A method to separate the rectum from the prostate during proton beam radiotherapy of prostate cancer patients.
The use of protons for curative treatment of prostate cancer is increasing, either as a single treatment modality or in combination with conventional radiotherapy. The proximity between prostate (target) and rectum (organ at risk) often leads to a compromise between dose to target and organ at risk.


METHODS
The present study describes a method where the distance between prostate and rectum is increased by retraction of the rectum in dorsal direction. Comparative treatment plans with and without retraction of the rectum in the same patients have been studied. Nine patients with biopsy proven, localised adenocarcinoma of the prostate were studied. A cylindrical rod of Perspex was inserted into the rectum. This device allows the rectum to be retracted posteriorly. The patients were given a proton boost of 20 Gy in four fractions of 5 Gy in addition to a conventional photon beam treatment to a dose of 50 Gy in 25 fractions of 2 Gy.


RESULTS
Comparative treatment planning shows that the treatment plan with rectal retraction significantly reduces (p<0.01) the volume of the rectal wall receiving high doses (equal to 70 Gy in 2 Gy fractions) in all patients.


CONCLUSIONS
The proton boost treatment with retraction of rectum during treatment decreases the rectal dose substantially. This is expected to reduce rectal side effects.
Isacsson
Ulf
U
Sections of Oncology and Medical Radiation Physics, Department of Oncology, Radiology and Clinical Immunology, Uppsala University Hospital, Uppsala, Sweden. ulf.isacsson@akademiska.se
Nilsson
Kristina
K
Asplund
Stefan
S
Morhed
Elizabeth
E
Montelius
Anders
A
Turesson
Ingela
I
D000230:Adenocarcinoma / Q000532:radiotherapy*; D000368:Aged; D000369:Aged, 80 and over; D019583:Dose Fractionation, Radiation; D006801:Humans; D008297:Male; D008875:Middle Aged; D017785:Photons / Q000627:therapeutic use; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D061766:Proton Therapy; D011878:Radiotherapy / Q000379:methods; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012007:Rectum / Q000528:radiation effects*; D013525:Surgical Instruments; D011522:Protons
D011522:Protons