ESTRO 36 Abstract Book

S514 ESTRO 36 _______________________________________________________________________________________________

24.3% cases. Only in 24.3% observations D90 was above 100% (table 1). In addition, in 18% of these cases D10 for urethra was between 116% and 189%.

Figure 1: Difference in D90 (%) between plugged (blue) and plug-free (pink) needles in each sector. Conclusion Our study suggests that plug-free needles have the potential to improve implant quality via better spatial dose distribution within the prostate using fewer numbers of needles and reduced seed loss. Further, it provides added freedom to use any number of special loaded strands without increasing needle numbers. PO-0928 Androgen deprivation therapy influences PSA bounce rate after brachytherapy W. Burchardt 1 , M. Kanikowski 1 , J. Skowronek 1 1 Greater Poland Cancer Centre, Brachytherapy, Poznan, Poland Purpose or Objective To evaluate predictive clinical and dosimetric factor for PSA bounce (PB) after HDR and LDR brachytherapy with or without androgen deprivation therapy (ADT). PB can imitate biochemical failure and causes introduction of unnecessary diagnostics and patients’ treatment. Material and Methods We analysed data of 101 patients (age 50-81 years) with clinical localized prostate cancer (T1-T2cN0) treated with brachytherapy from June 2008 to December 2010 at Greater Poland Cancer Centre in Poznan, Poland. Neoadjuvant or adjuvant androgen deprivation therapy was applied in 33 cases. All patients underwent LDR (LDR n=41) or HDR (HDR n=53) brachytherapy with curative intent. The total doses (TD) for LDR was 145 Gy and for HDR brachytherapy 3 x 10,5 - 15 Gy. Results A total of 94 patients were followed up at our Cancer Centre. Median follow-up was 3,0 years. Average initial PSA (iPSA) value was 7,8 ng/ml +/-3,1 (SD). In the follow up the median PSA nadir 0,1 ng/ml was achieved after median 21 months. In 58 cases PSA decreased gradually without any event. In 23 cases PB was observed using 0,2 ng/ml definition. In 10 cases (11%) biochemical failure (BF) was diagnosed using nadir + 2 ng/ml definition. In 24% of patients PB was observed. Patients treated with ADT experienced fewer PB than hormone naïve patients (90 % vs. 62%, p=0,016). Patients with PB achieved later and higher PSA nadir (time to nadir 30 vs. 18 months and PSA nadir 0,3 vs. 0,1 ng/ml). Clinical stage, Gleason scale, iPSA and risk groups were not different between PB and No PB groups. Conclusion Patients after brachytherapy for low and intermediate risk prostate cancer had PB in 24 % of cases. ADT decreased the PB rate after brachytherapy what could have protected the patients from unnecessary interventions. Patients with PB had later and higher level of PSA nadir. Other clinical and dosimetric factors were not predictive for PB.

Conclusion post-implantation correction of prostate, urethra, bladder and rectum volumes with subsequent postimplantation planning of dose distribution must be considered as obligatory part of safe and accurate prostate brachytherapy. PO-0927 Plug-free needles provide dosimetric advantages over plugged needles in I-125 prostate brachytherapy A.B. Mohamed Yoosuf 1 , L. Sarri 1 , M. Byrne 1 , G. Workman 1 , D. Mitchell 2 , S. Jain 2 1 Northern Ireland Cancer Centre, Radiotherapy Medical Physics Service, Belfast, United Kingdom 2 Northern Ireland Cancer Centre, Department of Clinical Oncology, Belfast, United Kingdom Purpose or Objective To compare the dosimetric outcome of plugged and plug- free implant needles in permanent prostate brachytherapy (PPB) using global and multi-sector post implant dosimetric analysis. Material and Methods 70 consecutive men treated with I-125 PPB using either plugged (group 1, n=35) or plug-free (Group 2, n=35) had their post implant (CT) dosimetry compared. For global analysis, dosimetric quality indicators evaluated between two groups included: prostate volume (CT), number of needles per unit volume, the minimum dose delivered to 90% of prostate volume (D 90 ) and dose to 0.1 cm 3 of the rectum (D 0.1cc ). Twelve sectors of the post-implant CT was analysed for each case by dividing the prostate base, mid gland and apex into four sectors each and D 90 was compared for both groups. Results The mean prostate volume for Group 2 (40.38 cc ± 8.0 cc) was significantly larger (p < 0.05) than Group 1 (36.45 cc ± 8.5 cc) but fewer needles were required per unit volume (Group 2 - 0.59 ± 0.12 cm -3 vs Group 1 - 0.72 ± 0.18 cm -3 ; p < 0.001). Global dosimetry was similar for both groups however seed loss was significantly reduced in Group 2 (p < 0.05). Sector analysis, for Group 2, indicated increased D 90 in the posterior mid-gland and apex regions (p < 0.05) and a trend towards increased dose in the base sector as shown in Figure 1. The mean rectal D 0.1cc was higher in Group 2 than Group 1 (124.73% ± 12.2% vs 122.54% ± 10.3%; p = 0.4) which reflected the increased dose in the posterior mid-gland. However, these remained within recommended tolerances.