부산대학교 도서관

Purpose: To evaluate patient's tolerability of the initial dose levels in a dose-escalation study for localized prostate cancer, using linear accelerator-delivered SBRT. Patients and Methods: Patients included those with Gleason score < 7 with prostate-specific antigen (PSA) ≤ 10, Gleason score 7 with PSA ≤ 15, ≤ T2b, prostate size ≤ 60 cm3, and (AUA) score ≤ 15. Patients were enrolled in a prospective single-institution, institutional review board-approved study. Pretreatment preparation required intraprostatic fiducial placement and MRI acquired and fused with the simulation CT of each patient. Starting at 40 Gy in 5 fractions (delivered twice a week), the dose was safely escalated to 45 Gy in 5 fractions. All treatments were prescribed to the 90% isodose surface and were given with a dedicated linac-integrated stereotactic delivery system . An X-ray verification accuracy threshold of 1.0 mm and intra-fraction verification was performed every 60 seconds during treatment to ensure accurate targeting without treatment interruption. Dose-limiting toxicity (DLT) was defined as G 3 or worse GI/GU toxicity by CTCAEv3. Patients completed Expanded Prostate Cancer Index Composite (EPIC) prostate quality of life questionnaires starting at 3 weeks post treatment and every three-months thereafter. Results: 12 patients completed the initial dose level (40Gy in 5 fractions over 2 weeks) and 10 were treated in the second dose level of 45 Gy in 5 fractions biweekly. Mean baseline AUA score was 5.5. The worst GU toxicity reported during treatments was G 1 in 67% in both dose levels, and G 2 in 42% and 50% respectively; without a single G 3 toxicity. 2 patients experienced G 1 rectal bleeding. After a median follow-up of 12 months (range 11-20 month) for patients in dose level one and 7 months in dose level two (range, 3 -12 months) no delayed GI toxicity was reported. 6 patients reported G1 erectile dysfunction with a decreased libido in 3. Transient G 1 increased urinary frequency was noticed in 4 patients, two in each level. Rectal quality-of-life scores remained at the baseline levels at both dose levels. In all patients, PSA control is 100% by the nadir + 2 ng/mL failure definition. Conclusion: Prostate SBRT using our approach and with dose level of 45 Gy in 5 fractions is well tolerated. Longer follow up is warranted to assess long-term toxicity and tumor control rates. The results of this study allow for treating patients to 50 Gy in five fractions. Disclosure: No significant relationships. [ABSTRACT FROM AUTHOR]