Long term outcome and side effects in patients receiving low-dose I125 brachytherapy: a retrospective analysis

Abstract

Objectives: To retrospectively evaluate the disease free survival (DFS),disease specific survival (DSS),overall survival (OS) and side effects in patients who received low-dose rate (LDR) brachytherapy with I125 stranded seeds.

Materials and methods: Between july 2003 and august 2012, 274 patients with organ confined prostate cancer were treated with permanent I125 brachytherapy. The median follow-up, age and pretreatment prostate specific antigen (iPSA) was 84 months (12-120), 67 years (50-83) and 7.8 ng/mL (1.14-38), respectively. Median Gleason score was 6 (3-9). 219 patients (80%) had stage cT1c, 42 patients (15.3%) had stage cT2a, 3 (1.1%) had stage cT2b and 3 (1.1%) had stage cT2c. The median D90 was 154.3 Gy (102.7-190.2).

Results: DSS was 98.5%.OS was 93.5%. 13 patients (4.7%) developed systemic disease, 7 patients (2.55%) had local progression. In 139 low risk patients, the 5 year biochemical freedom from failure rate (BFFF) was 85% and 9 patients (6.4%) developed clinical progression. In the intermediate risk group, the 5 year BFFF rate was 70% and 5 patients (7.1%) developed clinical progression. Median nPSA in patients with biochemical relapse was 1.58 ng/mL (0.21 - 10.46), median nPSA in patients in remission was 0.51 ng/mL (0.01 - 8.5). Patients attaining a low PSA nadir had a significant higher BFFF (p<0.05). Median D90 in patients with biochemical relapse was 87.2 Gy (51 - 143,1). Patients receiving a high D90 had a significant higher BFFF (p<0.05).

Conclusion: In a well selected patient population, LDR brachytherapy offers excelente outcomes. Reaching a low PSA nadir and attaining high D90 values are significant predictors for a higher DFS.

Keywords: Brachytherapy; Prostate-Specific Antigen; Prostatic Neoplasms.

Figure 1. % relapse compared to nPSA level. Patients attaining a low PSA nadir have a significantly improved BFFF. When we compare the 5 year biochemical free survival in patients based on the PSA nadir, there is an almost linear correlation between the nadir and the relapse rate.

Figure 2. % patients reaching nPSA at specific intervals. 50% of the patients reached the nadir 1 year after brachytherapy, 82% of the patients reached the PSA nadir 5 years postoperatively.

Figure 3. Mean nPSA values in different patients measured at specific time interval. Reaching the PSA nadir fast does not necessarily mean that the treatment is more efficient. Patients with a slowly declining PSA tended to reach a lower PSA nadir.

Figure 4. Left: Image of intra-operative planning on transrectal ultrasound. The colored lines mark the different areas where the radiation dose is similar. Urethra and rectum are marked to keep the radiation dose as low as possible in these regions. Right: 3D reconstruction of the seeds after implantation.

Figure 5. RTOG score, used to evaluate late urinary toxicity (>3 months). Only a minority of the patients had urinary complaints. Dysuria and frequency (grade 2) were the most common urinary side-effects of the treatment. Hematuria was only present in 1.4% of the patients.

Figure 6. RTOG score, used to evaluate late rectal toxicity (> 3 months). In St Lucas, only 2.8% of the patients had rectal toxicity, none higher than grade 2.