The Effect of Radiation on Overall Survival among Metastatic Prostate Cancer Patients treated by ADT as the first-line treatment Open Access

Zhou, Jingru (Spring 2020)

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Background: STAMPEDE (Systemic Therapy in Advancing or Metastatic Prostate Cancer: Evaluation of Drug efficacy) is a large clinical trail that conducted to evaluate nova treatment methods for patients suffered from high-risk prostate cancer. Our goal is to identify a subgroup of these patients who may benefit from radiation therapy in the National Cancer Data Base (NCDB) to avoid unwarranted use of radiotherapy in patients.

Methods: Patients with newly diagnosed metastatic prostate cancer were identified according to STAMPEDE trial exclusion and inclusion criteria. We compared the overall survival (OS) of patients who received radiation therapy and those who did not using Kaplan-Meier method with log-rank test, Cox proportional hazard regression model, and propensity score matching. Subgroup analyses were conducted by fitting Cox proportional hazard models that include radiation treatment interacting with race, age, facility type, Charlson-Deyo score and metastasis. We built several models with each model containing one interaction term.

Results: A sample of 35177 patients were analyzed. From multivariate statistics for OS, radiation therapy showed a significant association with improved overall survival [HR 0.46, CI [0.43, 0.49], P <0.001]. The effect of radiation on overall survival is different in three patient subgroups (interaction p < 0.001, and they High-Risk group [HR 0.43, CI [0.39-0.47], p <0.001], Node-Positive group [HR 0.59, CI [0.52-0.67], p <0.001], and Metastasis group [HR 0.43, CI [0.39-0.48], p <0.001]). Radioation therapy also improved OS for two subgroups of facility type, Academic / Research Program [HR 0.53, CI [0.48-0.57], p <0.001], Non-Academic/Research Program [HR 0.43, CI [0.40-0.47], p <0.001]. These estimated stratified treatment effects was obtained after controlling for other patient demographics and disease characteristics variables.

Conclusions: This study supports the previous finding that beam radiation has a protective effect on prostate cancer patients. The protective effect is more prominent in High-Risk and Metastasis subpopulation than the Node-Positive group.

Table of Contents

1     Introduction

1.1      Prostate cancer and treatments

1.2      Previous clinical trial

1.3      Study Objective

2     Methods

2.1      Introduction of National Cancer Database

2.2      NCDB prostate cancer data set

2.3      Inclusion and Exclusion

2.4      Statistical Analysis

3     Results

3.1      Description of Study Population

3.2      Association between treatment and each covariate

3.3      Univariate association with overall survival

3.4      Multivariate association with overall survival by treatment group

3.5      Multivariable interaction with treatment by subgroups

3.6      Propensity score matching analysis

4     Discussion

5     Conclusion

6     Bibliography

Table 1. Diagram of Study Population Selection

Table 2. Baseline characteristics for the entire study population and by the study cohorts and the factors predict the utilization of radiation therapy

Table 3. Univariate and Multivariable Cox regression analysis of overall survival

Table 4. Multivariable interaction model for overall survival for the effect of radiation in subgroups

Table 5. The estimated 5-yr and 10-yr survival rate by study cohorts in original and matched sample

Table 6. Univariate and Multivariable cox regression analysis of overall survival in PS matched sample

Table 7. Multivariable interaction model for overall survival for the effect of radiation in subgroups (matched sample)

Figure 1: Kaplan-Meier curves by Radiation Yes vs. No

Figure 2: Kaplan-Meier curves by Radiation Yes vs. No in PS matched sample

Figure 3. PS matching overlap

Figure 4. Covariate balance check before and after PS matching

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