Advanced radiation techniques for locally advanced non-small cell lung cancer: intensity-modulated radiation therapy and proton therapy

Cardiac radiation dose is associated with inferior survival but not cardiac events in patients with locally advanced non-small cell lung cancer in the era of immune checkpoint inhibitor consolidation

PURPOSE

We assessed the association of cardiac radiation dose with cardiac events and survival post-chemoradiation therapy (CRT) in patients with locally advanced non-small cell lung cancer (LA-NSCLC) after adoption of modern radiation therapy (RT) techniques, stricter cardiac dose constraints, and immune checkpoint inhibitor (ICI) consolidation.

METHODS AND MATERIALS

This single-institution, multi-site retrospective study included 335 patients with LA-NSCLC treated with definitive, concurrent CRT between October 2017 and December 2021. All patients were evaluated for ICI consolidation. Planning dose constraints included heart mean dose < 20 Gy (<10 Gy if feasible) and heart volume receiving ≥ 50 Gy (V50Gy) < 25 %. Twenty-one dosimetric parameters for three different cardiac structures (heart, left anterior descending coronary artery [LAD], and left ventricle) were extracted. Primary endpoint was any major adverse cardiac event (MACE) post-CRT, defined as acute coronary syndrome, heart failure, coronary revascularization, or cardiac-related death. Secondary endpoints were: grade ≥ 3 cardiac events (per CTCAE v5.0), overall survival (OS), lung cancer-specific mortality (LCSM), and other-cause mortality (OCM).

RESULTS

Median age was 68 years, 139 (41 %) had baseline coronary heart disease, and 225 (67 %) received ICI consolidation. Proton therapy was used in 117 (35 %) and intensity-modulated RT in 199 (59 %). Median LAD V15Gy was 1.4 % (IQR 0-22) and median heart mean dose was 8.7 Gy (IQR 4.6-14.4). Median follow-up was 3.3 years. Two-year cumulative incidence of MACE was 9.5 % for all patients and 14.3 % for those with baseline coronary heart disease. Two-year cumulative incidence of grade ≥ 3 cardiac events was 20.4 %. No cardiac dosimetric parameter was associated with an increased risk of MACE or grade ≥ 3 cardiac events. On multivariable analysis, cardiac dose (LAD V15Gy and heart mean dose) was associated with worse OS, driven by an association with LCSM but not OCM.

CONCLUSIONS

With modern RT techniques, stricter cardiac dose constraints, and ICI consolidation, cardiac dose was associated with LCSM but not OCM or cardiac events in patients with LA-NSCLC.

The effective radiation dose to immune cells predicts lymphopenia and inferior cancer control in locally advanced NSCLC

PURPOSE

To explore the association of the effective dose to immune cells (EDIC) with disease control, lymphopenia, and toxicity in patients with non-small cell lung cancer (NSCLC) and identify methods to reduce EDIC.

METHODS

We abstracted data from all patients with locally advanced NSCLC treated with chemoradiation with or without consolidative immunotherapy over a ten-year period. Associations between EDIC and progression-free survival (PFS) and overall survival (OS) were modeled with Cox proportional hazards and Kaplan-Meier method. Logistic regression was used to model predictors of lymphopenia and higher EDIC. Analyses were performed with EDIC as a continuous and categorical variable. Lymphopenia was graded per CTCAE v5.0.

RESULTS

Overall, 786 patients were included (228 of which received consolidative immunotherapy); median EDIC was 4.7 Gy. Patients with EDIC < 4.7 Gy had a longer median PFS (15.3 vs. 9.0 months; p < 0.001) and OS (34.2 vs. 22.4 months; p < 0.001). On multivariable modeling, EDIC correlated with inferior PFS (HR 1.08, 95 % CI 1.01-1.14, p = 0.014) and OS (HR 1.10, 95 % CI 1.04-1.18, p = 0.002). EDIC was predictive of grade 4 lymphopenia (OR 1.16, 95 % CI 1.02-1.33, p = 0.026). EDIC ≥ 4.7 Gy was associated with increased grade 2 + pneumonitis (6-month incidence: 26 % vs 20 %, p = 0.04) and unplanned hospitalizations (90-day incidence: 40 % vs 30 %, p = 0.002). Compared to protons, photon therapy was associated with EDIC ≥ 4.7 Gy (OR 5.26, 95 % CI 3.71-7.69, p < 0.001) in multivariable modeling.

CONCLUSIONS

EDIC is associated with inferior disease outcomes, treatment-related toxicity, and the development of severe lymphopenia. Proton therapy is associated with lower EDIC. Further investigations to limit radiation dose to the immune system appear warranted.

Comparative Effectiveness of Intensity-Modulated Proton Therapy Versus Intensity-Modulated Radiotherapy for Patients With Inoperable Esophageal Squamous Cell Carcinoma Undergoing Curative-Intent Concurrent Chemoradiotherapy

INTRODUCTION

This study compared outcomes in patients with inoperable esophageal squamous cell carcinoma (ESCC) undergoing curative-intent concurrent chemoradiotherapy (CCRT) with intensity-modulated radiotherapy (IMRT) versus intensity-modulated proton therapy (IMPT).

METHODS

The study encompassed a retrospective cohort analysis of patients with inoperable ESCC who underwent curative-intent CCRT from January 1, 2015, to December 31, 2020, with data sourced from the Taiwan Cancer Registry Database. In this study, both IMRT and IMPT delivered a total equivalent effective dose of approximately 5040 cGy in 28 fractions, accompanied by platinum-based chemotherapy administered as per established protocols. Multivariate Cox regression analyses were performed to assess oncologic outcomes, and statistical analyses were conducted, including inverse probability of treatment-weighted and Fine and Gray method for competing risks.

RESULTS

The observed risks of ESCC-specific and all-cause mortality were lower in patients treated with IMPT compared with those treated with IMRT, with adjusted hazard ratios (aHRs) of 0.62 (95% confidence interval [CI]: 0.58-0.70) and 0.72 (95% CI: 0.66-0.80), respectively. IMPT also reduced grade 2 radiation-induced side effects, such as pneumonitis, fatigue, and major adverse cardiovascular events, with aHRs (95% CI) of 0.76 (0.66-0.82), 0.10 (0.07-0.14), and 0.70 (0.67-0.73), respectively. However, IMPT was associated with an increased risk of grade 2 radiation dermatitis, with aHR (95% CI) of 1.48 (1.36-1.60). No substantial differences were found in the incidence of radiation esophagitis between IMPT and IMRT when adjusting for covariates.

CONCLUSION

IMPT seems to be associated with superiority over IMRT in managing patients with inoperable ESCC undergoing curative-intent CCRT, suggesting improved survival outcomes and reduced toxicity. These findings have significant implications for the treatment of ESCC, particularly when surgery is not an option.

Metrics of dose to highly ventilated lung are predictive of radiation-induced pneumonitis in lung cancer patients

PURPOSE

To identify metrics of radiation dose delivered to highly ventilated lung that are predictive of radiation-induced pneumonitis.

METHODS AND MATERIALS

A cohort of 90 patients with locally advanced non-small cell lung cancer treated with standard fractionated radiation therapy (RT) (60-66 Gy in 30-33 fractions) were evaluated. Regional lung ventilation was determined from pre-RT 4-dimensional computed tomography (4DCT) using the Jacobian determinant of a B-spline deformable image registration to estimate lung tissue expansion during respiration. Multiple voxel-wise population- and individual-based thresholds for defining high functioning lung were considered. Mean dose and volumes receiving dose ≥ 5-60 Gy were analyzed for both total lung-ITV (MLD,V5-V60) and highly ventilated functional lung-ITV (fMLD,fV5-fV60). The primary endpoint was symptomatic grade 2+ (G2+) pneumonitis. Receiver operator curve (ROC) analyses were used to identify predictors of pneumonitis.

RESULTS

G2+ pneumonitis occurred in 22.2% of patients, with no differences between stage, smoking status, COPD, or chemo/immunotherapy use between G<2 and G2+ patients (P≥ 0.18). Highly ventilated lung was defined as voxels exceeding the population-wide median of 18% voxel-level expansion. All total and functional metrics were significantly different between patients with and without pneumonitis (P≤ 0.039). Optimal ROC points predicting pneumonitis from functional lung dose were fMLD ≤ 12.3 Gy, fV5 ≤ 54% and fV20 ≤ 19 %. Patients with fMLD ≤ 12.3 Gy had a 14% risk of developing G2+ pneumonitis whereas risk significantly increased to 35% for those with fMLD > 12.3 Gy (P = 0.035).

CONCLUSIONS

Dose to highly ventilated lung is associated with symptomatic pneumonitis and treatment planning strategies should focus on limiting dose to functional regions. These findings provide important metrics to be used in functional lung avoidance RT planning and designing clinical trials.

Death without progression as an endpoint to describe cardiac radiation effects in locally advanced non-small cell lung cancer

Background and purpose

Prior studies have examined associations of cardiovascular substructure dose with overall survival (OS) or cardiac events after chemoradiotherapy (CRT) for non-small cell lung cancer (NSCLC). Herein, we investigate an alternative endpoint, death without cancer progression (DWP), which is potentially more specific than OS and more sensitive than cardiac events for understanding CRT toxicity.

Materials and methods

We retrospectively reviewed records of 187 patients with locally advanced or oligometastatic NSCLC treated with definitive CRT from 2008 to 2016 at a single institution. Dosimetric parameters to the heart, lung, and ten cardiovascular substructures were extracted. Charlson Comorbidity Index (CCI), excluding NSCLC diagnosis, was used to stratify patients into CCI low (0-2; n = 66), CCI intermediate (3-4; n = 78), and CCI high (≥5; n = 43) groups. Primary endpoint was DWP, modeled with competing risk regression. Secondary endpoints included OS. An external cohort consisted of 140 patients from another institution.

Results

Median follow-up was 7.3 years for survivors. Death occurred in 143 patients (76.5 %), including death after progression in 118 (63.1 %) and DWP in 25 (13.4 %). On multivariable analysis, increasing CCI stratum and mean heart dose were associated with DWP. For mean heart dose ≥ 10 Gy vs < 10 Gy, DWP was higher (5-year rate, 16.9 % vs 6.7 %, p = 0.04) and OS worse (median, 22.9 vs 34.1 months, p < 0.001). Ventricle (left, right, and bilateral) and pericardial but not atrial substructure dose were associated with DWP, whereas all three were inversely associated with OS. Cutpoint analysis identified right ventricle mean dose ≥ 5.5 Gy as a predictor of DWP. In the external cohort, we confirmed an association of ventricle, but not atrial, dose with DWP.

Conclusion

Cardiovascular substructure dose showed distinct associations with DWP. Future cardiotoxicity studies in NSCLC could consider DWP as an endpoint.

Cardiovascular Toxicity and Risk Mitigation with Lung Cancer Treatment

PURPOSE OF REVIEW

Patients with lung cancer often have concomitant cardiovascular comorbidities and receive potentially cardiotoxic therapies. As oncologic outcomes improve, the relative impact of cardiovascular disease on lung cancer survivors is expected to increase. This review summarizes cardiovascular toxicities observed after treatment for lung cancer, as well as recommended risk mitigation strategies.

RECENT FINDINGS

A variety of cardiovascular events may be observed after surgery, radiation therapy (RT), and systemic therapy. The risk of cardiovascular events after radiation therapy (RT) is higher than previously appreciated (23-32%), and RT dose to the heart is a modifiable risk factor. Targeted agents and immune checkpoint inhibitors have been associated with cardiovascular toxicities distinct from those of cytotoxic agents; these are rare but can be severe and require prompt intervention. Optimization of cardiovascular risk factors is important at all phases of cancer therapy and survivorship. Recommended practices for baseline risk assessment, preventive measures, and appropriate monitoring are discussed herein.

LINC01224 facilitates the proliferation and inhibits the radiosensitivity of melanoma cells through the miR-193a-5p/NR1D2 axis

Melanoma is a skin cancer characterized by early metastasis and high mortality. Radiotherapy is a common treatment for melanoma in patients. Long noncoding RNAs play pivotal roles in regulating the radiosensitivity of many tumors, including melanomas. In this study, the role of LINC01224 in the radiosensitivity of melanoma cells was explored. The expression of LINC01224 in melanoma was examined by reverse transcription-quantitative polymerase chain reaction, and the results showed that LINC01224 was upregulated in melanoma tissues and cells. The effects of LINC01224 on cell proliferation and apoptosis in melanoma were assessed by 3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide (MTT), colony formation, and flow cytometry assays. The effects of LINC01224 on the radiosensitivity of melanoma were analyzed by colony formation assay. The results implied that LINC01224 knockdown inhibited cell viability and proliferation but enhanced cell apoptosis and radiosensitivity. Luciferase reporter and RNA pull-down assays were performed to evaluate the relationships between LINC01224 and miR-193a-5p or miR-193a-5p and nuclear receptor subfamily 1 group D member 2 (NR1D2). We found that LINC01224 binds to miR-193a-5p, which directly targets NR1D2. In addition, we discovered that LINC01224 upregulated NR1D2 expression by sponging miR-193a-5p in melanoma cells. Overall, the data collected in this study suggest that LINC01224 exerts oncogenic effects in melanoma via the miR-193a-5p/NR1D2 axis.

Surgical complications and clinical outcomes after dose-escalated trimodality therapy for non-small cell lung cancer in the era of intensity-modulated radiotherapy

BACKGROUND

Trimodality therapy (TMT) with preoperative chemoradiation followed by surgical resection is used for locally-advanced non-small-cell lung cancer (LA-NSCLC). Traditionally, preoperative radiation doses ≤54 Gy are used due to concerns regarding excess morbidity, but little is known about outcomes and toxicities after TMT with intensity-modulated radiotherapy (IMRT) to higher doses.

METHODS

A retrospective analysis of patients who received planned TMT with IMRT for LA-NSCLC at Brigham and Women's Hospital/Dana-Farber Cancer Institute between 2008 and 2017 was performed. Clinical and treatment characteristics, pathologic response, and surgical toxicity were assessed. Kaplan-Meier method and log-rank test was used for survival outcomes. Cox proportional-hazards regression was used for multivariable analysis.

RESULTS

Forty-six patients received less than definitive doses of <60 Gy and 30 patients received definitive doses ≥60 Gy. Surgical outcomes, pathologic complete response, and postoperative toxicity did not differ significantly between the groups. With median follow-up of 3.6 years (range: 0.4-11.4), three-year locoregional recurrence-free survival (78.0% vs. 68.3%, p = 0.51) and overall survival (OS) (61.0% vs. 69.4%, p = 0.32) was not significantly different between patients receiving <60 Gy and ≥60 Gy, respectively. On multivariable analysis, older age, clinical stage, and length of hospital stay (LOS) >7 days were associated with OS.

CONCLUSIONS

With IMRT, there was no increased rate of surgical complications in patients receiving higher doses of radiation. Survival outcomes or LOS did not differ based on radiation dose, but increased LOS was associated with worse OS. Larger prospective studies are needed to further examine outcomes after IMRT in patients with LA-NSCLC receiving TMT.

Effect of Intensity Modulated Radiotherapy (IMRT) on the immunity, physical status and clinical effect of locally advanced NSCLC patients

Objectives:

To evaluate the clinical value of radiotherapy combined with Camrelizumab in treating locally advanced non-small cell lung cancer (NSCLC) patients.

Methods:

80 locally advanced NSCLC patients were randomly divided into two groups (n=40). The control group was administered with intensity modulated radiation therapy (IMRT), whereas the experimental group with Camrelizumab in addition to IMRT. All the patients underwent clinical efficacy evaluation in terms of adverse drug reaction (ADR), physical status improvement after the treatment, and changes in T lymphocyte subpopulations (incl. CD3⁺, CD4⁺, CD8⁺, CD4⁺/CD8⁺).

Results:

The efficacy was found to be 70% and 47.5 in experimental group and control group, respectively, with the former being significantly better than the latter (p=0.03). The ADR rates were 50% and 37.5% in the experimental group and control group, respectively; but the difference remained insignificant (p=0.26). As for physical status improvement, experimental group evidently excelled the control group (p=0.04). The post-treatment indicators such as CD3⁺, CD4⁺, CD8⁺, CD4⁺/CD8⁺ were significantly more improved in the experimental group than the control group (CD3⁺, p=0.02; CD4⁺, p=0.00; and CD4⁺/CD8⁺, p=0.01). However, the changes in CD8+ were not significant at all (p=0.46).

Conclusions:

The combined therapy of IMRT with Camrelizumab appeared effective in dealing with the locally advanced NSCLC patients, as such patients presented significantly better immune state and physical status improvement but not increased ADR. The therapy is both safe and effective.

LncRNA CCAT1 downregulation increases the radiosensitivity of non-small cell lung cancer cells

This study aims to investigate if the radiosensitivity of non-small cell lung cancer (NSCLC) cells can be regulated by long noncoding RNA (lncRNA) colon cancer associated transcript1 (CCAT1). CCAT1 was detected by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) in NSCLC cells (A549, H1299, SK-MES1, H460, and H647) and human bronchial epithelial cells (16HBE). H460 and A549 cells were then selected for the determination of CCAT1 expression after exposure to radiation (0, 2, 4, 6 Gy) at different time points (0, 6, 12, 24 h). Colony forming assay was performed to evaluate the effects of CCAT1 siRNA or pcDNA3.1-CCAT1 vector on the radiosensitivity of H460 and A549 cells. Then, flow cytometry, western blotting and qRT-PCR were also conducted. CCAT1 was increased in NSCLC cells when compared with 16HBE cells, which was declined in a time- and dosage-dependent manner after exposure to radiation. The H460 and A549 cell colonies were decreased and the γ-H2AX expression was elevated with the increase of radiation dosage, which was more obvious in those transfected with CCAT1 siRNA. CCAT1 downregulation arrested NSCLC cells at G2/M phase. Moreover, the enhanced apoptosis of radiotherapy-treated NSCLC cells with reductions of p-p38/p38, p-ERK/ERK, and p-JNK/JNK was promoted by siCCAT1, but it was reversed by pcDNA3.1-CCAT1 vector. Inhibiting CCAT1 regulated cell cycle, DNA damage and apoptosis of NSCLC cells, and affected MAPK pathway, eventually improving the radiosensitivity of NSCLC.

Biology of Radiation-Induced Lung Injury

Radiation-induced lung injury encompasses radiation-induced pneumonitis, inflammation of the lung which may manifest as a dose-limiting acute or subacute toxicity, and radiation-induced lung fibrosis, a late effect of lung exposure to radiation. This review aims to highlight developments in molecular radiation biology of radiation-induced lung injury and their implications in clinical practice.

Radiation Modalities Used in Lung Cancer: An Overview for Thoracic Surgeons

Radiation is a constantly evolving technology which plays a role in the management of lung cancer in a variety of settings: as an adjunct to surgery, definitively, and palliatively. Key aspects of radiation oncology-including acute and chronic toxicities of thoracic radiation and rationale for choosing one modality of radiation over another-may be obscure to those outside the field. We aim to provide a useful overview relevant for the thoracic surgeon of radiation technology and delivery. A review was performed of salient articles identifying radiation technologies used in lung cancer which were summarized and expounded upon with focus on integrating their history, evolution, and landmark trials establishing basis of their use. This article reviews the four fundamental means of external beam radiation employed in managing lung cancer and provides visual examples of comparison plans. We also touch on potential practice-changing developments in regards to proton therapy and radiation in the era of immunotherapy. Radiation oncology has evolved considerably over time to become a critical part of lung cancer management, particularly in early-stage inoperable disease and locally advanced disease. Maximizing tumor control while minimizing toxicity drives treatment strategies. Knowledge of these fundamentals will help the thoracic surgeon answer many questions patients pose regarding radiation.

Is IMRT or VMAT superior or inferior to 3D conformal therapy in the treatment of lung cancer? A brief literature review

Aim:

To identify treatment outcome, dose uniformity, treatment time, toxicity among 3D conformal therapy (3D-CRT), intensity-modulated radiation therapy (IMRT), volumetric-modulated arc therapy (VMAT) for non-small-cell lung cancer (NSCLC) based on literature review.

Methods:

A literature search was conducted using PubMed/MEDLINE, BMC—part of Springer Nature, Google Scholar and iMEDPub Ltd with the following keywords for filtering: 3D-CRT, IMRT, VMAT, lung cancer, local control and radiobiology. A total of 14 publications were finally selected for the comparison of 3D-CRT, IMRT and VMAT to determine which technique is superior or inferior among these three.

Results:

Compared to 3D-CRT, IMRT delivers more precise treatment, has better conformal dose coverage to planning target volume (PTV) that covers gross tumour with microscopic extension, respiratory tumour motion and setup margin. 3D-CRT has large number of limitations: low overall survival (OS), large toxicity, secondary malignancies.

Conclusions:

It is difficult to choose the best technique for treating NSCLC due to patient conditions and technique availability. A high-precision treatment may improve tumour control probability (TCP) and patient’s quality of life. VMAT, whether superior or not, needs more clinical trials to treat NSCLC and requires longer dose optimisation time with the greatest benefit of rapid treatment delivery, improved patient comfort, reduced intrafraction motion and increased patient throughput compared to IMRT and 3D-CRT.

Radiation Induces Pulmonary Fibrosis by Promoting the Fibrogenic Differentiation of Alveolar Stem Cells

The lung is a radiosensitive organ, which imposes limits on the therapeutic dose in thoracic radiotherapy. Irradiated alveolar epithelial cells promote radiation-related pneumonitis and fibrosis. However, the role of lung stem cells (LSCs) in the development of radiation-induced lung injury is still unclear. In this study, we found that both LSCs and LSC-derived type II alveolar epithelial cells (AECII) can repair radiation-induced DNA double-strand breaks, but the irradiated LSCs underwent growth arrest and cell differentiation faster than the irradiated AECII cells. Moreover, radiation drove LSCs to fibrosis as shown with the elevated levels of markers for epithelial-mesenchymal transition and myofibroblast (α-smooth muscle actin (α-SMA)) differentiation in in vitro and ex vivo studies. Increased gene expressions of connective tissue growth factor and α-SMA were found in both irradiated LSCs and alveolar cells, suggesting that radiation could induce the fibrogenic differentiation of LSCs. Irradiated LSCs showed an increase in the expression of surfactant protein C (SP-C), the AECII cell marker, and α-SMA, and irradiated AECII cells expressed SP-C and α-SMA. These results indicated that radiation induced LSCs to differentiate into myofibroblasts and AECII cells; then, AECII cells differentiated further into either myofibroblasts or type I alveolar epithelial cells (AECI). In conclusion, our results revealed that LSCs are sensitive to radiation-induced cell damage and may be involved in radiation-induced lung fibrosis.

Proton beam therapy delivered using pencil beam scanning vs. passive scattering/uniform scanning for localized prostate cancer: Comparative toxicity analysis of PCG 001-09

Background and purpose

Patient-level benefits of proton beam therapy (PBT) relative to photon therapy for prostate cancer (PC) continue to be the focus of debate. Although trials comparing the two modalities are underway, most are being conducted using "conventional" PBT (passive scattering/uniform scanning [PS/US]) rather than pencil beam scanning (PBS). The dosimetric benefits of PBS are well-known, but comparative data are limited. This analysis compares PBS toxicity rates with those of PS/US in a prospective multicenter registry.

Methods

We evaluated acute/late gastrointestinal (GI) and genitourinary (GU) toxicity rates for men with low-to-intermediate risk PC enrolled in PCG 001-09. Acute toxicities with the two techniques were compared using χ² tests, and the cumulative incidence methods for late toxicity. Multivariable analyses (MVAs) for acute toxicity were performed using logistic regression, and cox proportional hazards models for late toxicity.

Results

Patients were treated using PS/US (n = 1105) or PBS (n = 238). Acute grade ≥2 GI toxicity in PBS did not significantly differ from that with PS/US (2.9% and 2.1%, respectively; P = 0.47). Acute grade ≥2 GU toxicity was significantly higher with PBS (21.9% and 15.1%; P < 0.01). In MVA, PBS was significantly associated with increased acute grade ≥2 GU toxicity (RR = 1.57, p < 0.001). Late grade ≥2 GI and GU toxicities did not differ significantly between groups.

Conclusions

This is the first multi-institutional comparative effectiveness evaluation of PBT techniques in PC. Differences in acute GU toxicity warrant further evaluation, and highlight the urgent need for prospective data using PBT.

Early Outcomes of Patients With Locally Advanced Non-small Cell Lung Cancer Treated With Intensity-Modulated Proton Therapy Versus Intensity-Modulated Radiation Therapy: The Mayo Clinic Experience

Purpose

There are very little data available comparing outcomes of intensity-modulated proton therapy (IMPT) to intensity-modulated radiation therapy (IMRT) in patients with locally advanced NSCLC (LA-NSCLC).

Methods

Seventy-nine consecutively treated patients with LA-NSCLC underwent definitive IMPT (n = 33 [42%]) or IMRT (n = 46 [58%]) from 2016 to 2018 at our institution. Survival rates were calculated using the Kaplan-Meier method and compared with the log-rank test. Acute and subacute toxicities were graded based on Common Terminology Criteria for Adverse Events, version 4.03.

Results

Median follow-up was 10.5 months (range, 1-27) for all surviving patients. Most were stage III (80%), received median radiation therapy (RT) dose of 60 Gy (range, 45-72), and had concurrent chemotherapy (65%). At baseline, the IMPT cohort was older (76 vs 69 years, P < .01), were more likely to be oxygen-dependent (18 vs 2%, P = .02), and more often received reirradiation (27 vs 9%, P = .04) than their IMRT counterparts. At 1 year, the IMPT and IMRT cohorts had similar overall survival (68 vs 65%, P = .87), freedom from distant metastasis (71 vs 68%, P = .58), and freedom from locoregional recurrence (86 vs 69%, P = .11), respectively. On multivariate analyses, poorer pulmonary function and older age were associated with grade +3 toxicities during and 3 months after RT, respectively (both P ≤ .02). Only 5 (15%) IMPT and 4 (9%) IMRT patients experienced grade 3 or 4 toxicities 3 months after RT (P = .47). There was 1 treatment-related death from radiation pneumonitis 6 months after IMRT in a patient with idiopathic pulmonary fibrosis.

Conclusions

Compared with IMRT, our early experience suggests that IMPT resulted in similar outcomes in a frailer population of LA-NSCLC who were more often being reirradiated. The role of IMPT remains to be defined prospectively.