Room: Exhibit Hall
Purpose: A rectal retractor (RR) is a rectal displacement device which pushes the lateral and posterior rectal wall away from high dose areas. We investigated the role of RR in reducing the dose to the rectum, during dose escalated prostate radiotherapy.
Methods: In the pilot study, twelve patients with localized prostate cancer enrolled and used RR in the first 25 out of 40 fractions. One week prior to CT planning, three fiducial gold markers were implanted into the prostate gland. All patients underwent two CT planning without and with RR (Figure 1). One radiation oncologist delineated the clinical target volume (CTV) and organ at risks. The planning target volume (PTV) was defined with an isotropic margin of 5 mm around the CTV by a physicist. Patients were treated with image-guided three-dimensional conformal radiotherapy to a total dose of 80 Gy in 40 fractions. An electronic portal imaging device was used daily, to correct the position of the fiducial gold markers. Dose volume histograms (DVHs) were generated. Rectum DVH parameters in plan without and with RR compared to the paired-t test.
Results: The PTV was comparable in plan without and with RR (p= 0.531). A significant difference in the rectal volumes was found between without and with RR (p= <0.001). The average (Â±SD) volume of the rectum without and with RR was 63.5 (Â±15.7) cc and 83.7 (Â±16.3) cc, respectively. The DVH parameters for the rectum in plan without and with RR are given in Table 1. The use of RR significantly reduced the dosimetric parameters of the rectum.
Conclusion: Utilizing a RR resulted in a decrease in the dose administered to the rectum, which can reduce acute and late rectal toxicities. The role of RR in the full course of moderate hypofractionated prostate intensity radiotherapy will now be investigated.