Prostate radiotherapyImpact of planning target volume margins and rectal distention on biochemical failure in image-guided radiotherapy of prostate cancer
Section snippets
Patient characteristics
We retrospectively evaluated a total institutional cohort of 50 men with cT1–3N0M0 prostate cancer who were treated consecutively between February 2002 and October 2009 with conformal arc RT (n = 42) or intensity-modulated RT (IMRT) (n = 8) on the Novalis system with daily IGRT by 3 fiducial gold markers, the latter implanted transrectal with ultrasound guidance. Mean age was 64 years (range, 52–79). Twenty of these patients in addition received concurrent androgen deprivation therapy (ADT). The
Results
The overall 5-year FFBF was 83% (95% CI 67–92). The 5-year FFBF was 76% (95% CI 52–90) for the high- to very-high risk group compared to 90% (95% CI 63–97) for the intermediate- to low-risk group (p = 0.10). Patients in whom a PTV margin of 6 mm was applied (n = 25) displayed a statistically significant better FFBF compared to those (n = 25) with the tighter PTV margin of 3–5–4 mm (5-year FFBF 96% vs 74%, p = 0.04) (Fig. 1A). Of notice, the average CSA did not differ significantly between the group of
Discussion
The current retrospective study provides evidence of improved outcome after prostate IGRT with the use of adequate safety margins by demonstrating a 22% absolute gain in 5-year FFBF (96% vs 74%) with a PTV margin of 6, 6 and 6 mm in the LL, AP and CC directions as compared to 3, 5 and 4 mm. The isotropic 6 mm margin was applied for our marker positioning procedure since January 2008 based on data concerning intrafraction prostate motion and on the margin recipe by Van Herk et al. [6], [15], [16],
Conclusion
The combination of tight PTV margins and a distended rectum at time of the planning CT affected dramatically FFBF in prostate cancer patients undergoing daily IGRT by implanted markers. The current retrospective study illustrated a significant improvement in FFBF with the use of adequate PTV margins and emphasizes on the importance of avoiding rectal distention at time of the planning CT.
Conflict of interest
None to declare.
Acknowledgement
This research was not funded by grants.
References (25)
- et al.
Increased risk of biochemical and local failure in patients with distended rectum on the planning CT for prostate cancer radiotherapy
Int J Radiat Oncol Biol Phys
(2005) - et al.
Conformal arc radiotherapy for prostate cancer: increased biochemical failure in patients with distended rectum on the planning computed tomogram despite image guidance by implanted markers
Int J Radiat Oncol Biol Phys
(2009) - et al.
Increased risk of biochemical and clinical failure for prostate patients with a large rectum at radiotherapy planning: results from the Dutch trial of 68 Gy versus 78 Gy
Int J Radiat Oncol Biol Phys
(2007) - et al.
Impact of image guidance on outcomes after external beam radiotherapy for localized prostate cancer
Int J Radiat Oncol Biol Phys
(2008) - et al.
Evaluation of image-guided strategies in the treatment of localized prostate cancer
Int J Radiat Oncol Biol Phys
(2008) - et al.
The probability of correct target dosage: dose-population histograms for deriving treatment margins in radiotherapy
Int J Radiat Oncol Biol Phys
(2000) - et al.
Phase II study of a four-week hypofractionated external beam radiotherapy regimen for prostate cancer: report on acute toxicity
Radiother Oncol
(2006) - et al.
Correlation of pre-therapy prostate cancer characteristics with histologic findings from pelvic lymphadenectomy specimens
Int J Radiat Oncol Biol Phys
(1996) - et al.
Correlation of pre-therapy prostate cancer characteristics with seminal vesicle invasion in radical prostatectomy specimens
Int J Radiat Oncol Biol Phys
(1996) - et al.
Setup accuracy of stereoscopic X-ray positioning with automated correction for rotational errors in patients treated with conformal arc radiotherapy for prostate cancer
Radiother Oncol
(2006)