ESTRO 2022 - Abstract Book

S1159

Abstract book

ESTRO 2022

Materials and Methods The study group consists of 23 patients with locally recurrent prostate cancer after prostatectomy and salvage (20; 87%) or adjuvant (3; 13%) radiotherapy, treated with salvage SBRT between 2014 and 2020, at a mean age of 69 years (51-80). The mean pre-SBRT PSA level was 4.62 ng/ml (0.008-39 ng/ml), 14 patients (61%) had ISUP Grade Group (GG) of ≤ 3, and 9 patients (39%) had GG ≥ 4. The average time between salvage/adjuvant RT and local recurrence was 5 years. The recurrence was retrovesical in 12 (52%), periurethral in 9 (39%), and both regions were involved in two (9%) patients. In 14 patients (61%) local recurrence was the only site of failure, whereas in 9 patients (39%) it was accompanied by oligometastatic regional (8; 35%) or distant lesions (1; 4%), which were also treated with SBRT. All patients were treated with focal SBRT to the local failure with dose per fraction ranging from 5 Gy to 12 Gy and the total dose ranging from 24 Gy to 36.25 Gy. The most common (12; 52%) SBRT schedule was 33.75- 36.25 Gy in 5 fractions. 11 patients (48%) were treated with CyberKnife, and 12 (52%) with linear accelerator. Fifteen patients (65%) continued or were given ADT together with SBRT. The treatment outcome was evaluated for biochemical response (BR) defined as the decrease of PSA below the pre-SBRT level, biochemical control (BC) defined as PSA value below 0.2 ng/ml, and overall survival (OS). All that end-points were calculated with an actuarial method. The chance of biochemical control was also assessed in relation to selected clinical factors. Results Median follow-up was 28 months. One- and 2-years OS were 95% and 85%, 1- and 2-years BR were 84% and 66%, and 1- and 2-year BC were 50% and 50%, respectively. The biochemical recurrence was observed in 50% and 75% of patients with GG of ≤ 3 and ≥ 4, respectively. Patients who experienced biochemical recurrence after SBRT had a mean pre-SBRT PSA value of 6.9 ng/ml as compared to 2.34 ng/ml in those with BC. The time between primary RT and local failure was 59 and 69 months, respectively. Despite numerical differences between some comparisons, none of the analyzed factors were statistically significant. Conclusion SBRT for locally recurrent prostate cancer after prostatectomy and radiotherapy may lead to the biochemical response in a majority of patients. However, the durable biochemical control is somewhat limited. Proper selection of patients can be of pivotal importance. Purpose or Objective Definitive or adjuvant/salvage pelvic RT can be used in treatment of prostate cancer.Hematotoxicity can be seen in patients who underwent pelvic RT since approximately %50-55 of bone marrow activity takes place in pelvic bone.In this study,we aimed to investigate the relationship between all pelvic bone dose parameters and subacute/chronic hematotoxicity in patients with prostate cancer who underwent pelvic RT Materials and Methods 74 patients treated with adjuvant/salvage or definitive pelvic RT between 2012-2020 were retrospectively evaluated.All pelvic bone was later contoured in with the upper border:L5 vertebra and crista iliaca;the lower border at levels of the inferior pubic ramus and femoral neck.The differential DVH parameters of this pelvic bone V3,V5,V10,V20,V30,V40,V50 and mean doses were subsequently calculated.WBC,hemoglobin(Hb),lymphocyte,neutrophil and PLT values were measured from hemogram parameters of the patients before treatment,6-12 months(subacute) and 12-18 months(chronic) after treatment.Hematotoxicity assessment was performed according to the Common Terminology Criteria for Adverse Events v5.0. If there was a grade 2 or higher toxicity in any of the whole blood parameters,it was accepted as hematotoxicity(HT2+) and relationship between late hematotoxicity and doses of pelvic bone was evaluated.Chi-square and Fisher's exact tests were used for analysis for categorical variables among independent groups Results vPSA levels were median 11.93(4-375)ng/dl; the median dose of RT to the prostate or tumor bed was 74(64-78)Gy,and the median dose of pelvic lymphatics alone was 46(44-54,4) Gy.IMRT and VMAT technique was used in 57 and 16 patients, respectively.The subacute blood results of 71 patients and chronic blood results 63 patients were obtained.A significant time-dependent decrease in values of WBC,Hb,PLT,lymphocytes,neutrophils were observed(p<0.001).As a result in comparison of these 5 individual parameters,the values of subacute and chronic period differed statistically significantly compared to the values before RT,while there was no difference between the values of subacute and chronic periods.HT2+ was observed in 29 patients and in 15 patients during subacute and chronic period,respectively.The median values for V3- V5-V10-V20-V30-V40-V50 of the pelvic bone were %97-%92-%86-%74-%58-%40-%17,respectively and the mean dose of pelvic bone was 33.4 Gy.When the relationship of all pelvic bone dose parameters was examined,no statistically significance was found between subacute or late HT2+ or any subgroup with toxicity.Variables such as type of treatment (postoperative vs definitive),age( ≤ 65vs>65),pelvic dose( ≤ 46vs>46),hormone therapy usage( ≤ 12 vs >12 months),RT technique(VMAT vs IMRT) were also associated with subacute/chronic hematotoxicity Conclusion A low decrease in blood values can be observed in prostate cancer patients undergoing pelvic RT in subacute or late period.In our study,no significant relationship was shown between pelvic bone doses and hematotoxicity PO-1366 The relationship between pelvic bone dose and hematotoxicity in prostate cancer patients I.A. kilinc 1 1 ankara university, The Department of Radiation Oncology, Ankara, Turkey