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Published on: February 6, 2019
Predicting genitourinary toxicity in three-dimensional conformal radiotherapy for localized prostate cancer: A
Paolo Bagalà1, Gianluca Ingrosso1, Maria Daniela Falco1
1Department of Diagnostic Imaging, Molecular Imaging, Interventional Radiology and Radiotherapy, University of Rome Tor Vergata, Viale Oxford 81, 00133 Rome, Italy.
Purpose:
In prostate cancer radiotherapy, the relationship between genitourinary (GU) toxicity and clinical-dosimetric parameters is debated. We report our analysis of the parameters associated with GU toxicity.
Materials And Methods:
Eighty-six consecutive patients treated with conformal radiotherapy for localized prostate cancer were retrospectively analyzed; the bladder was delineated both as "whole bladder" (WB: Defined in its entirety as a solid organ) and "inferior bladder" (IB: Corresponding to the distal part of the bladder). GU toxicity and dose-volume parameters were correlated using the point biserial correlation coefficient. The normal tissue complication probability (NTCP) cut-off volume model was fitted to toxicity data; univariate analysis between GU toxicity and clinical parameters was done.
Results:
Acute GU toxicity was correlated to doses higher than 80 Gy (P < 0.05) while late GU was correlated to doses higher than 77 Gy for WB and from 77.5 Gy for IB. The NTCP cut-off volume model identified for both WB and IB a bladder volume of 6 cc receiving a dose ≥77 Gy corresponding to a 50% probability of GU toxicity. At univariate analysis, acute GU toxicity was correlated with smoke (P < 0.001).
Conclusion:
Bladder maximal doses quantified as hotspots show a correlation to GU toxicity.
