A radiobiological study of the schemes with a low number of fractions in high-dose-rate brachytherapy as monotherapy for prostate cancer

High-dose-rate brachytherapy as monotherapy for low- and intermediate-risk prostate cancer: long-term experience of Swedish single-center

Purpose

Until now, most long-term results for brachytherapy only has been published for low-dose-rate (LDR) seeds. Due to radiobiology reasons, high-dose-rate (HDR) mono-brachytherapy is of growing interest. The aim of the study was to report long-term biochemical control rate and toxicities with HDR monotherapy.

Material and methods

This was a retrospective single-institution experience, including 229 men, clinically staged T1c-T2b, Gleason 3 + 3 (prostate specific antigen (PSA) ≤ 15), or Gleason 3 + 4 (PSA ≤ 10), consecutively treated between 2004 and 2012 with HDR brachytherapy alone, using three different fractionation schedules of 92-95 Gy (EQD(2), α/β = 3). Group 4F (n = 19) had a single implant of 9.5 Gy in four fractions over 2 days. Group 3F (n = 107) had three separate implants of 11 Gy over 4 weeks. Group 2F (n = 103) had two implants of 14 Gy over 2 weeks. No adjuvant hormonal therapy was allowed.

Results

For 4F, 3F, and 2F study groups, median follow-up was 10.2, 7.1, and 6.1 years, respectively, and biochemical failure rate was 10.5%, 4.7%, and 14.6%, respectively. Early and late side effects were followed with common terminology criteria version 2.0 and patient-reported questionnaires. There were a temporary acute urethral toxicity increase, 1-2 grades over baseline lower urinary tract symptoms (LUTS), which usually recovered. About 1/3 of the patients had a remaining one grade over baseline LUTS. Severe grade 3-4 toxicity were only found in 3.5% of patients. No rectal toxicity was observed. Erectile dysfunction (ED) was depending on age and erectile function before treatment. In patients without ED before the treatment, we found a complete ED in 21% of men at the last follow-up.

Conclusions

In the present study, HDR mono-brachytherapy was found to be an effective treatment, with mild long-term side effects difficult to differentiate from aging effects. There were no significant differences in PSA regression, PSA failure rate, and toxicity between the different fraction schedules.

Salvage brachytherapy for locally recurrent prostate cancer after single-fraction 19 Gy high-dose-rate brachytherapy: toxicity, prostate-specific antigen kinetics, and cancer control

Purpose

To evaluate toxicity, prostate-specific antigen (PSA) kinetics, and cancer control of high-dose-rate brachytherapy (HDR-BT) as a salvage modality for men with locally recurrent prostate cancer, after primary HDR-BT failure.

Material and methods

Twelve patients with biochemical failure and a local relapse after 19 Gy single-fraction high-dose-rate brachytherapy (HDR-BT 19 Gy) were salvaged using two HDR-BT fractions. Salvage treatment consisted of two HDR-BT applications, one week apart, delivering 12 Gy to the prostate per application (HDR-BT 12 × 2).

Results

Median age and initial PSA prior to rescue treatment were 74 years (range, 65-80) and 5.29 ng/ml (range, 2.37-16.40), respectively. Forty-two percent had a low-risk and 58% presented with intermediate-risk prostate cancer. Median follow-up period was 26 months (range, 10-42). Median time to PSA nadir was 12 months, with a median value of 0.21 ng/ml. Most of the patients (11 of 12) achieved a PSA decline ≥ 90%. Acute grade 2 genitourinary (GU) toxicity occurred in 4 patients (33.3%) and none presented with acute gastrointestinal (GI) toxicity. Two patients (16.7%) suffered from late GU grade 2 toxicity. No grade 3 toxicity were recorded. To date, 2 patients (16.7%) have experienced biochemical failure after salvage treatment.

Conclusions

Salvage HDR-BT 12 × 2 is a feasible and well-tolerated treatment, with acceptable toxicity rates for men with locally recurrent prostate cancer, who failed after HDR-BT with 19 Gy. Moreover, PSA kinetics and cancer control after salvage treatment suggest that this strategy might be efficacious in this clinical setting.