed grade 2 RP, and one patient developed grade 3 interstitial pneumonitis. None of the patients developed grade 4 or 5 RP. The dose-volume parameters of the normal lung irradiated at least with 5-30 Gy (RBE), and the mean lung dose was significantly lower in patients with grade 0-1 RP than in those with grade 2-3 RP. Pretreatment with higher SP-D and interstitial pneumonitis were significant factors for the occurrence of symptomatic RP. The present study showed a certain standard for single-fraction carbon-ion radiotherapy that does not increase the risk of RP; however, further validation studies are needed.

High-dose hypofractionated pencil beam scanning carbon ion radiotherapy for lung tumors: Dosimetric impact of different spot sizes and robustness to interfractional uncertainties

PURPOSE

The robustness against setup and motion uncertainties of gated four-dimensional restricted robust optimization (4DRRO) was investigated for hypofractionated carbon ion radiotherapy (CIRT) of lung tumors.

METHODS

CIRT plans of 9 patients were optimized using 4DRRO strategy with 3 mm setup errors, 3% density errors and 3 breathing phases related to the gate window. The prescription was 60 Gy(RBE) in 4 fractions. Standard spots (SS) were compared to big spots (BS). Plans were recalculated on multiple 4DCTs acquired within 3 weeks from treatment simulation and rigidly registered with planning images using bone matching. Warped dose distributions were generated using deformable image registration and accumulated on the planning 4DCTs. Target coverage (D98%, D95% and V95%) and dose to lung were evaluated in the recalculated and accumulated dose distributions.

RESULTS

Comparable target coverage was obtained with both spot sizes (p = 0.53 for D95%). The mean lung dose increased of 0.6 Gy(RBE) with BS (p = 0.0078), still respecting the dose constraint of a 4-fraction stereotactic treatment for the risk of radiation pneumonitis. Statistically significant differences were found in the recalculated and accumulated D95% (p = 0.048 and p = 0.024), with BS showing to be more robust. Using BS, the average degradations of the D98%, D95% and V95% in the accumulated doses were -2.7%, -1.6% and -1.5%.

CONCLUSIONS

Gated 4DRRO was highly robust against setup and motion uncertainties. BS increased the dose to healthy tissues but were more robust than SS. The selected optimization settings guaranteed adequate target coverage during the simulated treatment course with acceptable risk of toxicity.

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.

Physics of Particle Beam and Hypofractionated Beam Delivery in NSCLC

The dosimetric advantages of particle therapy lead to significantly reduced integral dose to normal tissues, making it an attractive treatment option for body sites such as the thorax. With reduced normal tissue dose comes the potential for dose escalation, toxicity reduction, or hypofractionation. While proton and heavy ion therapy have been used extensively for NSCLC, there are challenges in planning and delivery compared with X-ray-based radiation therapy. Particularly, range uncertainties compounded by breathing motion have to be considered. This article summarizes the current state of particle therapy for NSCLC with a specific focus on the impact of dosimetric uncertainties in planning and delivery.

Effectiveness of fractionated carbon ion treatments in three rat prostate tumors differing in growth rate, differentiation and hypoxia

PURPOSE

To quantify the fractionation dependence of carbon (¹²C) ions and photons in three rat prostate carcinomas differing in growth rate, differentiation and hypoxia.

MATERIAL AND METHODS

Three sublines (AT1, HI, H) of syngeneic rat prostate tumors (R3327) were treated with six fractions of either ¹²C-ions or 6 MV photons. Dose-response curves were determined for the endpoint local tumor control within 300 days. The doses at 50% control probability (TCD₅₀) and the relative biological effectiveness (RBE) of ¹²C-ions were calculated and compared with the values from single and split dose studies.

RESULTS

Experimental findings for the three tumor sublines revealed (i) a comparably increased RBE (2.47-2.67), (ii) a much smaller variation of the radiation response for ¹²C-ions (TCD₅₀: 35.8-43.7 Gy) than for photons (TCD₅₀: 91.3-116.6 Gy), (iii) similarly steep (AT1) or steeper (HI, H) dose-response curves for ¹²C-ions than for photons, (iv) a larger fractionation effect for photons than for ¹²C-ions, and (v) a steeper increase of the RBE with decreasing fractional dose for the well-differentiated H- than for the less-differentiated HI- and AT1-tumors, reflected by (vi) the smallest α/β-value for H-tumors after photon irradiation.

CONCLUSION

¹²C-ions reduce the radiation response heterogeneity between the three tumor sublines as well as within each subline relative to photon treatments, independently of fractionation. The dose dependence of the RBE varies between tumors of different histology. The results support the use of hypofractionated carbon ion treatments in radioresistant tumors.

Comparison of Oncologic Outcomes between Carbon Ion Radiotherapy and Stereotactic Body Radiotherapy for Early-Stage Non-Small Cell Lung Cancer

Simple Summary

Lung cancer is a leading cause of cancer-related death. Stereotactic body radiotherapy (SBRT) is the standard treatment for inoperable early-stage non-small cell lung cancer (NSCLC). Carbon ion radiotherapy (CIRT) is a safe and effective treatment for early-stage NSCLC. However, there is no direct comparison study between these treatments. The present study aimed to compare oncologic outcomes after CIRT and SBRT for early-stage NSCLC in a single-institutional and contemporaneous cohort. We demonstrated favorable overall survival and local control in the CIRT group compared to those in the SBRT group using log-rank tests and Cox regression analyses for 89 patients. In addition, these results were validated in propensity score-adjusted analyses. The present retrospective comparison study showed a positive efficacy profile of CIRT, which is beneficial in the management of early-stage NSCLC.

Abstract

Lung cancer is a leading cause of cancer-related deaths worldwide. Radiotherapy is an essential treatment modality for inoperable non-small cell lung cancer (NSCLC). Stereotactic body radiotherapy (SBRT) is the standard treatment for early-stage NSCLC because of its favorable local control (LC) compared to conventional radiotherapy. Carbon ion radiotherapy (CIRT) is a kind of external beam radiotherapy characterized by a steeper dose distribution and higher biological effectiveness. Several prospective studies have shown favorable outcomes. However, there is no direct comparison study between CIRT and SBRT to determine their benefits in the management of early-stage NSCLC. Thus, we conducted a retrospective, single-institutional, and contemporaneous comparison study, including propensity score-adjusted analyses, to clarify the differences in oncologic outcomes. The 3-year overall survival (OS) was 80.1% in CIRT and 71.6% in SBRT (p = 0.0077). The 3-year LC was 87.7% in the CIRT group and 79.1% in the SBRT group (p = 0.037). Multivariable analyses showed favorable OS and LC in the CIRT group (hazard risk [HR] = 0.41, p = 0.047; HR = 0.30, p = 0.040, respectively). Log-rank tests after propensity score matching and Cox regression analyses using propensity score confirmed these results. These data provided a positive efficacy profile of CIRT for early-stage NSCLC.

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.

Estimating the Number of Patients Eligible for Carbon Ion Radiotherapy in the United States

Purpose

Carbon ion radiotherapy (CIRT) is an emerging radiotherapy modality with potential advantages over conventional photon-based therapy, including exhibiting a Bragg peak and greater relative biological effectiveness, leading to a higher degree of cell kill. Currently, 13 centers are treating with CIRT, although there are no centers in the United States. We aimed to estimate the number of patients eligible for a CIRT center in the United States.

Materials and Methods

Using the National Cancer Database, we analyzed the incidence of cancers frequently treated with CIRT internationally (glioblastoma, hepatocellular carcinoma, cholangiocarcinoma, locally advanced pancreatic cancer, non-small cell lung cancer, localized prostate cancer, soft tissue sarcomas, and specific head and neck cancers) diagnosed in the United States in 2015. The percentage and number of patients likely benefiting from CIRT was estimated with inclusion criteria from clinical trials and retrospective studies, and that ratio was applied to 2019 cancer statistics. An adaption correction rate was applied to estimate the potential number of patients treated with CIRT. Given the high dependency on prostate and lung cancers and the uncertain adoption of CIRT in those diseases, the data were then reanalyzed excluding those diagnoses.

Results

Of the 1 127 455 new cases of cancer diagnosed in the United States in 2015, there were 213 073 patients (18.9%) eligible for treatment with CIRT based on inclusion criteria. When applying this rate and the adaption correction rate to the 2019 incidence data, an estimated 89 946 patients (42.2% of those fitting inclusion criteria) are eligible for CIRT. Excluding prostate and lung cancers, there were an estimated 8922 patients (10% of those eligible for CIRT) eligible for CIRT. The number of patients eligible for CIRT is estimated to increase by 25% to 27.7% by 2025.

Conclusion

Our analysis suggests a need for CIRT in the United States in 2019, with the number of patients possibly eligible to receive CIRT expected to increase during the coming 5 to 10 years.

A clinical study of curative partial breast irradiation for stage I breast cancer using carbon ion radiotherapy

Background and purpose

Our institute initiated carbon ion radiotherapy research for patients with stage I breast cancer in April 2013. The purpose of this article is to evaluate the treatment outcome of cases treated outside clinical trial up to May 2020.

Materials and methods

Eligibility criteria of the patients were having untreated stage I breast cancer and being unsuitable for operation for physical or mental reasons. The irradiated volume was defined as the gross tumor including intraductal components. The dose escalation study was initially conducted four times a week for a total of 52.8 Gy [relative biological efficacy (RBE)]. After confirming that adverse effects were within acceptable range, the total dose was increased to 60.0 Gy (RBE).

Results

Between April 2013 and November 2015, 14 cases were treated. The median follow up period was 61 months. No adverse toxicities were observed except for grade 1 acute skin reaction in 10 cases. The time required from carbonion radiotherapy to tumor disappearance was 3 months in 1 case, 6 months in 3 cases, 12 months in 4 cases, and 24 months in 5 cases. The third case developed local recurrence 6 months after radiotherapy. Twelve patients with luminal subtype received 5-year endocrine therapy. Thirteen of 14 tumors have been maintaining complete response with excellent cosmetic results.

Conclusions

The time from carbon ion radiotherapy to tumor disappearance was longer than expected, but complete tumor disappearance was observed except for one high-grade case. With careful patient selection, carbonion radiotherapy in patients with stage I breast cancer is deemed effective and safe, and further research is recommended.

Image-Guided Hypofractionated Proton Therapy in Early-Stage Non-Small Cell Lung Cancer: A Phase 2 Study

Purpose

Due to the excellent outcomes with image-guided stereotactic body radiotherapy for patients with early-stage non–small cell lung cancer (NSCLC) and the low treatment-related toxicities using proton therapy (PT), we investigated treatment outcomes and toxicities when delivering hypofractionated PT.

Materials and Methods

Between 2009 and 2018, 22 patients with T1 to T2 N0M0 NSCLC (45% T1, 55% T2) received image-guided hypofractionated PT. The median age at diagnosis was 72 years (range, 58-90). Patients underwent 4-dimensional computed tomography simulation following fiducial marker placement, and daily image guidance was performed. Nine patients (41%) were treated with 48 GyRBE in 4 fractions for peripheral lesions, and 13 patients (59%) were treated with 60 GyRBE in 10 fractions for central lesions. Patients were assessed for CTCAEv4 toxicities with computed tomography imaging for tumor assessment. The primary endpoint was grade 3 to 5 toxicity at 1 year.

Results

The median follow-up for all patients was 3.5 years (range, 0.2-8.8 years). The overall survival rates at 3 and 5 years were 81% and 49%, respectively. Cause-specific survival rates at 3 and 5 years were 100% and 75%, respectively. The 3-year local, regional, and distant control rates were 86%, 85%, and 95%, respectively. Four patients experienced in-field recurrences between 18 and 45 months after treatment. One patient (5%) developed a late grade 3 bronchial stricture requiring hospitalization and stent.

Conclusion

Image-guided hypofractionated PT for early-stage NSCLC provides promising local control and long-term survival with a low likelihood of toxicity. Regional nodal and distant relapses remain a problem.

Radiosensitization of NSCLC cells to X-rays and carbon ions by the CHK1/CHK2 inhibitor AZD7762, Honokiol and Tunicamycin

Although radiotherapy, especially carbon-ion radiotherapy, is an effective treatment modality against non-small-cell lung cancer (NSCLC), studies using radiation combined with sensitizer for improving the efficacy of radiotherapy are still needed. In this work, we aimed to investigate in NSCLC A549 and H1299 cell lines the effects of different linear energy transfer (LET) radiations combined with diverse sensitizing compounds. Cells pretreated with the CHK1/CHK2 inhibitor AZD7762, Honokiol or Tunicamycin were irradiated with low-LET X-rays and high-LET carbon ions. Cell survival was assessed using the clonogenic cell survival assay. Cell cycle distribution and apoptosis were measured with flow cytometry, and DNA double strand break (DSB) and repair were detected using γ-H2AX immunofluorescence staining. Our results revealed that AZD7762, Honokiol and Tunicamycin demonstrated low cytotoxicity to NSCLC cells and a pronounced radiosensitizing effect on NSCLC cells exposed to carbon ions than X-rays. Unrepaired DNA DSB damages, the abrogation of G2/M arrest induced by irradiation, and finally apoptotic cell death were the main causes of the radiosensitizing effect. Thus, our data suggest that high-LET carbon ion combined with these compounds may be a potentially effective therapeutic strategy for locally advanced NSCLC.

The relative biological effectiveness of carbon ion radiation therapy for early stage lung cancer

BACKGROUND AND PURPOSE

Carbon ion radiation therapy (CIRT) is recognized as an effective alternative treatment modality for early stage lung cancer, but a quantitative understanding of relative biological effectiveness (RBE) compared to photon therapy is lacking. In this work, a mechanistic tumor response model previously validated for lung photon radiotherapy was used to estimate the RBE of CIRT compared to photon radiotherapy, as a function of dose and the fractionation schedule.

MATERIALS AND METHODS

Clinical outcome data of 9 patient cohorts (394 patients) treated with CIRT for early stage lung cancer, representing all published data, were included. Fractional dose, number of fractions, treatment schedule, and local control rates were used for model simulations relative to standard photon outcomes. Four parameters were fitted: α, α/β, and the oxygen enhancement ratios of cells either accessing only glucose, not oxygen (OER_I), or cells dying from starvation (OER_H). The resulting dose-response relationship of CIRT was compared with the previously determined dose-response relationship of photon radiotherapy for lung cancer, and an RBE of CIRT was derived.

RESULTS

Best-fit CIRT parameters were: α = 1.12 Gy^-1 [95%-CI: 0.97-1.26], α/β = 23.9 Gy [95%-CI: 8.9-38.9], and the oxygen induced radioresistance of hypoxic cell populations were characterized by OER_I = 1.08 [95%-CI: 1.00-1.41] (cells lacking oxygen but not glucose), and OER_H = 1.01 [95%-CI: 1.00-1.44] (cells lacking oxygen and glucose). Depending on dose and fractionation, the derived RBE ranges from 2.1 to 1.5, with decreasing values for larger fractional dose and fewer number of fractions.

CONCLUSION

Fitted radiobiological parameters were consistent with known carbon in vitro radiobiology, and the resulting dose-response curve well-fitted the reported data over a wide range of dose-fractionation schemes. The same model, with only a few fitted parameters of clear mechanistic meaning, thus synthesizes both photon radiotherapy and CIRT clinical experience with early stage lung tumors.

CSC Radioresistance: A Therapeutic Challenge to Improve Radiotherapy Effectiveness in Cancer

Radiotherapy (RT) is a modality of oncologic treatment that can be used to treat approximately 50% of all cancer patients either alone or in combination with other treatment modalities such as surgery, chemotherapy, immunotherapy, and therapeutic targeting. Despite the technological advances in RT, which allow a more precise delivery of radiation while progressively minimizing the impact on normal tissues, issues like radioresistance and tumor recurrence remain important challenges. Tumor heterogeneity is responsible for the variation in the radiation response of the different tumor subpopulations. A main factor related to radioresistance is the presence of cancer stem cells (CSC) inside tumors, which are responsible for metastases, relapses, RT failure, and a poor prognosis in cancer patients. The plasticity of CSCs, a process highly dependent on the epithelial–mesenchymal transition (EMT) and associated to cell dedifferentiation, complicates the identification and eradication of CSCs and it might be involved in disease relapse and progression after irradiation. The tumor microenvironment and the interactions of CSCs with their niches also play an important role in the response to RT. This review provides a deep insight into the characteristics and radioresistance mechanisms of CSCs and into the role of CSCs and tumor microenvironment in both the primary tumor and metastasis in response to radiation, and the radiobiological principles related to the CSC response to RT. Finally, we summarize the major advances and clinical trials on the development of CSC-based therapies combined with RT to overcome radioresistance. A better understanding of the potential therapeutic targets for CSC radiosensitization will provide safer and more efficient combination strategies, which in turn will improve the live expectancy and curability of cancer patients.

Current radiotherapy techniques in NSCLC: challenges and potential solutions

Introduction: Radiotherapy is an important therapeutic strategy in the management of non-small cell lung cancer (NSCLC). In recent decades, technological implementations and the introduction of image guided radiotherapy (IGRT) have significantly increased the accuracy and tolerability of radiation therapy.Area covered: In this review, we provide an overview of technological opportunities and future prospects in NSCLC management.Expert opinion: Stereotactic body radiotherapy (SBRT) is now considered the standard approach in patients ineligible for surgery, while in operable cases, it is still under debate. Additionally, in combination with systemic treatment, SBRT is an innovative option for managing oligometastatic patients and features encouraging initial results in clinical outcomes. To date, in inoperable locally advanced NSCLC, the radical dose prescription has not changed (60 Gy in 30 fractions), despite the median overall survival progressively increasing. These results arise from technological improvements in precisely hitting target treatment volumes and organ at risk sparing, which are associated with better treatment qualities. Finally, for the management of NSCLC, proton and carbon ion therapies and the recent development of MR-Linac are new, intriguing technological approaches under investigation.

Dose assessment for patients with stage I non-small cell lung cancer receiving passive scattering carbon-ion radiotherapy using daily computed tomographic images: A prospective study

BACKGROUND AND PURPOSE

This study aimed to assess dose distributions for stage I non-small cell lung cancer (NSCLC) with passive scattering carbon-ion radiotherapy (C-ion RT) using daily computed tomography (CT) images.

MATERIALS AND METHODS

We enrolled 10 patients with stage I NSCLC and acquired a total of 40 pre-fractional CT image series under the same settings as the planning CT images. These CT images were registered with planning CT images for dose evaluation using both bone matching (BM) and tumor matching (TM). Using deformable image registration, we generated accumulated doses. Moreover, the volumetric dose parameters were compared in terms of tumor coverage and lung exposure and statistical analyses were performed.

RESULTS

Overall, 25% of 40 fractional dose distributions were unacceptable with BM, compared with 2.5% with TM (P < 0.001). Using BM, three patients' accumulated dose distributions were unacceptable; however, all were satisfactory with TM (P < 0.001). No differences were observed in water-equivalent path length (WEL). The required margins in patients with poor dose distribution were 5.9 and 4.4 mm for BM and TM, respectively.

CONCLUSIONS

This study establishes that CT image-based TM is robust compared with conventional BM for both daily and accumulated dose distributions. The effects of changes in WEL seem to be limited. Hence, daily CT alignment is recommended for patients with stage I NSCLC receiving C-ion RT.

Carbon Ion Therapy: A Modern Review of an Emerging Technology

Radiation therapy is one of the most widely used therapies for malignancies. The therapeutic use of heavy ions, such as carbon, has gained significant interest due to advantageous physical and radiobiologic properties compared to photon based therapy. By taking advantage of these unique properties, carbon ion radiotherapy may allow dose escalation to tumors while reducing radiation dose to adjacent normal tissues. There are currently 13 centers treating with carbon ion radiotherapy, with many of these centers publishing promising safety and efficacy data from the first cohorts of patients treated. To date, carbon ion radiotherapy has been studied for almost every type of malignancy, including intracranial malignancies, head and neck malignancies, primary and metastatic lung cancers, tumors of the gastrointestinal tract, prostate and genitourinary cancers, sarcomas, cutaneous malignancies, breast cancer, gynecologic malignancies, and pediatric cancers. Additionally, carbon ion radiotherapy has been studied extensively in the setting of recurrent disease. We aim to provide a comprehensive review of the studies of each of these disease sites, with a focus on the current trials using carbon ion radiotherapy.

Prognostic significance of semi-quantitative FDG-PET parameters in stage I non-small cell lung cancer treated with carbon-ion radiotherapy

Purpose

Prognostic significance of volumetric ¹⁸F-fluorodeoxyglucose (FDG) positron emission tomography/computer tomography (PET/CT) parameters in carbon-ion radiotherapy (C-ion RT) treated stage I non-small cell lung cancer, and need of histology-wise separate cut-off values for risk stratification were assessed.

Methods

Thirty-nine patients (29 men and 10 women, 71.9 ± 8.3 years) who underwent FDG PET/CT examinations before C-ion RT were retrospectively evaluated. FDG-PET parameters: standardized uptake values (SUVmax, SUVpeak, and SUVmean), metabolic tumor volume (MTV), and total lesion glycolysis (TLG), and clinicopathological variables were assessed for prognosis using Cox proportional hazards regression analysis. Mann-Whitney test compared medians of significant parameters between adenocarcinoma (AC) and squamous cell carcinoma (SCC), and Kaplan-Meier curves were plotted for median-based low- and high-risk groups.

Results

Median follow-up period was 44.8 months. 1/2/3-year overall survival (OS), progression-free survival (PFS) and local control (LC) rates were 94.9/84.3/70.8, 82.1/69.2/58.4 and 97.3/85.7/82.3%. Multivariate analysis revealed age (hazard ratio, HR: 1.09; 95% confidence interval, CI: 1.0–1.19, p < 0.05) and MTV (HR 4.83, 95% CI 1.21–19.27, p < 0.03) predicted OS, and only MTV predicted PFS (HR 5.3, CI 1.32–21.35, p < 0.02) independently. Compared with AC, SCC had higher MTV (median, 6.625cm³ vs 0.2 cm³, p < 0.01). Single MTV cut-off based on overall cohort was insignificant in SCC for PFS (p > 0.02); separate cut-offs of MTV, 0.2 cm³ for AC (p < 0.03) and 6.625 cm³ for SCC (p < 0.05) were relevant.

Conclusion

Among all FDG PET/CT parameters, only MTV beared prognostic ability for stage I NSCLC treated with C-ion RT, and its histological variation may need consideration for risk-adapted therapeutic management.

Robustness of patient positioning for interfractional error in carbon ion radiotherapy for stage I lung cancer: Bone matching versus tumor matching

BACKGROUND AND PURPOSE

Patient positioning was compared by tumor matching (TM) and conventional bony structure matching (BM) in carbon ion radiotherapy for stage I non-small cell lung cancer to evaluate the robustness of TM and BM in determining interfractional error.

MATERIAL AND METHODS

Sixty irradiation fields were analyzed. Computed tomography (CT) images acquired before treatment initiation for confirmation (Conf-CT) were obtained under the same settings as the treatment planning CT images and used to evaluate both positioning methods. The dose distributions were recalculated for Conf-CT using both BM and TM, and the dose-volume histogram parameters [V_95% of clinical target volume, V_5Gy(RBE) of normal lung, and acceptance ratio (ratio of cases with V_95% > 95%)] were evaluated. The required margin, which in 90% of cases achieved the acceptable condition, was also examined.

RESULTS

Using BM and TM, the median V_95% was 98.93% and 100% (p < 0.001) and the mean V_5Gy(RBE) was 135.9 and 125.8 (p = 0.694), respectively. The estimated required margins were 7.9 and 3.3 mm and increased by 53.9% and 2.5% of V_5Gy(RBE), respectively, compared with planning.

CONCLUSIONS

TM ensured a better dose distribution than did BM. To enable TM, volumetric imaging is crucial and should replace 2D radiographs for carbon therapy of stage I lung cancer.

Hypofractionated carbon-ion radiotherapy for stage I peripheral nonsmall cell lung cancer (GUNMA0701): Prospective phase II study

This phase II study's aim was to confirm the efficacy and safety of hypofractionated carbon-ion radiotherapy in patients with stage I peripheral nonsmall cell lung cancer (NSCLC). The study encompassed 37 patients with histologically proven peripheral stage I NSCLC in the period June 2010-March 2015. All underwent the planned full dose of carbon-ion radiotherapy, administered with relative biological effectiveness of 52.8 Gy and 60 Gy (divided into four fractions over 1 week) for T1 and T2a tumors, respectively. The 2-year local control rate was set as the primary endpoint, while overall survival, progression-free survival, and the incidence rates of acute and late adverse events were secondary endpoints. The patients were followed up for 56.3 months overall and 62.2 months in the surviving patients, respectively. The actuarial local control rates were 91.2% after 2 years, and 88.1% after 5 years. No differences were found between the T1 and T2a tumors in the 5-year local control rate (90.9% vs 86.7%, P = .75). The actuarial overall survival rates achieved 91.9% for 2-year and 74.9% for 5-year period. T1 tumors showed actuarial 5-year overall survival rates of 80%, compared to 66.7% in T2a tumors. Two patients with T2a tumors and either severe emphysema or bronchiectasis experienced lung toxicity ≥ grade 2, in contrast to T1 patients who only experienced mild toxicities (lower than grade 2). The findings suggest that carbon-ion radiotherapy is effective and safe for peripheral stage I NSCLC; however, further clinical evaluations are needed to confirm its therapeutic efficacy. Trial registration: UMIN000003797. Registered 21 June 2010, prospectively registered.

Dosimetric evaluation of 4D-CBCT reconstructed by Simultaneous Motion Estimation and Image Reconstruction (SMEIR) for carbon ion therapy of lung cancer

PURPOSE

Motion management is critical for the efficacy of carbon ion therapy for moving targets such as lung tumors. We evaluated the feasibility of using four-dimensional cone beam computed tomography (4D-CBCT) reconstructed by Simultaneous Motion Estimation and Image Reconstruction (SMEIR) for dose calculation and accumulation in carbon ion treatment of lung cancer.

METHODS

Motion-compensated 4D-CBCT images were reconstructed with the SMEIR algorithm to capture the most updated anatomy and motion with an updated interphase motion model on the treatment day. Projections of all CBCT phases were simulated from the planning 4D-CT by the ray tracing technique. Treatment planning and dose calculation were performed with a GPU-based Monte Carlo dose calculation software for carbon ion therapy. The treatment plan was optimized on the average computed tomography (CT) to obtain optimal intensity of the carbon ions. From the optimized plan, dose distributions on individual phases of 4D-CT and 4D-CBCT were calculated by the Monte Carlo-based dose engine. Dose accumulation was performed on 4D-CBCT images using deformable vector fields (DVF) generated by SMEIR. The accumulated planning target volume (PTV) dose based on 4D-CBCT was then compared to the accumulated dose calculated on 4D-CT, where the DVFs between different phases were obtained by the demons deformable registration algorithm.

RESULTS

Dose value histograms (DVH) as well as absolute deviations of the maximum dose ( Δ D max ), mean dose ( Δ D mean ), and dose coverage metrics ( Δ V 95 % and Δ V 100 % ) for PTV were quantitatively evaluated for the two sets of plans. Good agreement was found between the 4D-CT and 4D-CBCT-based PTV-DVH curves. The average values of Δ D max , Δ D mean , Δ V 95 % , and Δ V 100 % calculated between the 4D-CT and SMEIR-4D-CBCT-based plans were 1.91 % , 3.55 % , 2.12%, and 1.15 % , respectively, for the PTVs of ten patient case studies.

CONCLUSIONS

Based on these results, SMEIR-reconstructed 4D-CBCTs can potentially be used for motion estimation, dose evaluation, and adaptive treatment planning in lung cancer carbon ion therapy.

A Phase I clinical trial of carbon ion radiotherapy for Stage I breast cancer: clinical and pathological evaluation

Even with its high RBE and >20 years history, there had been no breast cancer clinical trial using carbon-ion radiotherapy. We started a Phase I trial of carbon ion radiotherapy for Stage I breast cancer in 2013. This article describes the clinical and pathological evaluation of this study. Patients with low-risk Stage I breast cancer were eligible. A dose escalation study was designed, with dose levels of 48.0, 52.8 or 60.0 Gy relative biological effectiveness (RBE) administered in four fractions within 1 week. Three months after radiotherapy, the patients underwent tumor excision for pathological evaluation. Between April 2013 and December 2014, three cases receiving 48 Gy (RBE), three cases receiving 52.8 Gy (RBE) and one case receiving 60 Gy (RBE) underwent this protocol. No adverse effects were observed except for Grade 1 acute skin reaction in four cases. Pathological evaluation revealed that all four cases with doses of 52.8 Gy (RBE) and 60.0 Gy (RBE) achieved Grade 2b or more, but only two cases reached Grade 3. At the end of 2017, all cases were alive without recurrence or late had not caused any late adverse reaction. Carbon ion radiotherapy for Stage I breast cancer seems to be safe, and we found that it did not reach enough treatment effect 3 months after the treatment.

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.

Determining RBE for development of lung fibrosis induced by fractionated irradiation with carbon ions utilizing fibrosis index and high-LET BED model

BACKGROUND AND PURPOSES

Carbon ion radiotherapy (CIRT) with raster scanning technology is a promising treatment for lung cancer and thoracic malignancies. Determining normal tissue tolerance of organs at risk is of utmost importance for the success of CIRT. Here we report the relative biological effectiveness (RBE) of CIRT as a function of dose and fractionation for development of pulmonary fibrosis using well established fibrosis index (FI) model.

MATERIALS AND METHODS

Dose series of fractionated clinical quality CIRT versus conventional photon irradiation to the whole thorax were compared in C57BL6 mice. Quantitative assessment of pulmonary fibrosis was performed by applying the FI to computed tomography (CT) data acquired 24-weeks post irradiation. RBE was calculated as the ratio of photon to CIRT dose required for the same level of FI. Further RBE predictions were performed using the derived equation from high-linear energy transfer biologically effective dose (high-LET BED) model.

RESULTS

The averaged lung fibrosis RBE of 5-fraction CIRT schedule was determined as 2.75 ± 0.55. The RBE estimate at the half maximum effective dose (RBE_ED50) was estimated at 2.82 for clinically relevant fractional sizes of 1-6 Gy. At the same dose range, an RBE value of 2.81 ± 0.40 was predicted by the high-LET BED model. The converted biologically effective dose (BED) of CIRT for induction of half maximum FI (BED_ED50) was identified to be 58.12 Gy_3.95. In accordance, an estimated RBE of 2.88 was obtained at the BED_ED50 level. The LQ model radiosensitivity parameters for 5-fraction was obtained as α_H = 0.3030 ± 0.0037 Gy^-1 and β_H = 0.0056 ± 0.0007 Gy^-2.

CONCLUSION

This is the first report of RBE estimation for CIRT with the endpoint of pulmonary fibrosis in-vivo. We proposed in present study a novel way to mathematically modeling RBE by integrating RBE_max and α/β_L based on conventional high-LET BED conception. This model well predicted RBE in the clinically relevant dose range but is sensitive to the uncertainties of α/β estimates from the reference photon irradiation (α/β_L). These findings will assist to eliminate current uncertainties in prediction of CIRT induced normal tissue complications and builds a solid foundation for development of more accurate in-vivo data driven RBE estimates.

Scanned carbon-ion beam therapy throughput over the first 7 years at National Institute of Radiological Sciences

INTRODUCTION

In the 7 years since our facility opened, we have treated >2000 patients with pencil-beam scanned carbon-ion beam therapy.

METHODS

To summarize treatment workflow, we evaluated the following five metrics: i) total number of treated patients; ii) treatment planning time, not including contouring procedure; iii) quality assurance (QA) time (daily and patient-specific); iv) treatment room occupancy time, including patient setup, preparation time, and beam irradiation time; and v) daily treatment hours. These were derived from the oncology information system and patient handling system log files.

RESULTS

The annual number of treated patients reached 594, 7 years from the facility startup, using two treatment rooms. Mean treatment planning time was 6.0 h (minimum: 3.4 h for prostate, maximum: 9.3 h for esophagus). Mean time devoted to daily QA and patient-specific QA were 22 min and 13.5 min per port, respectively, for the irradiation beam system. Room occupancy time was 14.5 min without gating for the first year, improving to 9.2 min (8.2 min without gating and 12.8 min with gating) in the second. At full capacity, the system ran for 7.5 h per day.

CONCLUSIONS

We are now capable of treating approximately 600 patients per year in two treatment rooms. Accounting for the staff working time, this performance appears reasonable compared to the other facilities.

Feasibility of carbon-ion radiotherapy for re-irradiation of locoregionally recurrent, metastatic, or secondary lung tumors

Intrathoracic recurrence after carbon‐ion radiotherapy for primary or metastatic lung tumors remains a major cause of cancer‐related deaths. However, treatment options are limited. Herein, we report on the toxicity and efficacy of re‐irradiation with carbon‐ion radiotherapy for locoregionally recurrent, metastatic, or secondary lung tumors. Data of 95 patients with prior intrathoracic carbon‐ion radiotherapy who were treated with re‐irradiation with carbon‐ion radiotherapy at our institution between 2006 and 2016 were retrospectively analyzed. Seventy‐three patients (76.8%) had primary lung tumors and 22 patients (23.2%) had metastatic lung tumors. The median dose of initial carbon‐ion radiotherapy was 52.8 Gy (relative biological effectiveness) and the median dose of re‐irradiation was 66.0 Gy (relative biological effectiveness). None of the patients received concurrent chemotherapy. The median follow‐up period after re‐irradiation was 18 months. In terms of grade ≥3 toxicities, one patient experienced each of the following: grade 5 bronchopleural fistula, grade 4 radiation pneumonitis, grade 3 chest pain, and grade 3 radiation pneumonitis. The 2‐year local control and overall survival rates were 54.0% and 61.9%, respectively. In conclusion, re‐irradiation with carbon‐ion radiotherapy was associated with relatively low toxicity and moderate efficacy. Re‐irradiation with carbon‐ion radiotherapy might be an effective treatment option for patients with locoregionally recurrent, metastatic, or secondary lung tumors.

Oncogene addiction and radiation oncology: effect of radiotherapy with photons and carbon ions in ALK-EML4 translocated NSCLC

Background

Patients with Echinoderm microtubule-associated protein-like 4 (EML4)-anaplastic lymphoma kinase (ALK) positive lung cancer are sensitive to ALK-kinase inhibitors. TAE684 is a potent second generation ALK inhibitor that overcomes Crizotinib resistance. Radiotherapy is an integral therapeutic component of locally advanced lung cancer. Therefore, we sought to investigate the effects of combined radiotherapy and ALK-inhibition via TAE684 in ALK-positive vs. wild type lung cancer cells.

Methods

Human non-small cell lung cancer (NSCLC) cell lines harboring wild-type ALK (A549), EML4-ALK translocation (H3122) and murine Lewis Lung Cancer (LLC) cells were investigated. Cells were irradiated with 1–4 Gy X-Rays (320 keV) and carbon ions (Spread-out Bragg Peak, SOBP (245.4–257.0 MeV/u)) at Heidelberg Ion Therapy center. TAE684 was administered at the dose range 0–100 nM. Clonogenic survival, proliferation and apoptosis via caspase 3/7 expression level were assessed in all three cell lines using time-lapse live microscopy.

Results

TAE684 inhibited the proliferation of H3122 cells in a dose-dependent manner with a half maximal inhibitory concentration (IC₅₀) of ~ 8.2 nM. However, A549 and LLC cells were relatively resistant to TAE684 and IC₅₀ was not reached at concentrations tested (up to 100 nM) in proliferation assay. The antiproliferative effect of TAE684 was augmented by radiotherapy in H3122 cells. TAE684 significantly sensitized H3122 cells to particle therapy with carbon ions (sensitizer enhancement ratio ~1.61, p < 0.05). Caspase 3/7 activity was evidently enhanced after combination therapy in H3122 cells.

Conclusions

This is the first report demonstrating synergistic effects of combined TAE684 and radiotherapy in EML4-ALK positive lung cancer cells. In addition to conventional photon radiotherapy, ALK-inhibition also enhanced the effects of particle irradiation using carbon ions. Our data indicate beneficial effects of combined ALK-inhibition and radiotherapy in treatment of this distinct subpopulation of NSCLC that warrant further evaluation.

Enhancement of mTOR signaling contributes to acquired X-ray and C-ion resistance in mouse squamous carcinoma cell line

Our aim was to evaluate whether repetition of C‐ion (carbon ion beam) irradiation induces radioresistance as well as repeated X‐ray irradiation in cancer cell lines, and to find the key molecular pathway for radioresistance by comparing radioresistant cancer cells with their parental cells. A mouse squamous cell carcinoma cell line, NR‐S1, and radioresistant cancer cells, NR‐S1‐C30 (C30) and NR‐S1‐X60 (X60), established by repetition of C‐ion and X‐ray irradiation, respectively, were used. X‐ray and C‐ion sensitivity, changes in lysosome, mitochondria, intracellular ATP and reactive oxygen species (ROS) level, and mechanistic target of rapamycin (mTOR) signaling were evaluated. Moreover, the effect of rapamycin on radioresistance was also assessed. X‐ray and C‐ion resistance of C30 cells was moderate, and the resistance of X60 cells was the highest in this study. In X60 cells, the amount of lysosome, mitochondria, intracellular ATP and ROS level were significantly increased, and mTOR and p70S6K (ribosomal protein S6 kinase p70) phosphorylation were enhanced compared with C30 and NR‐S1 cells. The inhibition of mTOR signaling was effective for X‐ray and C‐ion radiosensitization in both cell lines, especially in X60 cells in which X‐ray and C‐ion resistance was decreased to the same level as that in NR‐S1 cells. Our results indicated that the contribution to generate X‐ray and C‐ion resistance was less for repeated C‐ion irradiations compared with repeated X‐ray irradiation. Moreover, we found that activated mTOR signaling contributes to X‐ray and C‐ion resistance in the X60 cancer cells.

Carbon-ion radiotherapy for non-small cell lung cancer with interstitial lung disease: a retrospective analysis

Background

Lung cancer is frequently complicated by interstitial lung disease (ILD). Treatment protocols for lung cancer patients with ILD have not been established; surgery, chemotherapy, and radiotherapy can all cause acute exacerbation of ILD. This study evaluated the toxicity and efficacy of carbon ion radiotherapy (CIRT) in patients with non-small cell lung cancer (NSCLC) and ILD.

Methods

Between June 2004 and November 2014, 29 patients diagnosed with NSCLC and ILD were treated with CIRT. No patient was eligible for curative surgery or conventional radiotherapy secondary to ILD. Owing to prior symptomology, radiation pneumonitis (RP) and symptom progression pre- and post-treatment were evaluated. The relationships between RP and clinical factors were investigated.

Results

Twenty-eight men and one woman, aged 62 to 90 years old, were followed for 2.7–77.1 months (median: 22.8 months). Single-grade symptomatic progression (grade 2–3) was observed in 4 patients, while 1 patient experiencedtwo-grade progression. Two patients experienced radiation-induced acute exacerbation. Local control at 3 years was 63.3% (72.2% for stage I disease); survival at 3 years was 46.3% (57.2% for stage I disease). Eighteen patients had died by the time of this writing, 10 of lung cancer progression. Radiation pneumonitis post-treatment progression correlated with dosimetric factors of the lungs (V5, V10) and a low pre-treatment serum surfactant protein-D.

Conclusions

We found that CIRT may be useful as a low-risk, curative option for NSCLC patients with ILD, a population that is typically ineligible for conventional therapy. The DVH analysis showed that minimizing the low-dose region is important for reducing the risk of severe RP.

Trial registration

NIRS-9404. Registered 1 March 1994.

Repurposing DNA repair factors to eradicate tumor cells upon radiotherapy

Cancer is the leading cause of death worldwide. Almost 50% of all cancer patients undergo radiation therapy (RT) during treatment, with varying success. The main goal of RT is to kill tumor cells by damaging their DNA irreversibly while sparing the surrounding normal tissue. The outcome of RT is often determined by how tumors recognize and repair their damaged DNA. A growing body of evidence suggests that tumors often show abnormal expression of DNA double-strand break (DSB) repair genes that are absent from normal cells. Defects in a specific DNA repair pathway make tumor cells overly dependent on alternative or backup pathways to repair their damaged DNA. These tumor cell-specific abnormalities in the DNA damage response (DDR) machinery can potentially be used as biomarkers for treatment outcomes or as targets for sensitization to ionizing radiation (IR). An improved understanding of genetic or epigenetic alterations in the DNA repair pathways specific to cancer cells has paved the way for new treatments that combine pharmacological exploitation of tumor-specific molecular vulnerabilities with IR. Inhibiting DNA repair pathways has the potential to greatly enhance the therapeutic ratio of RT. In this review, we will discuss DNA repair pathways in active cells and how these pathways are deregulated in tumors. We will also describe the impact of targeting cancer-specific aberrations in the DDR as a treatment strategy to improve the efficacy of RT. Finally, we will address the current roadblocks and future prospects of these approaches.

Prognostic analysis of radiation pneumonitis: carbon-ion radiotherapy in patients with locally advanced lung cancer

BACKGROUND

Carbon-ion radiotherapy (CIRT) is a promising treatment for locally advanced non-small-cell lung cancer, especially for patients with inoperable lung cancer. Although the incidence of CIRT-induced radiation pneumonitis (RP) ≥ grade 2 ranges from 2.5 to 9.9%, the association between CIRT-induced RP and dosimetric parameters is not clear. Herein, we identified prognostic factors associated with symptomatic RP after CIRT for patients with non-small-cell lung cancer.

METHODS

Clinical results of 65 patients treated with CIRT between 2000 and 2015 at the National Institute of Radiological Sciences were retrospectively analyzed. Clinical stage II B disease (TNM classification) was the most common stage among the patients (45%). The median radiation dose was 72 Gy (68-76) relative biological effectiveness (RBE) in 16 fractions. In cases involving metastatic lymph nodes, prophylactic irradiation of mediastinal lymph nodes was performed at a median dose of 49.5 Gy (RBE). The median follow-up was 22 months.

RESULTS

Grade 2 and grade 3 RP occurred in 6 and 3 patients (9 and 5%), respectively. No patients developed grade 4 or 5 RP. Using univariate analysis, vital capacity as a percentage of predicted (%VC), forced expiratory volume in 1 s (FEV1), mean lung dose (MLD), volume of lung receiving ≥5 Gy (RBE) (V₅), V₁₀, V₂₀ and V₃₀ were determined to be the significant predictive factors for ≥ grade 2 RP. The receiver operating characteristic (ROC) analysis revealed the cutoff values for %VC, FEV1, MLD, V₅, V₁₀, V₂₀ and V₃₀ for ≥ grade 2 RP, which were 86.9%, 1.16 L, 12.5 Gy (RBE), 28.8, 29.9, 20.1 and 15.0%, respectively. In addition, the multivariate analysis revealed that %VC <86.9% (odds ratio = 13.7; p = 0.0041) and V₃₀ ≥ 15% (odds ratio = 6.1; p = 0.0221) were significant risk factors.

CONCLUSIONS

Our study demonstrated the risk factors for ≥ grade 2 RP after carbon-ion radiotherapy for patients with locally advanced lung cancer.

Comparison of particle beam therapy and stereotactic body radiotherapy for early stage non-small cell lung cancer: A systematic review and hypothesis-generating meta-analysis

PURPOSE

To assess hypo-fractionated particle beam therapy (PBT)'s efficacy relative to that of photon stereotactic body radiotherapy (SBRT) for early stage (ES) non-small cell lung cancer (NSCLC).

METHODS

Eligible studies were identified through extensive searches of the PubMed, Medline, Google-scholar, and Cochrane library databases from 2000 to 2016. Original English publications of ES NSCLC were included. A meta-analysis was performed to compare the survival outcome, toxicity profile, and patterns of failure following each treatment.

RESULTS

72 SBRT studies and 9 hypo-fractionated PBT studies (mostly single-arm) were included. PBT was associated with improved overall survival (OS; p=0.005) and progression-free survival (PFS; p=0.01) in the univariate meta-analysis. The OS benefit did not reach its statistical significance after inclusion of operability into the final multivariate meta-analysis (p=0.11); while the 3-year local control (LC) still favored PBT (p=0.03).

CONCLUSION

Although hypo-fractionated PBT may lead to additional clinical benefit when compared with photon SBRT, no statistically significant survival benefit from PBT over SBRT was observed in the treatment of ES NSCLC in this hypothesis-generating meta-analysis after adjusting for potential confounding variables.