PV QA 1 - Poster Viewing Q&A 1
Purpose/Objective(s): To evaluate the efficacy of nutrition education on changes in daily rectal volume and dose during intensity-modulated radiotherapy (IMRT) treatment in patients with prostate cancer.
Materials/Methods: We retrospectively evaluated changes in rectal volume in patients with prostate cancer who received IMRT as a radical treatment between January 2014 and December 2017 at our hospital. Thirty consecutive patients who underwent a nutrition education program (educated group) and 30 patients who did not undergo the program (non-educated group) were included. The nutrition education program was conducted (1) to ask patients about their dietary and bowel habits, (2) to teach the importance of avoiding constipation and rectal gas filling, (3) to teach habits that should be promoted (for example: consuming a high-fiber diet, drinking 1.5–2 liters of water per day, and engaging in regular exercise), and (4) to teach dietary habits that should be avoided (for example: overconsumption of meat and fast eating). Daily pre-treatment kilovoltage cone beam computed tomography (CBCT) images were acquired for all patients. The treatment-planning CT and 12 CBCT images were used for each patient. The rectum was delineated on the planning CT (planning-rectum) and 12 CBCT (CBCT-rectum) images for each patient. The rectal and overlap volumes between the PTV and rectum were calculated as relative changes between the planning CT and CBCT images (rRectal-V and rOverlap-V, respectively). The changes in relative rectal volumes receiving 40 Gy, 60 Gy, and 70 Gy were defined as rV40, rV60, and rV70, respectively. The volumes of the CBCT-rectum and planning-rectum were compared using Fisher’s exact test, and the rRectal-V, rOverlap-V, rV40, rV60, and rV70 were compared using the Mann–Whitney U test.
Results: Seven hundred and twenty CBCT images were available for analysis. In the non-educated group, 59.4% of the CBCT-rectums were larger than the planning-rectums, whereas in the educated group, 45.3% of the CBCT-rectums were larger than the planning-rectums (P < 0.001). The median values of rRectum-V and rOverlap-V were significantly lower (97.1% and 102.5%, respectively) in the educated group than those in the non-educated group (103.5% and 131.1%, respectively) (all P < 0.001). The median values of rV40, rV60, and rV70 were significantly lower (97.1%, 98.3%, and 103.6%, respectively) in the educated group than those in the non-educated group (108.4%, 115.2%, and 122.5%, respectively) (all P < 0.001).
Conclusion: A nutrition education program decreased daily variations in rectal volume and irradiated dose to the rectum. As a result, the reproducibility of the treatment planning increased. This easy and noninvasive method could reduce late rectal toxicities at low costs.
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