Rectal toxicity after intensity modulated radiotherapy for prostate cancer: Which rectal dose volume constraints should we use? - Abstract

BACKGROUND: To define rectal dose volume constraints (DVC) to prevent ⩾grade2 late rectal toxicity (LRT) after intensity modulated radiotherapy (IMRT) for prostate cancer (PC).

MATERIAL AND METHODS: Six hundred thirty-seven PC patients were treated with primary (prostate median dose: 78Gy) or postoperative (prostatic bed median dose: 74Gy (adjuvant)-76Gy (salvage)) IMRTwhile restricting the rectal dose to 76Gy, 72Gy and 74Gy respectively. The impact of patient characteristics and rectal volume parameters on ⩾grade2 LRT was determined. DVC were defined to estimate the 5% and 10% risk of developing ⩾grade2 LRT.

RESULTS: The 5-year probability of being free from ⩾grade2 LRT, non-rectal blood loss and persisting symptoms is 88.8% (95% CI: 85.8-91.1%), 93.4% (95% CI: 91.0-95.1%) and 94.3% (95% CI: 92.0-95.9%) respectively. There was no correlation with patient characteristics. All volume parameters, except rectal volume receiving ⩾70Gy (R70), were significantly correlated with ⩾grade2 LRT. To avoid 10% and 5% risk of ⩾grade2 LRT following DVC were derived: R40, R50, R60 and R65 < 64-35%, 52-22%, 38-14% and 5% respectively.

CONCLUSION: Applying existing rectal volume constraints resulted in a 5-year estimated risk of developing late ⩾grade2 LRT of 11.2%. New rectal DVC for primary and postoperative IMRT planning of PC patients are proposed. A prospective evaluation is needed.

Written by:
Fonteyne V, Ost P, Vanpachtenbeke F, Colman R, Sadeghi S, Villeirs G, Decaestecker K, De Meerleer G.   Are you the author?
Ghent University Hospital, Department of Radiation Oncology and Experimental Cancer Research, Belgium; Ghent University, Biostatistics Unit, Department of Public Health, Faculty of Medicine and Health Sciences, Belgium; Ghent University Hospital, Department of Radiology, Belgium; Ghent University Hospital, Department of Urology, Belgium.  

Reference: Radiother Oncol. 2014 Dec;113(3):398-403.
doi: 10.1016/j.radonc.2014.10.014

PubMed Abstract
PMID: 25441610 Prostate Cancer Section