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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

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

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

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