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Do differences in target volume definition in prostate cancer lead to clinically relevant differences in normal
Jacqueline E Livsey1, James P Wylie, Ric Swindell
1Department of Clinical Oncology, Manchester, United Kingdom. jaclivsey@hotmail.com
International Journal of Radiation Oncology, Biology, Physics
|November 3, 2004
Summary
Interclinician variability in prostate cancer target volume definition did not lead to significant clinical differences in rectal or bladder toxicity. Despite variations in outlining, the impact on normal tissue complication probabilities was minimal, suggesting less clinical relevance than previously assumed.
Area of Science:
- Radiation Oncology
- Medical Imaging
- Clinical Oncology
Background:
- Quantified differences in target volume definition among clinicians are well-documented in prostate cancer radiotherapy.
- However, the clinical impact and sequelae of these interclinician variations remain less understood.
Purpose of the Study:
- To assess the clinical relevance and consequences of interclinician variability in defining target volumes for prostate cancer.
- To evaluate the impact of these variations on normal tissue complication probabilities (NTCPs) for the bladder and rectum.
Main Methods:
- Five radiation oncologists delineated clinical target volumes (CTVs) and planning target volumes (PTVs) for five early-stage prostate cancer patients.
- Dose-volume histograms were generated, and NTCPs for the bladder and rectum were estimated using the Pinnacle planning system.
Main Results:
- Statistically significant differences were observed in CTV and PTV delineations among clinicians (p < 0.0005), particularly at the prostatic apex and seminal vesicles.
- No significant differences were found in rectal V(x) or most bladder V(x) parameters, except for bladder V(90) (p = 0.015).
- Estimates of bladder (p = 0.1) and rectal (p = 0.09) NTCPs showed no statistically significant interclinician differences.
Conclusions:
- While interclinician variability in prostate cancer target volume definition exists, it did not translate into clinically significant differences in irradiated rectal and bladder volumes or NTCPs.
- The findings suggest that variations in outlining may have less clinical impact than previously thought, potentially due to the critical areas of overlap and the relative impact of different regions on toxicity.