Whether the Proton Beam Radiation Leads to Less Second Malignancies among Localized Prostate Cancer Patients Public

Abstract

Background: The primary radiotherapies for prostate cancer patients include three-dimensional

conformal radiation therapy (3D-CRT), Intensity-modulated radiation therapy (IMRT), Photon beam

radiation therapy (Photon therapy), Brachytherapy, and Proton beam radiation therapy (Proton therapy).

Although these treatment methods can be curative, radiation carcinogenesis arises as a unique major

concern.

Methods and Materials: NCDB prostate PUF cancer cases diagnosed from 2004 to 2016 were queried

for patient with localized disease and treated by radiation as the first course of treatment plan. ANOVA

and chi-square tests were used to assess the univariate association of radiotherapies and all covariates.

Absolute Standardized Difference was used to check the significance of the association. The univariate

logistic regression and multivariate logistic regression methods were used to assess the association of

secondary tumor with all covariates. Subgroup analysis was also performed. The pairwise propensity

score method was used to reduce selection bias through balancing baseline covariates.

Results: Proton therapy resulted in reduced odds of secondary cancers when compared to other radiation

therapies. After applying the propensity score weighting method, selection bias was eliminated (all ASD

below 0.2). Photon/IMRT/3D-CRT resulted in higher odds of secondary cancers when compared with

Proton therapy (OR: 4.31 (95%CI: 4.07-4.56)). In comparing Brachytherapy versus Proton therapy as the

reference group, the odds of secondary tumors were also statistically significant (OR: 3.45 (95%CI:3.21-

3.70)). The association of secondary tumor was modified by the race-ethic groups, the year of diagnosis

groups, and the gleason groups in comparison to Proton vs. Photon/IMRT/3D-CRT and Proton vs.

Brachy. NH-White patients had higher odds ratio with Photon/IMRT/3D-CRT therapy (OR:5.04 (95%CI:

4.73-5.37)) or Brachytherapy (OR:3.95 (95%CI: 3.64-4.28)) comparing with Proton therapy. Patients

from earlier year of diagnosis had higher odds ratio due to longer follow-up. Patients with lower Gleason

score had much higher odds ratio in comparison to Proton vs. Photon/IMRT/3D-CRT (OR:6.64 (95%CI:

6.02-7.34)) and Proton vs. Brachy (OR:5.12 (95%CI: 4.54-5.77)).

Conclusion: Proton therapy had the least risk of developing secondary tumors compared with therapies of

other radiation modalities. The propensity score weighting method could eliminate bias in observation

since our data was well balanced with propensity score adjustment.

Table of Contents

1. Introduction ................................................................................................................................ 1

2. Method ........................................................................................................................................ 3

2.1 Data Source .......................................................................................................................... 3

2.2 Study population .................................................................................................................. 4

2.3 Outcome Measures............................................................................................................... 4

2.4 Study Cohorts ....................................................................................................................... 5

2.5 Study Variables .................................................................................................................... 5

2.6 Statistical Method ................................................................................................................ 6

3. Results ......................................................................................................................................... 8

3.1 Overall patients’ baseline characteristics and differences by study cohorts. (Table 1) . 8

3.2 Association with the rate of the secondary tumor in the original sample. (Figure 1,

Figure 2, Table 2) ....................................................................................................................... 9

3.3 Association with the rate of the secondary tumor in propensity score weighted sample.

(Figure 3, Table 3) .................................................................................................................... 10

4. Discussion ................................................................................................................................. 11

5. Conclusion ................................................................................................................................ 13

6. Reference .................................................................................................................................. 13

7. Figures and Tables ................................................................................................................... 15

About this Master's Thesis

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School	Rollins School of Public Health
Department	Biostatistics
Subfield / Discipline	Biostatistics - MPH & MSPH
Degree	M.P.H.
Submission	Master's Thesis
Language	English
Research Field	Biology, Biostatistics
Mot-clé	Prostate Cancer
Committee Chair / Thesis Advisor	Yuan Liu, Emory University
Committee Members	Zhengjia (Nelson) Chen, University of Illinois at Chicago

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