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Prostate-specific antigen bounce after prostate seed implantation for localized prostate cancer: descriptions and
Richard G Stock1, Nelson N Stone, Jamie A Cesaretti
1Department of Radiation Oncology, Mount Sinai School of Medicine, New York, NY 10029, USA. rstock@mssm.edu
Purpose:
To calculate the actuarial risk of developing a prostate-specific antigen (PSA) bounce after prostate brachytherapy alone, using three definitions of bounce mentioned in the literature, and to explore the relationship between disease and treatment variables and the risk of developing a bounce. The impact of PSA bounce on PSA failure was also explored.
Methods And Materials:
A total of 373 patients with T1-T2 prostate cancer underwent radioactive seed implant using 125I (n = 337) or 103Pd (n = 36) without hormonal therapy or external beam RT. All patients had a minimum of 1 year (median 4, maximum 11) of follow-up and at least three follow-up PSA values. PSA bounce was defined by a rise of one or two PSA values with a subsequent fall. Three definitions of bounce were used: definition 1, rise > or = 0.1 ng/mL; definition 2, rise > or = 0.4 ng/mL; and definition 3, rise >35% of previous value.
Results:
The actuarial likelihood of experiencing a PSA bounce at 5 years was 31% for definition 1, 17% for definition 2, and 20% for definition 3. The median time to develop a bounce was 19.5 months for definitions 1 and 2 and 20.5 months for definition 3. Gleason score, initial PSA level, and clinical stage did not predict for bounce using any definition. Using definition 1, younger patients (< or = 65 years) had a bounce rate at 5 years of 38% vs. 24% for older patients (p = 0.009). 125I patients receiving an implant dose of < or = 160 Gy had a bounce rate (definition 1) at 5 years of 24% vs. 38% for those receiving a dose delivered to 90% of the gland on the 1 month postimplant dose-volume histogram (D90) >160 Gy (p = 0.04). Using definition 2, prostate volume significantly affected the incidence of bounce. Patients with larger glands (>35 cm(3)) were more likely to experience a bounce (23% at 5 years) than those with smaller glands (< or = 35 cm(3)) who had a bounce rate of 11% at 5 years (p = 0.01). In a multivariate analysis of factors predicting for PSA failure, PSA bounce was not found to be significant.
Conclusion:
PSA bounce is a common phenomenon after prostate brachytherapy and occurs at a rate of 17-31%, depending on the definition used. It is more common in younger patients, those receiving higher implant doses, and those with larger glands. PSA bounce does not predict for future PSA failure.