The impact of pre-radiotherapy surgery on radiation-induced lung injury

Clinical and Dosimetric Predictors of Radiation Pneumonitis in Patients With Non-Small Cell Lung Cancer Undergoing Postoperative Radiation Therapy

PURPOSE

Radiation pneumonitis (RP) is a common and potentially life-threatening toxicity from lung cancer radiation therapy. Data sets reporting RP rates after postoperative radiation therapy (PORT) have historically been small and with predominantly outdated field designs and radiation techniques. We examined a large cohort of patients in this context to assess the incidence and causes of RP in the modern era.

METHODS AND MATERIALS

We reviewed 285 patients with non-small cell lung cancer treated with PORT at our institution from May 2004 to January 2017. Complete dosimetric data and clinical records were reviewed and analyzed with grade 2 or higher RP as the endpoint (RP2+) (Common Terminology Criteria for Adverse Events v4.0). Patients were a median of 67 years old (range, 28-87), and most had pathologic stage III non-small cell lung cancer (91%) and received trimodality therapy (90%). Systematic dosimetric analyses using Dx increments of 5% and Vx increments of 2 Gy were performed to robustly evaluate dosimetric variables. Lung V₅ was also evaluated.

RESULTS

The incidence of RP2+ after PORT was 12.6%. Dosimetric factors most associated with RP2+ were total lungV₄ (hazard ratio [HR] 1.04, P < .001) and heart V₁₆ (HR 1.03, P = .001). On univariate analysis, the clinical factors of age (HR 1.05, P = .006) and carboplatin chemotherapy (HR 2.32, P = .012) were correlated with RP2+. On step-up multivariate analysis, only bivariate models remained significant, including lungV₅ (HR 1.037, P < .001) and age (HR 1.052, P = .011).

CONCLUSIONS

The incidence of RP after PORT is consistent with the literature. Factors correlated with RP include lung and heart doses, age, and carboplatin chemotherapy. These data also suggest that elderly patients may be more susceptible to lower doses of radiation to the lung. Based on these data, dose constraints to limit the risk of RP2+ to <5% in the setting of PORT include lungV₅ ≤65% in patients <65 years old and lungV₅ ≤36% in patients 65 years or older.

Radiation Pneumonitis: Old Problem, New Tricks

Radiation therapy is a major treatment modality for management of non-small cell lung cancer. Radiation pneumonitis is a dose limiting toxicity of radiotherapy, affecting its therapeutic ratio. This review presents patient and treatment related factors associated with the development of radiation pneumonitis. Research focusing on reducing the incidence of radiation pneumonitis by using information about lung ventilation, imaging-based biomarkers as well as normal tissue complication models is discussed. Recent advances in our understanding of molecular mechanisms underlying lung injury has led to the development of several targeted interventions, which are also explored in this review.

Proton therapy for post-operative radiation therapy of non-small cell lung cancer

Post-operative radiation therapy (PORT) is typically recommended for patients with locally advanced non-small cell lung cancer (NSCLC) with N2 mediastinal nodal involvement after surgical resection. The routine use of PORT, however, is controversial as older data demonstrated a detriment in overall survival in patients who received PORT. This detriment was thought to be due to older, more toxic radiation techniques. More recent data with modern radiation techniques demonstrates a local-regional and overall survival benefit with PORT in patients with N2 nodal involvement. Due to the competing risks of local-regional recurrence and cardiopulmonary toxicity in patients who are candidates for PORT, methods to widen the therapeutic window are needed. The physical characteristics of proton beam therapy allow for less radiation dose to the heart and lungs. Therefore, proton beam therapy has great potential in patients undergoing PORT. Initial dosimetric and clinical data have been published and are encouraging, but prospective data is needed to further understand the true benefit of proton therapy in patients undergoing PORT.

Pulmonary toxicity generated from radiotherapeutic treatment of thoracic malignancies

Radiation-induced lung injury (RILI) remains a major obstacle for thoracic radiotherapy for the treatment of lung cancer, esophageal cancer and lymphoma. It is the principal dose-limiting complication, and can markedly impair the therapeutic ratio as well as a patient's quality of life. The current review presents the relevant concepts associated with RILI, including the pathogenic mechanisms and the potential treatment strategies, so as to achieve a general understanding of this issue. RILI comprises an acute radiation pneumonitis phase and subsequent late lung fibrosis. The established assessment criteria are clinical manifestations, imaging changes and the necessity for medical assistance. Risk factors are also considered in order to optimize treatment planning. Due to the underlying molecular mechanisms of RILI, the present review also discusses several targeted pharmacological approaches for its treatment, as well as corticosteroid therapy.

Comparison of risk and predictors for early radiation pneumonitis in patients with locally advanced non-small cell lung cancer treated with radiotherapy with or without surgery

OBJECTIVES

To investigate risk and predictors for radiation pneumonitis (RP) and tolerance of lung to radiation in patients treated with thoracic radiotherapy (RT) with or without surgery.

METHODS AND MATERIALS

A total of 433 consecutive patients with locally advanced non-small cell lung cancer were followed after three-dimensional conformal radiotherapy. Among them 284 received RT without surgical intervention and 149 received postoperative radiotherapy (PORT). RP was graded according to Common Terminology Criteria for Adverse Events version 4.0.

RESULTS

The rate of grade ≥ 2 and grade ≥ 3 RP was 50 and 16% in the PORT group compared with 38 and 9% in the non-surgical group (p < 0.05 for each comparison). The lung volume was significantly smaller in PORT group than in no-surgical group (3181 ± 915 cm(3) vs. 4010 ± 1120 cm(3), p<0.05). Age, chemotherapy, mean lung dose (MLD) and planning target volume (PTV) were predictors of RP for both non-surgical group and PORT group. Mean heart dose (MHD) predicted RP in PORT group only (OR = 1.28, p = 0.003). Among patients who developed RP, V20, MLD, and MHD were significantly lower in PORT group than in no-surgical group (p < 0.05 for each comparison).

CONCLUSIONS

Except MHD predicting RP in PORT group only, most of predictors for RP were consistent in patients treated with RT with or without surgery. Patients receiving PORT had a higher risk of RP than patients receiving RT without surgery did, possibly due to decreased lung volume and lower tolerance of lung to chemoradiotherapy.

Trimodal therapy for stage III-N2 non-small-cell lung carcinoma: a single center retrospective analysis

Background

Treatment of locally advanced non-small-cell lung cancer is based on a combined approach. To study the impact of trimodal therapy for stage III-N2 NSCLC a single centre retrospective evaluation focusing on survival and therapy-related toxicity was performed.

Methods

71 patients diagnosed between March 2001 and August 2008 with pathologically confirmed stage III-N2 non-small-cell lung cancer at the University Clinic of Heidelberg were retrospectively analyzed. All patients were treated within trimodal therapy strategies including surgery, induction or adjuvant chemotherapy and postoperative radiotherapy. Overall survival (OS) and disease free survival (DFS) rates were calculated using the Kaplan-Meier method. The log-rank test and Fishers Exact test were applied for univariate analysis and Cox proportional regression model for multivariate analysis.

Results

Median survival was 32 months. 1-, 3- and 5-year overall survival (OS) rates were 84.5%, 49.6% and 35.5% respectively. Disease free survival rates at 1, 3 and 5 years were 70.4%, 41.8% and 27.4% respectively. 9 patients (12.6%) were diagnosed with a local recurrence. Multivariate analysis did not reveal any independent prognostic factors for OS, but indicated a trend for pT stage and type of surgery. In regard to toxicity 8.4% of the patients developed a clinically relevant ≥ grade 2 pneumonitis. Evaluation of the forced expiratory volume in 1 second per unit of vital capacity (FEV1/VC) before and 1-3 years post radiotherapy revealed a median decrease of 2.1%.

Conclusions

Our descriptive data indicate that trimodal therapy represents an effective and safe treatment approach for patients with stage III-N2 non-small-cell lung cancer. Further prospective clinical trials are necessary in order to clearly define the impact of multimodal strategies and optimize NSCLC treatment.

A literature-based meta-analysis of clinical risk factors for development of radiation induced pneumonitis

INTRODUCTION

The risk of developing side effects after radiotherapy is not only dependent on radiation dose, but may also be affected by patient-related risk factors. Here we perform a literature-based meta-analysis to estimate the effect of various clinical risk factors on the incidence of symptomatic radiation pneumonitis (RP).

MATERIAL AND METHODS

A systematic review of English language articles in the Pubmed, Embase and Cochrane controlled trials registers. Studies with the mesh term "radiation pneumonitis" or the search term "radiation pneumonitis" were included. Additional studies were identified by manual searching of the references. Studies reporting crude incidence or odds ratios (OR) for radiation pneumonitis vs. age, disease location, smoking status, chemotherapy schedule or comorbidity were included. A systematic overview (meta-analysis) was conducted to synthesize data across multiple studies.

RESULTS

Significant risk factors for RP were: older age (OR = 1.7, p < 0.0001); disease located in mid-lower lung (OR = 1.9, p = 0.002); presence of comorbidity (OR = 2.3, p = 0.007). Ongoing smoking was found to protect against RP (OR = 0.6, p = 0.008). History of smoking tended to protect against RP (OR = 0.7, p = 0.06). Sequential (rather than concomitant) chemotherapy scheduling (OR = 1.6, p = 0.01) increased RP risk, but treatment intensity and patients selection are likely confounders.

CONCLUSION

This systematic overview revealed several clinical risk factors for RP that have not been unambiguously identified in the literature. These risk factors should be considered when defining dose-volume constraints for radiation treatment plan optimization.

Radiation pneumonitis following yttrium-90 radioembolization: case report and literature review

Radiation-induced pneumonitis (RP) is a rare complication of radioembolization with yttrium-90 ((90)Y) microspheres. The present report describes a case of RP in a patient with liver metastases from a gastrointestinal stromal tumor after radioembolization with (90)Y glass microspheres. This patient developed clinical, functional, and radiographic findings consistent with RP, with near-complete pulmonary parenchymal recovery and no clinical evidence of relapse or progressive decline in pulmonary function over a 9-month period. As clinical use of radioembolization expands, rare adverse events such as RP may become more frequent. It is essential that interventional radiologists, radiation/medical oncologists, and nuclear medicine physicians recognize this potential complication.

Prediction of radiation pneumonitis in lung cancer patients: a systematic review

PURPOSE

Factors prediction in the development of radiation pneumonitis (RP) remains unclear. A meta-analysis about this was performed.

MATERIALS

Articles were searched in February 2012 from PubMed, EMBASE, Cochrane Library and CNKI (Chinese Journal Full-text Database) using the keywords "lung cancer," "radiation pneumonitis" or "radiation lung injury." The outcome was the RP incidence. We pooled the data using RevMan 5.1 software and tested the statistical heterogeneity.

RESULTS

We included the following factors: age, gender, weight loss, smoking history, complications, performance status, pre-radiation therapy (RT) pulmonary function, TNM, histological type, tumor location, pre-RT surgery, RT combined with chemotherapy (RCT), RT/RCT combined with amifostine, plasma end/pre-RT TGF-β1 ratio and irradiation volume. The significant risk factors for RP ≥ grade 2 were patients with chronic lung disease, tumor located in the middle or lower lobe, without pre-RT surgery, RCT, plasma end/pre-RT TGF-β1 ratio ≥1 and gross tumor volume (GTV). Following factors were identified significant for RP, including tumor located not in the upper lobe, smokers, combined with chronic lung diseases or diabetes mellitus, low pre-RT pulmonary function, RCT, RT/RCT without amifostine and plasma end/pre-RT TGF-β1 ratio ≥1. Dose-volume parameters included the average of mean lung dose (MLD) of disease lung, GTV and V (5), V (10) (≥34 %), V (20) (≥25 %), V (30) (≥18 %) of bilateral lung.

CONCLUSIONS

More attention should be paid to the levels of patients' pulmonary function, plasma TGF-β1 and dose-volume histogram (DVH). Rigorous studies are needed to identify the relationship between the above-mentioned factors and RP ≥grade 1 or 3.

Correlation of six-minute walk test, pulmonary function test and radiation pneumonitis in the management of carcinoma of oesophagus: A prospective pilot study

Purpose: To correlate six-minute walk test (6MWT) and pulmonary function test (PFT) with incidence of radiation pneumonitis (RP) while treating patients with oesophageal cancer with conformal radiotherapy.

Methods: Forty-five patients were selected to the study protocol. Pulmonary evaluation was done objectively by chest x-ray (CXR), 6MWT and PFT and subjectively by symptoms of cough, dyspnoea and fatigue. These tests were performed before radiation and then repeated at 1, 3, 6 and 9 months after treatment. The dose-volume histogram (DVH) was used to derive doses received by lung and organs at risk. χ2-test was used for calculating the p value.

Results: The walk distance change (WDC) correlated with the changes in PFT values (p = 0.001) were done at 3 and 9 months after radiation, respectively. V30 values of ≥20% correlated with the incidence of acute pneumonitis (p = 0.007). 6MVT/vital capacity (VC) values of ≤4 ft/l had a correlation with the incidence of clinically symptomatic RP at 9 months.

Conclusion: 6MWT and PFT are supplementary to each other for assessing the lung function status; but their individual role in predicting RP is weak. However, they are complementary to each other in assessing the risk of radiation-induced lung dysfunction.

Using patient data similarities to predict radiation pneumonitis via a self-organizing map

This work investigates the use of the self-organizing map (SOM) technique for predicting lung radiation pneumonitis (RP) risk. SOM is an effective method for projecting and visualizing high-dimensional data in a low-dimensional space (map). By projecting patients with similar data (dose and non-dose factors) onto the same region of the map, commonalities in their outcomes can be visualized and categorized. Once built, the SOM may be used to predict pneumonitis risk by identifying the region of the map that is most similar to a patient's characteristics. Two SOM models were developed from a database of 219 lung cancer patients treated with radiation therapy (34 clinically diagnosed with Grade 2+ pneumonitis). The models were: SOM(all) built from all dose and non-dose factors and, for comparison, SOM(dose) built from dose factors alone. Both models were tested using ten-fold cross validation and Receiver Operating Characteristics (ROC) analysis. Models SOM(all) and SOM(dose) yielded ten-fold cross-validated ROC areas of 0.73 (sensitivity/specificity = 71%/68%) and 0.67 (sensitivity/specificity = 63%/66%), respectively. The significant difference between the cross-validated ROC areas of these two models (p < 0.05) implies that non-dose features add important information toward predicting RP risk. Among the input features selected by model SOM(all), the two with highest impact for increasing RP risk were: (a) higher mean lung dose and (b) chemotherapy prior to radiation therapy. The SOM model developed here may not be extrapolated to treatment techniques outside that used in our database, such as several-field lung intensity modulated radiation therapy or gated radiation therapy.

A neural network model to predict lung radiation-induced pneumonitis

A feed-forward neural network was investigated to predict the occurrence of lung radiation-induced Grade 2+ pneumonitis. The database consisted of 235 patients with lung cancer treated using radiotherapy, of whom 34 were diagnosed with Grade 2+ pneumonitis at follow-up. The network was constructed using an algorithm that alternately grew and pruned it, starting from the smallest possible network, until a satisfactory solution was found. The weights and biases of the network were computed using the error back-propagation approach. Momentum and variable leaning techniques were used to speed convergence. Using the growing/pruning approach, the network selected features from 66 dose and 27 non-dose variables. During network training, the 235 patients were randomly split into ten groups of approximately equal size. Eight groups were used to train the network, one group was used for early stopping training to prevent overfitting, and the remaining group was used as a test to measure the generalization capability of the network (cross-validation). Using this methodology, each of the ten groups was considered, in turn, as the test group (ten-fold cross-validation). For the optimized network constructed with input features selected from dose and non-dose variables, the area under the receiver operating characteristics (ROC) curve for cross-validated testing was 0.76 (sensitivity: 0.68, specificity: 0.69). For the optimized network constructed with input features selected only from dose variables, the area under the ROC curve for cross-validation was 0.67 (sensitivity: 0.53, specificity: 0.69). The difference between these two areas was statistically significant (p = 0.020), indicating that the addition of non-dose features can significantly improve the generalization capability of the network. A network for prospective testing was constructed with input features selected from dose and non-dose variables (all data were used for training). The optimized network architecture consisted of six input nodes (features), four hidden nodes, and one output node. The six input features were: lung volume receiving > 16 Gy (V16), generalized equivalent uniform dose (gEUD) for the exponent a = 1 (mean lung dose), gEUD for the exponent a = 3.5, free expiratory volume in 1 s (FEV1), diffusion capacity of carbon monoxide (DLCO%), and whether or not the patient underwent chemotherapy prior to radiotherapy. The significance of each input feature was individually evaluated by omitting it during network training and gauging its impact by the consequent deterioration in cross-validated ROC area. With the exception of FEV1 and whether or not the patient underwent chemotherapy prior to radiotherapy, all input features were found to be individually significant (p < 0.05). The network for prospective testing is publicly available via internet access.

Predicting lung radiotherapy-induced pneumonitis using a model combining parametric Lyman probit with nonparametric decision trees

PURPOSE

To develop and test a model to predict for lung radiation-induced Grade 2+ pneumonitis.

METHODS AND MATERIALS

The model was built from a database of 234 lung cancer patients treated with radiotherapy (RT), of whom 43 were diagnosed with pneumonitis. The model augmented the predictive capability of the parametric dose-based Lyman normal tissue complication probability (LNTCP) metric by combining it with weighted nonparametric decision trees that use dose and nondose inputs. The decision trees were sequentially added to the model using a "boosting" process that enhances the accuracy of prediction. The model's predictive capability was estimated by 10-fold cross-validation. To facilitate dissemination, the cross-validation result was used to extract a simplified approximation to the complicated model architecture created by boosting. Application of the simplified model is demonstrated in two example cases.

RESULTS

The area under the model receiver operating characteristics curve for cross-validation was 0.72, a significant improvement over the LNTCP area of 0.63 (p = 0.005). The simplified model used the following variables to output a measure of injury: LNTCP, gender, histologic type, chemotherapy schedule, and treatment schedule. For a given patient RT plan, injury prediction was highest for the combination of pre-RT chemotherapy, once-daily treatment, female gender and lowest for the combination of no pre-RT chemotherapy and nonsquamous cell histologic type. Application of the simplified model to the example cases revealed that injury prediction for a given treatment plan can range from very low to very high, depending on the settings of the nondose variables.

CONCLUSIONS

Radiation pneumonitis prediction was significantly enhanced by decision trees that added the influence of nondose factors to the LNTCP formulation.

Updated assessment of the six-minute walk test as predictor of acute radiation-induced pneumonitis

PURPOSE

To assess the utility of the 6-minute walk test (6MWT) as a predictor of symptomatic radiation-induced pneumonitis (RP).

METHODS

As part of a prospective trial to study radiation-induced lung injury, 53 patients receiving thoracic radiotherapy (RT) underwent a pre-RT 6MWT, pulmonary function tests (PFTs), and had >or=3-month follow-up for prospective assessment of Grade 2 or worse RP (requiring medications or worse). Dosimetric parameters (e.g., the percentage of lung receiving >or=30 Gy) were extracted from the lung dose-volume histogram. The correlations between the 6MWT and PFT results were assessed using Pearson's correlation. The receiver operating characteristic technique was used in patient subgroups to evaluate the predictive capacities for RP of the dosimetric parameters, 6MWT results, and PFT results, or the combination (using discriminant analysis) of all three metrics. ROCKIT software was used to compare the receiver operating characteristic areas between each predictive model. The association of the decline in 6MWT with the development of RP was evaluated using Fisher's exact test.

RESULTS

The pre-RT PFT and 6MWT results correlated weakly (r = 0.44-0.57, p <or= 0.001), suggesting that they measure somewhat different physiologic functions. Of the 53 patients, 9 (17%) developed RP. The dose-volume histogram-based dosimetric parameters were the best single-metric model for predicting RP (e.g., percentage of lung receiving >or=30 Gy, receiver operating characteristic area 0.73, p = 0.03). Including the PFT or 6MWT results with the percentage of lung receiving >or=30 Gy did not improve the predictions. The predictive abilities of dosimetric-based models improved when the analysis was restricted to those patients whose tumors were not causing regional lung dysfunction. No correlation was found between the decline in the 6MWT result and the RP rate (p = 0.6).

CONCLUSION

Although the PFTs and 6MWT are related to each other, the correlation coefficients were weak, suggesting that they could be measuring different physiologic functions. In the present data set, the addition of the PFTs or 6MWT did not increase the ability of the dosimetric parameters to predict for acute symptomatic RP. Additional work is needed to better understand the interaction among the PFT results, exercise tolerance (6MWT), and the risk of RT-induced lung dysfunction.

The impact of induction chemotherapy and the associated tumor response on subsequent radiation-related changes in lung function and tumor response

PURPOSE

To assess the impact of induction chemotherapy, and associated tumor shrinkage, on the subsequent radiation-related changes in pulmonary function and tumor response.

METHODS AND MATERIALS

As part of a prospective institutional review board-approved study, 91 evaluable patients treated definitively with thoracic radiation therapy (RT) for unresectable lung cancer were analyzed. The rates of RT-associated pulmonary toxicity and tumor response were compared in the patients with and without pre-RT chemotherapy. In the patients receiving induction chemotherapy, the rates of RT-associated pulmonary toxicity and tumor response were compared in the patients with and without a response (modified Response Evaluation Criteria in Solid Tumor criteria) to the pre-RT chemotherapy. Comparisons of the rates of improvements in pulmonary function tests (PFTs) post-RT, dyspnea requiring steroids, and percent declines in PFTs post-RT were compared in patient subgroups using Fisher's exact test, analysis of variance, and linear or logistic regression.

RESULTS

The use of pre-RT chemotherapy appears to increase the rate of radiation-induced pneumonitis (p = 0.009-0.07), but has no consistent impact on changes in PFTs. The degree of induction chemotherapy-associated tumor shrinkage is not associated with the rate of subsequent RT-associated pulmonary toxicity. The degree of tumor response to chemotherapy is not related to the degree of tumor response to RT.

CONCLUSIONS

Additional study is needed to better clarify the impact of chemotherapy on radiation-associated disfunction.

Fatal pneumonitis associated with intensity-modulated radiation therapy for mesothelioma

PURPOSE

To describe the initial experience at Dana-Farber Cancer Institute/Brigham and Women's Hospital with intensity-modulated radiation therapy (IMRT) as adjuvant therapy after extrapleural pneumonectomy (EPP) and adjuvant chemotherapy.

METHODS AND MATERIALS

The medical records of patients treated with IMRT after EPP and adjuvant chemotherapy were retrospectively reviewed. IMRT was given to a dose of 54 Gy to the clinical target volume in 1.8 Gy daily fractions. Treatment was delivered with a dynamic multileaf collimator using a sliding window technique. Eleven of 13 patients received heated intraoperative cisplatin chemotherapy (225 mg/m(2)). Two patients received neoadjuvant intravenous cisplatin/pemetrexed, and 10 patients received adjuvant cisplatin/pemetrexed chemotherapy after EPP but before radiation therapy. All patients received at least 2 cycles of intravenous chemotherapy. The contralateral lung was limited to a V20 (volume of lung receiving 20 Gy or more) of 20% and a mean lung dose (MLD) of 15 Gy. All patients underwent fluorodeoxyglucose positron emission tomography (FDG-PET) for staging, and any FDG-avid areas in the hemithorax were given a simultaneous boost of radiotherapy to 60 Gy. Statistical comparisons were done using two-sided t test.

RESULTS

Thirteen patients were treated with IMRT from December 2004 to September 2005. Six patients developed fatal pneumonitis after treatment. The median time from completion of IMRT to the onset of radiation pneumonitis was 30 days (range 5-57 days). Thirty percent of patients (4 of 13) developed acute Grade 3 nausea and vomiting. One patient developed acute Grade 3 thrombocytopenia. The median V20, MLD, and V5 (volume of lung receiving 5 Gy or more) for the patients who developed pneumonitis was 17.6% (range, 15.3-22.3%), 15.2 Gy (range, 13.3-17 Gy), and 98.6% (range, 81-100%), respectively, as compared with 10.9% (range, 5.5-24.7%) (p = 0.08), 12.9 Gy (range, 8.7-16.9 Gy) (p = 0.07), and 90% (range, 66-98.3%) (p = 0.20), respectively, for the patients who did not develop pneumonitis.

CONCLUSIONS

Intensity-modulated RT treatment for mesothelioma after EPP and adjuvant chemotherapy resulted in a high rate of fatal pneumonitis when standard dose parameters were used. We therefore recommend caution in the utilization of this technique. Our data suggest that with IMRT, metrics such as V5 and MLD should be considered in addition to V20 to determine tolerance levels in future patients.