Early observed transient prostate-specific antigen elevations on a pilot study of external beam radiation therapy and fractionated MRI guided High Dose Rate brachytherapy boost

Abstract

Purpose: To report early observation of transient PSA elevations on this pilot study of external beam radiation therapy and magnetic resonance imaging (MRI) guided high dose rate (HDR) brachytherapy boost. Materials and methods:Eleven patients with intermediate-risk and high-risk localized prostate cancer received MRI guided HDR brachytherapy (10.5 Gy each fraction) before and after a course of external beam radiotherapy (46 Gy). Two patients continued on hormones during follow-up and were censored for this analysis. Four patients discontinued hormone therapy after RT. Five patients did not receive hormones. PSA bounce is defined as a rise in PSA values with a subsequent fall below the nadir value or to below 20% of the maximum PSA level. Six previously published definitions of biochemical failure to distinguish true failure from were tested: definition 1, rise >0.2 ng/mL; definition 2, rise >0.4 ng/mL; definition 3, rise >35% of previous value; definition 4, ASTRO defined guidelines, definition 5 nadir + 2 ng/ml, and definition 6, nadir + 3 ng/ml.Results: Median follow-up was 24 months (range 18-36 mo). During follow-up, the incidence of transient PSA elevation was: 55% for definition 1, 44% for definition 2, 55% for definition 3, 33% for definition 4, 11% for definition 5, and 11% for definition 6. Conclusion:We observed a substantial incidence of transient elevations in PSA following combined external beam radiation and HDR brachytherapy for prostate cancer. Such elevations seem to be self-limited and should not trigger initiation of salvage therapies. No definition of failure was completely predictive.

PSA Bounce and Biochemical Failure After Brachytherapy for Prostate Cancer: A Study of 820 Patients With a Minimum of 3 Years of Follow-Up

“…Several definitions have previously used: an increase of $0.1 ng/mL (11), $0.2 ng/mL (12,13), 0.4 ng/mL (14), or 0.5 ng/mL (15) or simply an increase of any magnitude (16). It has also been defined as an elevation in PSA between $15% and 35% above the nadir value (14,17,18). Pruthi (19) emphasized that the minor fluctuations in PSA are not unique to patients undergoing brachytherapy but can simply be explained by the normal, expected, and already welldescribed variability of serum PSA determinations.…”

Describing Prostate Cancer Dynamics: Second Look at PSA- Doubling Time and PSA-Specific Growth Rate

“…An important caveat is expressed by Newling's review [33] of the subject which concluded that though dynamic changes in the PSA such as PSA-DT are commonly used in clinical trials of new drug therapies, PSA-DT might be affected by other factors including assay variations and false elevations of serum PSA caused by irritation of bladder catheters, prostatitis and cystitis. A substantial incidence of transient elevations of PSA (55%) was reported following combined external beam radiation and brachytherapy for prostate cancer [34]. These complicating issues should always be considered before PSA-DT is used to modify therapy.…”