Intensity-Modulated Radiotherapy, Not 3 Dimensional Conformal, Is the Preferred Technique for Treating Locally Advanced Disease With High-Dose Radiotherapy: The Argument Against

Incidence and Risk Factors of Symptomatic Radiation Pneumonitis in Non-Small-Cell Lung Cancer Patients Treated with Concurrent Chemoradiotherapy and Consolidation Durvalumab

INTRODUCTION

Data on the risk factors for symptomatic radiation pneumonitis (RP) in non-small-cell lung cancer (NSCLC) patients treated with concurrent chemoradiotherapy (CCRT) and consolidation durvalumab are limited; we aimed to investigate these risk factors.

MATERIALS AND METHODS

This multicenter retrospective study, conducted at 15 institutions in Japan, included patients who were ≥20 years of age; who started definitive CCRT for NSCLC between July 1, 2018, and July 31, 2019; and who then received durvalumab. The primary endpoint was grade 2 or worse (grade 2+) RP.

RESULTS

In the 146 patients analyzed, the median follow-up period was 16 months. A majority of the patients had stage III disease (86%), received radiation doses of 60 to 66 Gy equivalent in 2-Gy fractions (93%) and carboplatin and paclitaxel/nab-paclitaxel (77%), and underwent elective nodal irradiation (71%) and 3-dimensional conformal radiotherapy (75%). RP grade 2 was observed in 44 patients (30%); grade 3, in four patients (3%); grade 4, in one patient (1%); and grade 5, in one patient (1%). In the multivariable analysis, lung V20 was a significant risk factor, whereas age, sex, smoking history, irradiation technique, and chemotherapy regimen were not. The 12-month grade 2+ RP incidence was 34.4% (95% confidence interval [CI], 26.7%-42.1%); the values were 50.0% (95% CI, 34.7%-63.5%) and 27.1% (95% CI, 18.8%-36.2%) in those with lung V20 ≥ 26% and < 26%, respectively (P = .007).

CONCLUSION

The incidence of grade 2+ RP was relatively high in this multicenter real-world study, and its risk increased remarkably at elevated lung V20. Our findings can aid in RP risk prediction and the safe radiotherapy treatment planning.

Development and validation of a decision support tool to select IMRT as radiotherapy treatment planning modality for patients with locoregionally advanced non-small cell lung cancers (NSCLC)

OBJECTIVE:

Radiation planning for locally-advanced non-small cell lung cancer (NSCLC) can be time-consuming and iterative. Many cases cannot be planned satisfactorily using multisegment three-dimensional conformal radiotherapy (3DCRT). We sought to develop and validate a predictive model which could estimate the probability that acceptable target volume coverage would need intensity modulated radiotherapy (IMRT).

METHODS:

Variables related to the planning target volume (PTV) and topography were identified heuristically. These included the PTV, it's craniocaudal extent, the ratio of PTV to total lung volume, distance of the centroid of the PTV from the spinal canal, and the extent PTV crossed the midline. Metrics were chosen such that they could be measured objectively, quickly and reproducibly. A logistic regression model was trained and validated on 202 patients with NSCLC. A group of patients who had both complex 3DCRT and IMRT planned was then used to derive the utility of the use of such a model in the clinic based on the time taken for planning such complex 3DCRT.

RESULTS:

Of the 202 patients, 93 received IMRT, as they had larger volumes crossing midline. The final model showed a good rank discrimination (Harrell's C-index 0.84) and low calibration error (mean absolute error of 0.014). Predictive accuracy in an external dataset was 92%. The final model was presented as a nomogram. Using this model, the dosimetrist can save a median planning time of 168 min per case.

CONCLUSION:

We developed and validated a data-driven, decision aid which can reproducibly determine the best planning technique for locally-advanced NSCLC.

ADVANCES IN KNOWLEDGE:

Our validated, data-driven decision aid can help the planner to determine the need for IMRT in locally advanced NSCLC saving significant planning time in the process.

Phase II Study of a Radiotherapy Total Dose Increase in Hypoxic Lesions Identified by 18F-Misonidazole PET/CT in Patients with Non-Small Cell Lung Carcinoma (RTEP5 Study)

See an invited perspective on this article on page 1043.This multicenter phase II study investigated a selective radiotherapy dose increase to tumor areas with significant ¹⁸F-misonidazole (¹⁸F-FMISO) uptake in patients with non-small cell lung carcinoma (NSCLC). Methods: Eligible patients had locally advanced NSCLC and no contraindication to concomitant chemoradiotherapy. The ¹⁸F-FMISO uptake on PET/CT was assessed by trained experts. If there was no uptake, 66 Gy were delivered. In ¹⁸F-FMISO-positive patients, the contours of the hypoxic area were transferred to the radiation oncologist. It was necessary for the radiotherapy dose to be as high as possible while fulfilling dose-limiting constraints for the spinal cord and lungs. The primary endpoint was tumor response (complete response plus partial response) at 3 mo. The secondary endpoints were toxicity, disease-free survival (DFS), and overall survival at 1 y. The target sample size was set to demonstrate a response rate of 40% or more (bilateral α = 0.05, power 1-β = 0.95). Results: Seventy-nine patients were preincluded, 54 were included, and 34 were ¹⁸F-FMISO-positive, 24 of whom received escalated doses of up to 86 Gy. The response rate at 3 mo was 31 of 54 (57%; 95% confidence interval [CI], 43%-71%) using RECIST 1.1 (17/34 responders in the ¹⁸F-FMISO-positive group). DFS and overall survival at 1 y were 0.86 (95% CI, 0.77-0.96) and 0.63 (95% CI, 0.49-0.74), respectively. DFS was longer in the ¹⁸F-FMISO-negative patients (P = 0.004). The radiotherapy dose was not associated with DFS when adjusting for the ¹⁸F-FMISO status. One toxic death (66 Gy) and 1 case of grade 4 pneumonitis (>66 Gy) were reported. Conclusion: Our approach results in a response rate of 40% or more, with acceptable toxicity. ¹⁸F-FMISO uptake in NSCLC patients is strongly associated with poor prognosis features that could not be reversed by radiotherapy doses up to 86 Gy.

Intensity-Modulated Radiation Therapy May Improve Local-Regional Tumor Control for Locally Advanced Non-Small Cell Lung Cancer Compared With Three-Dimensional Conformal Radiation Therapy

BACKGROUND

Consistent results are lacking as regards the comparative effectiveness of intensity-modulated radiotherapy (IMRT) versus three-dimensional conformal radiotherapy (3DCRT) in patients with locally advanced non-small cell lung cancer (LA-NSCLC).

PATIENTS AND METHODS

Patients treated with definitive radiotherapy (RT) between 2002 and 2010 were retrospectively reviewed. Overall survival (OS), local-regional progression-free survival (LRPFS), distant metastasis-free survival (DMFS), and progression-free survival (PFS) were compared among patients irradiated with different techniques. The association between RT technique and survival indexes was assessed in a Cox proportional hazard regression model. Propensity score matching (PSM) was used to balance known confounding factors.

RESULTS

A total of 652 patients were eligible for analysis, including 206 with 3DCRT and 446 with IMRT. The median OS of the 3DCRT and IMRT groups were 19.4 and 23.3 months, with the 5-year rate of 13% and 19%, respectively (p = .043). Multivariate analysis identified IMRT as an independent favorable factor associated with LRPFS and DMFS. PSM analysis further verified the beneficial effect of IMRT on LRPFS. No difference in OS or PFS was observed between the two techniques. Subgroup analysis revealed that IMRT might be differentially more effective in both OS and LRPFS among patients who were female, nonsmokers, with adenocarcinoma, or without weight loss. There was a significant reduction of lung toxicity and similar esophagus toxicity in the IMRT group when compared with the 3DCRT group.

CONCLUSION

IMRT may confer superior LRPFS and comparable OS than can be achieved with 3DCRT in LA-NSCLC, along with the reduction of pulmonary toxicity.

IMPLICATIONS FOR PRACTICE

Based on the largest number of patients from a single institution, the present study demonstrated that intensity-modulated radiotherapy (IMRT) could provide superior local-regional progression-free survival and similar overall survival compared with the traditional three-dimensional conformal radiotherapy (3DCRT) for stage III non-small cell lung cancer (NSCLC). IMRT was also found to be associated with the significantly decreased incidence of pulmonary toxicity. These results suggest that IMRT should be considered a surrogate for 3DCRT in locally advanced NSCLC and might be the preferred option for a female nonsmoker with adenocarcinoma and a potentially high risk of pulmonary toxicity from radiotherapy.

Visualization of complex DNA double-strand breaks in a tumor treated with carbon ion radiotherapy

Carbon ion radiotherapy shows great potential as a cure for X-ray-resistant tumors. Basic research suggests that the strong cell-killing effect induced by carbon ions is based on their ability to cause complex DNA double-strand breaks (DSBs). However, evidence supporting the formation of complex DSBs in actual patients is lacking. Here, we used advanced high-resolution microscopy with deconvolution to show that complex DSBs are formed in a human tumor clinically treated with carbon ion radiotherapy, but not in a tumor treated with X-ray radiotherapy. Furthermore, analysis using a physics model suggested that the complexity of radiotherapy-induced DSBs is related to linear energy transfer, which is much higher for carbon ion beams than for X-rays. Visualization of complex DSBs in clinical specimens will help us to understand the anti-tumor effects of carbon ion radiotherapy.

Assessing the Impact of Postoperative Radiation Therapy for Completely Resected Limited-Stage Small Cell Lung Cancer Using the National Cancer Database

INTRODUCTION

Surgical resection is being increasingly used for early-stage small cell lung cancer (SCLC). However, there are sparse data regarding the role of adjuvant therapies, particularly postoperative radiation therapy (PORT). We investigated the impact of PORT on survival after complete surgical resection for SCLC using the National Cancer Database.

METHODS

There were 3017 patients diagnosed with nonmetastatic SCLC between 1998 and 2011 who underwent R0 sublobar resection, lobectomy, or pneumonectomy. Patients were stratified by the use of PORT, and only those who received a minimum dose of 45 Gy were included. The overall survival (OS) of patients based on PORT use were analyzed by Kaplan-Meier analysis and compared using the log-rank test. Multivariate Cox regression analysis was used to identify factors associated with survival.

RESULTS

For the entire study population, the 5-year OS was significantly poorer with the addition of PORT (33.9% versus 40.6%; p = 0.005). When analyzed by subgroup, patients with pN0 stage had significantly decreased OS with PORT (39.3% versus 46.3%; p = 0.07) and patients with pN2 stage had significantly improved OS with PORT (29.0% versus 18.6%; p < 0.001). No differences in OS were observed in patients with pN1 stage. On multivariate analysis, the hazard ratio for PORT in pN0 disease was 1.36 (95% confidence interval, 1.09-1.70; p < 0.001) and the hazard ratio for PORT in pN2 disease was 0.60 (95% confidence interval, 0.45-0.80; p < 0.001).

CONCLUSION

The use of PORT was associated with a deleterious effect on OS in patients with pN0 disease but significantly improved OS in patients with pN2 disease.