Nima Aghdam, MD, MS
PV QA 1 - Poster Viewing Q&A 1
Purpose/Objective(s): Stereotactic Body Radiation Therapy (SBRT) has emerged as a convenient, effective, and safe treatment option for favorable risk prostate cancer. A benign Prostate-Specific Antigen (PSA) bounce is a temporary elevation of PSA above prior values. These PSA variations are common following ultra-hypofractionated SBRT (30-40%) and frequently lead to patient anxiety. In this report, we compare our standard PSA surveillance schedule with an alternative longer interval routine to determine its impact on the incidence of benign PSA bounces and timely detection of biochemical failures.
Materials/Methods: Seven hundred and thirty three patients with low (n = 221) and intermediate (n = 512) risk prostate cancer were treated with SBRT to a total dose of 35–37.5 Gy in 5 fractions at a single academic hospital between January 2008 and December of 2017. Patients treated with androgen deprivation therapy were excluded from this study. PSA nadirs, PSA bounces, and biochemical failures were recorded during the first three years of follow up. Any PSA rise of ≥ 0.2 ng/ml with a subsequent return to baseline was recorded as a benign PSA bounce. Any PSA rise of ≥ 2 ng/ml from the nadir without resolution back to baseline was recorded as biochemical failure. The standard follow up schedule “A” involved PSA draws one month after the completion of SBRT, every 3 months for the first year and then every 6 months for the second and third years. The abbreviated follow up schedule “B” was derived from the same data points at 3, 12, 24, 36 months.
Results: Schedule “A” included 4,764 PSA values drawn as compared to 1,955 in Schedule “B” – a reduction of 59%. During years 1, 2, and 3 of follow up, Schedule A identified 167, 93 and 60 benign PSA bounces, respectively. In Schedule “B” PSA bounce identification was reduced to 42, 21, and 25 during first, second, and third year, respectively, - a reduction of 75%, 77% and 58%, respectively relative to Schedule "A". There were no statistically significant differences in the yearly PSA nadirs between the two schedules. Nine biochemical failures were identified during the three-year follow up period. Only one biochemical failure identification would have been delayed six months by utilization of the reduced follow-up schedule.
Conclusion: The ideal PSA surveillance schedule after undergoing SBRT is unknown. A conservative PSA surveillance schedule following prostate SBRT reduces the rate of benign PSA bounces without a significant reduction in the early detection of biochemical failures. The proposed modified early PSA surveillance schedule may reduce patient anxiety and preserve valuable clinical resources.
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