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.
OBJECTIVE
To investigate whether a large rectum filling visible on the planning CT scan was associated with a decrease in freedom from any failure (FFF) and freedom from clinical failure (FFCF) for prostate cancer patients.


METHODS
Patients from the Dutch trial (78 Gy vs. 68 Gy) with available acute toxicity data were analyzed (n = 549). A 10-mm margin was applied for the first 68 Gy and 0-5 mm for the 10-Gy boost. The dose in the seminal vesicles (SVs) was prescribed within four treatment groups according to the estimated risk of SV involvement. Two potential risk factors (RFs) for a geometric miss were defined: (1) an anorectal volume > or = 90 cm(3) and > or = 25% of treatment-time diarrhea (RF1); and (2) the mean cross-sectional area of the anorectum (RF2). We tested whether these were significant predictors for FFF and FFCF within each treatment group.


RESULTS
Significant results were observed only for patients with a risk of SV involvement > 25% (dose of 68-78 Gy to the SVs, n = 349). We found a decrease in FFF (p = 0.001) and FFCF (p = 0.01) for the 87 patients with RF1 (for RF2, p = 0.02 and p = 0.01, respectively). The estimated decrease in the FFCF rate at 5 years was 15%.


CONCLUSIONS
Tumor control was significantly decreased in patients with a risk of SV involvement > 25% and at risk of geometric miss. Current image guidance techniques offer several solutions to geometrically optimize the treatment. Additional research is needed to evaluate whether geometric misses can be prevented using these techniques.
Heemsbergen
Wilma D
WD
Department of Radiation Oncology, The Netherlands Cancer Institute--Antoni van Leeuwenhoek Hospital, Amsterdam, The Netherlands. w.heemsbergen@nki.nl
Hoogeman
Mischa S
MS
Witte
Marnix G
MG
Peeters
Stéphanie T H
ST
Incrocci
Luca
L
Lebesque
Joos V
JV
D000368:Aged; D016001:Confidence Intervals; D003967:Diarrhea / Q000150:complications* / Q000453:epidemiology; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D011471:Prostatic Neoplasms / Q000097:blood / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal; D012007:Rectum / Q000000981:diagnostic imaging* / Q000473:pathology; D012307:Risk Factors; D012669:Seminal Vesicles / Q000473:pathology / Q000528:radiation effects; D014057:Tomography, X-Ray Computed