ESTRO 36 Abstract Book

S516 ESTRO 36 _______________________________________________________________________________________________

Conclusion Our study shows an average systematic 16% smaller prostate volume on TRUS compared to CT. This differs from the 30 to 50% smaller volumes on TRUS reported in the literature. This discrepancy is probably due to the presence of catheters implanted under TRUS guidance in CT based planning which means that catheters are inserted under TRUS guidance in both planning modalities. These catheters act as fiducial markers to delimit the prostate capsule transversely on CT. The residual 16% volume variation is largely due to the uncertainty in identifying the prostate apex. A 2.8 mm isotropic dosimetric margin should be used in order to treat comparable volumes in TRUS compared to CT based planning. PO-0931 Clinical outcome and quality of life after MRI- guided HDR boost for prostate cancer. F. Lakosi 1 , A. Miovecz 1 , G. Antal 1 , J. Pall 2 , D. Nagy 3 , M. Csima 4 , J. Hadjiev 1 , I. Rep a 1 , G. Toller 1 1 Kaposvar University, Radiotherapy, Kaposva r, Hungary 2 Csolnoky Ferenc Hospital, Radiotherapy, Veszprem, Hungary 3 Kaposi Mor Teaching Hospital, Urology, Kaposvar, Hungary 4 Kaposvar University, Faculty of Pedagogy, Kaposvar, Hungary Purpose or Objective To analyze 5-year clinical outcome and quality of life (QoL) after MR-guided high-dose-rate brachytherapy (HDR-BT) combined with 3D conformal external beam Fifty-two patients with intermediate (IR) (n=22) to high- risk (HR) (n=30, 18 T3 diseases) localized prostate cancer were treated with 46-60 Gy of 3D EBRT preceded and/or followed by a single dose of 8-10 Gy MR-guided HDR-BT. Template reconstruction, trajectory planning, image guidance, contouring and treatment planning were exclusively based on MR images. Ninety-six percent of the patients received androgen deprivation. Biochemical relapse–free survival (bRFS, Phoenix definition), local relapse-free survival (LRFS), distant metastasis-free survival (DMFS), cancer-specific survival (CCS) and overall survival (OS) were analyzed actuarially. Morbidity were scored using CTCAEv4.0, while patients self-reported urinary and bowel QoL was measured with the Expanded Prostate Cancer Index Composite (EPIC) instrument and International Prostate Symptom Score (IPSS) at baseline and at regular intervals up to 6 years. Results Median follow-up time was 73 (range:13-103) months. The crude/5-year actuarial rates of bRFS, LRFS, DMFS, CSS and OS were 94/97.4 %, 98/100 %, 96/97 %, 100/100 % and 92/91 %, respectively. Two distant failures occurred in HR group, while one local recurrence in IR group. The main urinary toxicity was dysuria, which were Gr. 2 in 24/52 cases, including 9 patients with alfa blocker use at baseline. There were 3 urinary strictures including one Gr. 3 event. Late GI morbidity was mild, representing Gr. 1 diarrhea (10/51), Gr. 1 urgency (9/51), Gr. 2 proctitis (1/52) and Gr. 2 fecal incontinence (1/52), respectively. A significant decline in urinary domain was observed within the first 3 months, which mostly recovered by 6 months, thereafter declined progressively (p>0.05) and remained stable from 4th years follow up (p>0.05) (Figure). A similar trend was seen for bowel QoL, where a significant decline occured within the first 3 months that subsequently returned to nearly baseline level within 6 months, however, in contrast to urinary functions remained stable over time (p>0.05). The evolution of IPPS scores showed the same pattern as EPIC urinary scores. radiotherapy (3D-EBRT). Material and Methods

Conclusion Five-year clinical outcome of MR-guided HDR-BT boost is encouraging, providing excellent disease control and lack of serious late side effects. A slight decline in long-term urinary QoL was observed. PO-0932 Prostate-specific Antigen bounce in patients treated with 125I prostate brachytherapy: Keep calm A. Pires 1 , D. Moreira 1 , C. Castro 1 , A. Oliveira 1 , J. Oliveira 2 , L. Trigo 3 1 Instituto Português de Oncologia do Porto Francisco Gentil- EPE, Radioncology, Porto, Portugal 2 Instituto Português de Oncologia do Porto Francisco Gentil- EPE, Urology, Porto, Portugal 3 Instituto Português de Oncologia do Porto Francisco Gentil- EPE, Brachytherapy, Porto, Portugal Purpose or Objective Permanent low-dose-rate brachytherapy (BT) with 125 I is an established curative modality for the treatment of localized prostate cancer. After treatment, prostate- specific antigen (PSA) level may fluctuate and temporarily increase without a clear reason. This phenomenon is called “PSA bounce” (PSAb) and often causes anxiety in patient and physician. Our aim was to analyse the kinetics of PSA in our patients and the association between PSA bounce and the long term disease outcome after prostate BT with 125 I. Material and Methods We analysed 134 patients treated with 125 I implantation monotherapy between 2004 and 2006 in a single institution. All patients had tumour stage T1-T2cN0M0, Gleason score ≤ 7 and follow-up time was ≥ 9 years. Patients who received neo-adjuvant hormone therapy were excluded. PSAb was defined as a rise beyound 0.2 ng/ml the initial PSA nadir with a subsequent decline to or below the initial nadir without treatment. Biochemical failure (BF) was determined using the Phoenix definition (nadir +2 ng/mL). Associations between PSAb and the various pre and post-treatment factors were assessed with logistic regression analysis, the association between a PSAb and BF was examined with the log-rank test and the Mann-Whitney U test was applied to test for difference in the time to a PSA rise between PSAb and BF patients. Results PSAb occurred in 53 (39,8%) patients with a median time to bounce of 18,8 months. Only 7 (13,2%) patients with PSAb developed BF, in contrast to 12 (15%) patients without previous bounce (p = 0,084). Among the pre and post-treatment factors, only younger age predicted a PSAb on a multivariate analysis (p = 0.049). PSA levels during the bounce reached levels as high as 8,85 ng/mL in this cohort. BF occurred in 19 patients (14,4%). The 9-year overall survival rate was 83,6%, the 9-year disease-specific survival was 95,8% and the rate of survival at 9-year freedom from BF was higher than 90%. Conclusion PSAb is a common finding in our population and is associated with a lower rate of subsequent BF. Patients should be advised for the eventual PSAb after permanent 125 I prostate BT. Those who experience a PSAb are more likely to be younger. The physicians involved in patients follow-up after prostate BT should also be aware