Abstract Book

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ESTRO 37

reported biochemical control rates of 91% for intermediate-risk and 77% for high-risk patients at 8 years. Late Grade 3 GU and GI toxicity rates were 1% and 2% at 8 years. In 2017, collected data of Japan nationwide, multicenter, retrospective study on HDR monotherapy was published by Yoshioka et al. From 1995 through 2013, 524 patients, including 14% low-risk, 40% intermediate-risk, and 47% high-risk patients, were treated with HDR brachytherapy as monotherapy at 5 institutions in Japan. Patients >85% were treated with 7 to 9 fraction regimens. Respective 34%/58%/91% of low/intermediate/high-risk patients received ADT also. Median follow-up was 5.9 years. The 5-year biochemical control rates were 95%/94%/89% for low/intermediate/high-risk patients (Figure).

fractions of 9.5 Gy. Second, they used 2 implants, separated by 2 weeks, each with 2 fractions of 9.5 Gy. Finally, they adopted 3 implants, separated by 3 weeks, each with a single fraction of 11.5 Gy. Although their cohort included 25% of intermediate- and 20% of high-risk patients, they reported as high as 94% biochemical control rate at 5 years for the entire cohort. Strouthos et al. recently updated the results for the 3-fraction-in-3- implant cohort with 450 patients, showing a 5-year biochemical control rate of 95% with a prolonged median follow-up of 4.7 years, with late Grade 3 GU toxicity as 0.8% without any late Grade 3 GI toxicity. Similarly, Kukiełka et al. in Poland used 3 separate implants with single fraction per implant, but with 15 Gy each, and 45 Gy in total. Hoskin et al. in the UK started HDR monotherapy with 4-fraction regimen giving 34 or 36 Gy in total. Soon they changed their regimen into 31.5 Gy in 3 fractions, and then into 26 Gy in 2 fractions. Finally, they are investigating a single-fraction regimen. Their indication for HDR monotherapy was almost restricted only to intermediate- or high-risk patients, which is a similar concept to that of Yoshioka et al. in Japan, and also is characterized by a high rate of ADT use. Martinez and Krauss et al. compared 3 regimens, including the aforementioned 38 Gy in 4 fractions, 24 Gy in 2 fractions, and 27 Gy in 2 fractions. They found the acute and late toxicity profiles associated with these 3 HDR monotherapy schedules were similar and were well tolerated. Combined with the fact that the clinical outcomes were similar, they concluded that all 3 regimens may be acceptable options for the management of low- to intermediate-risk prostate cancer. SP-0350 HDR brachytherapy in one fraction vs LDR brachytherapy in the treatment of localized prostate cancer. Early results. P. Agoston 1 , T. Major 1 , K. Jorgo 1 , G. Fröhlich 1 , L. Gesztesi 1 , G. Stelczer 1 , C. Polgár 1 1 National Institute of Oncology, Centre of Radiotherapy, Budapest, Hungary Abstract text Aim: We conducted a prospective, randomized clinical trial to compare the toxicity and clinical outcome of a single fraction high dose rate (HDR) monotherapy and low dose rate (LDR) seed brachytherapy (BT) in early, organ confined prostate cancer. We report our early results of the first 100 patients recruited in the study. Study was registered at the national ethical committee with reference number 056501/2013/OTIG and on the clinicaltrials.gov with reference number NCT02258087. Patients and methods: Between January 2015 and June 2017, 100 patients (mean age: 65 years; range: 50-75 years) were randomized to receive either 145 Gy I-125 LDR BT (n=50) or a single fraction of Ir-192 HDR (n=50) BT. In the HDR-BT arm 48 patients were treated with 19 Gy and the last two patients with 21 Gy. Before randomization patients were stratified according to their risk group. Forty-four low risk (LR: PSA≤10, T1-2a, Gleason score≤6) and 56 selected intermediate risk (IR: PSA>10-15ng/ml or T2b-c, or Gleason score 3+4) patients were treated. The mean iPSA was 8.6ng/ml (range:0.5-15 ng/ml). The target volume in LR was the prostate, in IR the prostate with a 3mm margin. Dosimetric parameters for both modality were defined and registered (V100, V150, V200, DHI, COIN for the target, D r 2cm 3 for the rectum, Du10%, Du30% for the urethra). Prior to BT 58% of the patients received neoadjuvant endocrine treatment, which was stopped at the time of brachytherapy. Physical status, toxicity, international prostate symptom score (IPSS), PSA value were checked at 3 and 6 months after BT, than in every 6 months to 3 years and yearly thereafter. Acute side effect was registered within the first three months after BT, and late effects thereafter. Acute and late toxicity were

Late Grade 3 GU and GI toxicity rates were 1% and 0.2% at 5 years. Compared to American series, one distinct characteristic of Japanese series is that Japanese indication for HDR monotherapy included high-risk patients, and subsequently the use of ADT was more frequent than in the American series as will be described in the next section. 6- to 4-fraction HDR monotherapy: Demanes et al. at California Endocuriethérapy Cancer Center (CET) in the USA, started HDR monotherapy in 1996 with 42 to 43.5 Gy in 6 fractions, including 2 implants with 3 fractions each. With a median follow-up period of 6.5 years, they reported long-term results for 448 patients including 288 low-risk and 160 intermediate-risk patients. The actuarial 6- and 10-year PSA progression -free survival rate was 99% and 98%. Late Grade 3 to 4 GU toxicity rate was 5%, with GI 0%. Martinez et al. at William Beaumont Hospital (WBH) in the USA, launched HDR monotherapy with 38 Gy in 4 fractions in 1999. This 4-fraction regimen, which can be accomplished within 2 days, was introduced into Europe, at least into Germany and Switzerland. In general, American researchers seem to indicate HDR monotherapy for low- and favorable intermediate-risk patients, by contrast with Japanese or European researchers. 3- or 2-fraction HDR monotherapy: Three-fraction HDR monotherapy has been reported in early period from 3 countries including Australia, UK and Germany. Barkati et al. in Australia conducted a dose escalation study using 3 fractions of 10 Gy, 10.5 Gy, 11 Gy and 11.5 Gy. They successfully reached to the highest dose level, showing acceptable acute and late toxicities. Zamboglou et al. published the largest series of HDR monotherapy with >700 patients from a single institution in Germany. The transition of dose fractionations used by them looks interesting; first, they treated with 1 implant in 4