Bayesian regression analyses of radiation modality effects on pericardial and pleural effusion and survival in esophageal cancer

A Meta-Analysis and Review of Radiation Dose Escalation in Definitive Radiation Therapy between Squamous Cell Carcinoma and Adenocarcinoma of Esophageal Cancer

Esophageal cancer, ranked as the eighth most prevalent cancer globally, is characterized by a low survival rate and poor prognosis. Concurrent chemoradiation therapy (CCRT) is the standard therapy in the non-surgical treatment of localized carcinoma of the esophagus. Nevertheless, the radiation doses employed in CCRT remain notably lower compared to the curative definite chemoradiation therapy utilized in the management of other carcinomas. In order to increase the local control rates and enhance the treatment outcomes, several clinical trials have used high-dose radiation to analyze the effect of dose escalation. Despite the integration of technically advanced RT schemes such as intensity-modulated radiation therapy (IMRT), the results of these trials have failed to demonstrate a significant improvement in overall survival or local progression-free survival. In this review, we investigated previous clinical trials to determine the ineffectiveness of radiation dose escalation in the context of CCRT for esophageal cancer. We aim to clarify the factors contributing to the limited efficacy of escalated radiation doses in improving patient outcomes. Furthermore, we delve into recent research endeavors, exploring prospective radiation dose modifications being altered based on the histological characteristics of the carcinoma. The exploration of these recent studies not only sheds light on potential refinements to the existing treatment protocols but also seeks to identify novel approaches that may pave the way for more efficacious and personalized therapeutic strategies for esophageal cancer management.

Modeling the risk of radiation pneumonitis in esophageal squamous cell carcinoma treated with definitive chemoradiotherapy

BACKGROUND

To develop and validate a nomogram for the prediction of symptomatic radiation pneumonitis (RP) in patients with esophageal squamous cell carcinoma (ESCC) who received definitive concurrent chemoradiotherapy.

METHODS

Clinical factors, dose-volume histogram parameters, and pulmonary function parameters were collected from 402 ESCC patients between 2010 and 2017, including 321 patients in the primary cohort and 81 in the validation cohort. The end-point was the occurrence of symptomatic RP (grade ≥ 2) within the first 12 months after radiotherapy. Univariate and multivariate logistic regression analyses were applied to evaluate the predictive value of each factor for RP. A prediction model was generated in the primary cohort, which was internally validated to assess its performance.

RESULTS

In the primary cohort, 31 patients (9.7%) experienced symptomatic RP. Based on logistic regression model, patients with larger planning target volumes (PTVs) or higher lung V₂₀ had a higher predictive risk of RP, whereas the overall risk was substantially higher for three-dimensional conformal radiotherapy (3DCRT) than intensity-modulated radiotherapy. On multivariate analysis, independent predictive factors for RP were smoking history (P = 0.035), radiotherapy modality (P < 0.001), PTV (P = 0.039), and lung V₂₀ (P < 0.001), which were incorporated into the nomogram. The areas under the receiver operating characteristic curve of the nomogram in the primary and validation cohorts were 0.772 and 0.900, respectively, which were superior to each predictor alone.

CONCLUSIONS

Non-smoking status, 3DCRT, lung V₂₀ (> 27.5%), and PTV (≥ 713.0 cc) were significantly associated with a higher risk of RP. A nomogram was built with satisfactory prediction ability.

Development and application of an elastic net logistic regression model to investigate the impact of cardiac substructure dose on radiation-induced pericardial effusion in patients with NSCLC

BACKGROUND

Typically, cardiac substructures are neither delineated nor analyzed during radiation treatment planning. Therefore, we developed a novel machine learning model to evaluate the impact of cardiac substructure dose for predicting radiation-induced pericardial effusion (PCE).

MATERIALS AND METHODS

One-hundred and forty-one stage III NSCLC patients, who received radiation therapy in a prospective clinical trial, were included in this analysis. The impact of dose-volume histogram (DVH) metrics (mean and max dose, V5Gy[%]-V70Gy[%]) for the whole heart, left and right atrium, and left and right ventricle, on pericardial effusion toxicity (≥grade 2, CTCAE v4.0 grading) were examined. Elastic net logistic regression, using repeat cross-validation (n = 100 iterations, 75%/25% training/test set data split), was conducted with cardiac-based DVH metrics as covariates. The following model types were constructed and analyzed: (i) standard model type, which only included whole-heart DVH metrics; and (ii) a model type trained with both whole-heart and substructure DVH metrics. Model performance was analyzed on the test set using area under the curve (AUC), accuracy, calibration slope and calibration intercept. A final fitted model, based on the optimal model type, was developed from the entire study population for future comparisons.

RESULTS

Grade 2 PCE incidence was 49.6% (n = 70). Models using whole heart and substructure dose had the highest performance (median values: AUC = 0.820; calibration slope/intercept = 1.356/-0.235; accuracy = 0.743) and outperformed the standard whole-heart only model type (median values: AUC = 0.799; calibration slope/intercept = 2.456/-0.729; accuracy = 0.713). The final fitted elastic net model showed high performance in predicting PCE (median values: AUC = 0.879; calibration slope/intercept = 1.352/-0.174; accuracy = 0.801).

CONCLUSIONS

We developed and evaluated elastic net regression toxicity models of radiation-induced PCE. We found the model type that included cardiac substructure dose had superior predictive performance. A final toxicity model that included cardiac substructure dose metrics was developed and reported for comparison with external datasets.

Analysis of cardiac toxicity after definitive chemoradiotherapy for esophageal cancer using a biological dose-volume histogram

This study aimed to evaluate the relationship between cardiac toxicity after definitive chemoradiotherapy (CRT) for esophageal cancer and the dose-volume histogram (DVH) of organs at risk (OARs) [using biological effective dose (BED)]. We analyzed the data of 83 patients with esophageal cancer treated using definitive CRT between 2001 and 2016. Furthermore, we evaluated pericardial effusion (PE) as a measure of cardiac toxicity. The median total irradiation dose was 60 (50.4-71) Gy. Symptomatic PE was observed in 12 (14%) patients. The heart and pericardium V5-V100-BED were significantly higher in patients with symptomatic PE than in those without symptomatic PE (heart: V5-V95-BED, P < 0.001; V100-BED, P = 0.0053, and pericardium: V5-V40-BED, V55-V95-BED, P < 0.001; V45-50-BED, V100-BED, P < 0.05, respectively). Receiver operating characteristic curve analysis showed that the dose-volume parameter of the pericardium and the heart that was most strongly associated with an adverse cardiac event was V80-BED, and the mean dose and the cut-off value were 27.38% and 61.7 Gy-BED, respectively. Multivariate analysis showed that the pericardium V80-BED and the mean heart dose-BED were risk factors for symptomatic PE (P < 0.001, respectively). We revealed the relationship between the irradiated dose of the OARs and symptomatic PE using a BED-based dose-volume histogram. Pericardium V80-BED and mean heart dose-BED were the most relevant risk factors for symptomatic PE.

Analysis of patients scheduled for neoadjuvant therapy followed by surgery for esophageal cancer, who never made it to esophagectomy

BACKGROUND

Neoadjuvant treatment followed by esophagectomy is standard practice in locally advanced esophageal cancer. However, not all patients who started neoadjuvant treatment will undergo esophageal resection. The purpose of our study was to investigate the group of patients, scheduled for neoadjuvant treatment followed by esophagectomy, who never made it to esophageal resection.

METHODS

We retrospectively analyzed patients treated between 2002 and 2015 for locally advanced esophageal cancer, who did not undergo esophagectomy after neoadjuvant treatment. Subanalysis was performed according to time period (2002-2010 versus 2011-2015) and histology (adenocarcinoma versus squamous cell carcinoma).

RESULTS

In 114 of 679 patients (16.8%), surgery was not performed after neoadjuvant treatment. Reasons for cancelation were disease progression (50 patients, 43.9%), poor general condition (26 patients, 22.8%), irresectability (14 patients, 12.3%), patients' own decision (15 patients, 13.2%), and death during neoadjuvant treatment (9 patients, 7.9%). In the second time period, there were less irresectable tumors (17.7% versus 5.8%; p = 0.044). Median overall survival was not different over time (9.2 versus 12.5 months; p = 0.937). Irresectability (p = 0.032), patients' refusal (p = 0.012), and poor general condition (p = 0.002) were more frequent as reasons for cancelation in squamous cell carcinoma patients. Median overall survival was, respectively, 12.5 and 9.9 months for adenocarcinoma and squamous cell carcinoma patients (p = 0.441). The majority of patients refusing surgery had a clinical complete response (73.3%). They had a median overall survival of 33.2 months.

CONCLUSIONS

One in six patients starting neoadjuvant treatment for locally advanced esophageal cancer never made it to esophagectomy, more than half of them for oncological reasons, but also 1.3% because of death during treatment. Over time, irresectability as reason decreased. As a result, the relative weight of medical inoperability increased, indicating the importance of upfront testing of medical operability. Cancelation of surgery was significantly more common in patients with a squamous cell carcinoma, and this histology seems to represent a more complex oncological and functional entity. Refusal of esophagectomy based on clinical complete response showed a significant survival benefit compared to those who did not undergo esophagectomy because of other reasons.

Bayesian Semiparametric Joint Regression Analysis of Recurrent Adverse Events and Survival in Esophageal Cancer Patients

We propose a Bayesian semiparametric joint regression model for a recurrent event process and survival time. Assuming independent latent subject frailties, we define marginal models for the recurrent event process intensity and survival distribution as functions of the subject's frailty and baseline covariates. A robust Bayesian model, called Joint-DP, is obtained by assuming a Dirichlet process for the frailty distribution. We present a simulation study that compares posterior estimates under the Joint-DP model to a Bayesian joint model with lognormal frailties, a frequentist joint model, and marginal models for either the recurrent event process or survival time. The simulations show that the Joint-DP model does a good job of correcting for treatment assignment bias, and has favorable estimation reliability and accuracy compared with the alternative models. The Joint-DP model is applied to analyze an observational dataset from esophageal cancer patients treated with chemo-radiation, including the times of recurrent effusions of fluid to the heart or lungs, survival time, prognostic covariates, and radiation therapy modality.

Semi-competing risk model to predict perioperative and oncologic outcomes after radical cystectomy

Background

To utilize a semi-competing risk model to predict perioperative and oncologic outcomes after radical cystectomy and to compare the findings with the univariate Cox regression model.

Methods

We reviewed the Institutional Review Board approved database of radical cystectomy of 316 patients who had undergone robot-assisted radical cystectomy (RARC) or open radical cystectomy between 2006 and 2016. Demographic data, perioperative outcomes, complications, metastasis, and survival were analyzed. The Bayesian variable selection method was utilized to obtain models for each hazard function in the semi-competing risks.

Results

Of 316 patients treated, 48% and 18% experienced any or major complication respectively within 30 days. Intracorporeal RARC was associated with decreased metastasis risk. Extracorporeal RARC was associated with marginally decreased risks of overall complications or major complications. Patients with advanced cancer had an increased risk of metastasis, death after metastasis and death after complication. Positive nodes were associated with an increased risk of death without overall or major complications and increased risk of death after metastasis occurs. When a serious complication was taken into account there was no significant difference in mortality, irrespective of disease stage.

Conclusions

A semi-competing risk model provides relatively more accurate information in comparison to Cox regression analysis in predicting risk factors for complications and metastasis in patients undergoing radical cystectomy.

Comparison of intensity-modulated radiotherapy vs 3-dimensional conformal radiotherapy for patients with non-metastatic esophageal squamous cell carcinoma receiving definitive concurrent chemoradiotherapy: A population-based propensity-score-matched analysis

Whether the survival outcome of patients with non-metastatic esophageal squamous cell carcinoma (NM-ESCC) receiving definitive concurrent chemoradiotherapy (CCRT) is better with intensity-modulated radiotherapy (IMRT) or with 3-dimensional conformal radiotherapy (3DCRT) has been debated in the literature. We designed this population-based propensity-score (PS)-matched analysis to address this question. We identified eligible patients diagnosed between 2008 and 2015 from the Taiwan Cancer Registry and constructed a PS-matched cohort (1:1 for IMRT vs 3DCRT) to balance observable potential confounders. We compared the hazard ratio (HR) of death between IMRT and 3DCRT during the entire follow-up period. We also evaluated freedom from local regional recurrence (FFLRR) and esophageal cancer-specific survival (ECSS). Sensitivity analyses (SA) were performed to examine the robustness of our findings. Our study population constituted 558 patients who were well balanced with regard to the measured covariables. The HR of death with IMRT compared to 3DCRT was 0.43 (95% confidence interval 0.35-0.52, P < .001). The results remained significant for FFLRR and ECSS. In SA, our results remained significant when additional covariables were taken into consideration. The survival outcome of patients with NM-ESCC receiving CCRT might be better with IMRT vs 3DCRT. These study results should be interpreted with caution given some possible covariates lacking in the registry. Further studies are needed to clarify this issue.

Comparative Outcomes After Definitive Chemoradiotherapy Using Proton Beam Therapy Versus Intensity Modulated Radiation Therapy for Esophageal Cancer: A Retrospective, Single-Institutional Analysis

PURPOSE

To compare clinical outcomes between proton beam therapy (PBT) and intensity modulated radiation therapy (IMRT) in patients with esophageal cancer (EC) treated with definitive chemoradiotherapy (CRT).

METHODS AND MATERIALS

From 2007 through 2014, 343 EC patients who received definitive CRT with either PBT (n=132) or IMRT (n=211) were retrospectively analyzed. Survival, recurrence, and treatment toxicity were compared between groups. A Cox proportional hazards regression model was performed to test the association between patient/treatment variables and survival.

RESULTS

Patient/treatment variables were overall well balanced, except for age and race. Compared with IMRT, PBT had significantly better overall survival (OS; P=.011), progression-free survival (PFS; P=.001), distant metastasis-free survival (DMFS; P=.031), as well as marginally better locoregional failure-free survival (LRFFS; P=.075). No significant differences in rates of treatment-related toxicities were observed between groups. On multivariate analysis, IMRT had worse OS (hazard ratio [HR] 1.454; P=.01), PFS (HR 1.562; P=.001), and LRFFS (HR 1.461; P=.041) than PBT. Subgroup analysis by clinical stage revealed considerably higher 5-year OS (34.6% vs 25.0%, P=.038) and PFS rates (33.5% vs 13.2%, P=.005) in the PBT group for patients with stage III disease. However, no significant intergroup differences in survival were identified for stage I/II patients.

CONCLUSIONS

Compared with IMRT, PBT might be associated with improved OS, PFS, and LRFFS, especially in EC patients with locally advanced disease. These results need confirmation by prospective studies.

Recent advances in intensity modulated radiotherapy and proton therapy for esophageal cancer

INTRODUCTION

Radiotherapy is an important component of the standard of care for esophageal cancer. In the past decades, significant improvements in the planning and delivery of radiation techniques have led to better dose conformity to the target volume and improved normal tissue sparing. Areas covered: This review focuses on the advances in radiotherapy techniques and summarizes the availably dosimetric and clinical outcomes of intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy, proton therapy, and four-dimensional radiotherapy for esophageal cancer, and discusses the challenges and future development of proton therapy. Expert commentary: Although three-dimensional conformal radiotherapy is the standard radiotherapy technique in esophageal cancer, the retrospectively comparative studies strongly suggest that the dosimetric advantage of IMRT over three-dimensional conformal radiotherapy can translate into improved clinical outcomes, despite the lack of prospective randomized evidence. As a novel form of conventional IMRT technique, volumetric modulated arc therapy can produce equivalent or superior dosimetric quality with significantly higher treatment efficiency in esophageal cancer. Compared with photon therapy, proton therapy has the potential to achieve further clinical improvement due to their physical properties; however, prospective clinical data, long-term results, and cost-effectiveness are needed.

Bayesian variable selection for a semi-competing risks model with three hazard functions

A variable selection procedure is developed for a semi-competing risks regression model with three hazard functions that uses spike-and-slab priors and stochastic search variable selection algorithms for posterior inference. A rule is devised for choosing the threshold on the marginal posterior probability of variable inclusion based on the Deviance Information Criterion (DIC) that is examined in a simulation study. The method is applied to data from esophageal cancer patients from the MD Anderson Cancer Center, Houston, TX, where the most important covariates are selected in each of the hazards of effusion, death before effusion, and death after effusion. The DIC procedure that is proposed leads to similar selected models regardless of the choices of some of the hyperparameters. The application results show that patients with intensity-modulated radiation therapy have significantly reduced risks of pericardial effusion, pleural effusion, and death before either effusion type.