ESTRO 2023 - Abstract Book

S1249

Digital Posters

ESTRO 2023

treatment-related. To optimise future MRgRT regimes and supportive care, toxicity monitoring of weekly ePROs ensures timely detection of changes in patient-perceived AEs.

PO-1537 What factors may influence late urinary toxicities after radiation therapy of prostate cancers?

N. Fourati 1 , M. Frikha 1 , S. Zouari 1 , F. Dhouib 1 , W. Siala 1 , L. Farhat 1 , W. Mnejja 1 , J. Daoud 1

1 Habib Bourguiba Hospital Faculty of Medicine University of Sfax, Radiotherapy Department, Sfax, Tunisia

Purpose or Objective The purpose of the study was to evaluate the predictive factors of late urinary toxicities in patients treated with radiotherapy for prostate cancer at our department. Materials and Methods Between November 2011 and January 2019, 181 patients were treated, in our department, for prostate cancer by definitive radiotherapy without or with hormonotherapy. A total of 178 patients (98.3%) were included in this retrospective study. All patients were treated according to conformal technique with intensity modulation (IMRT) for 142 patients (78.5%) and without (RT3D) for 39 patients (21.5%). Acute and late urinary toxicities were reviewed and graded according to the RTOG scale. Clinical factors which could influence the occurrence of late toxicities were collected. From the dose volume histograms (HDV), the volume of the bladder wall, the percentage of the volume which receives 70Gy (V70Gy), 60Gy (V60), the median dose D50%, the maximum dose (Dmax), the mean dose (Dmoy) and minimum dose (Dmin) of bladder wall were also collected. Results The median bladder wall volume was 89 cm ³ [32.6-295.8]. The respective median of V70Gy and V60Gy were 21.2% [0-84.4] and 32.4% [0.4-100]. The dose constraint V70 < 25% was respected in 125 patients (69.8%) and V60 < 50% in 167 patients (93.3%). During RT 164 patients (92.1%) developed urinary toxicities which was RTOG grade ≥ 2 in 46 patients (25.8%). Aggravation of the initial symptomatology was noted for 112 patients (62.9%) and 66 patients (37.1%) had stability of their initial symptomatology. Late urinary toxicities data were available for 177 patients (97.8%) which were grade ≥ 2 for 15 patients (8.5%). Ten patients (5.7%) had a deterioration of their symptomatology compared to the end of radiotherapy course. An improvement was noted in 108 patients (61%). In univariate analysis, age, acute urinary toxicities ≥ G2, and the presence of urinary symptoms before the start of RT were predictive factors of late urinary toxicities. No urinary late toxicities Urinary late toxicities p Age (years) (Mean±SD) 68±7.5 71.3±6.2 0.002

RT3D IMRT

25.2% 74.8% 72.8% 27.2% 58.4% 14.6%

17.6% 82.4% 70.3% 29.7% 81.1% 18.9% 64.9% 35.1% 35.1% 64.9% 94±31

0.22

No lymph node irradation Lymphnode irradiation

0.71

No smokin Smoking

0.44

No acute urinary toxicities ≥ G2 Acute urinary toxicities ≥ G2 No urinary symptoms before RT Urinary symptoms before RT

83% 17%

0.006

66.3% 33.7%

<0.001

0.16 0.64 0.33 0.16 0.18

Bladder wall (BW) volume (cc) (Mean±SD) 102±43.7

V70 BW (%) (Mean±SD) V60BW (%) (Mean±SD) D50 BW (Gy) (Mean±SD) Dmoy BW (Gy) (Mean±SD)

19.8±8.7 33.7±15.6 39.8±16.2 43.7±11.4

20.4±11

31.5±13.5 36.3±16.6 41.4±11.5

Conclusion The results of our study suggest that late urinary toxicities are more related to clinical factors (age, importance of initial symptomatology, and occurrence of acute toxicity > G2) than to dosimetric ones (volume of the bladder wall and doses received at its level). This underlines the importance of paying particular attention to these parameters, especially since dose constraints are generally respected with IMRT.

PO-1538 Urinary and bowel dysfunction after hypofractionated 20x3 vs 7x6.1 Gy for localized prostate cancer

K. de Vries 1 , L. Incrocci 1 , F. Sinzabakira 1 , E. Berenschot 1 , M. Christianen 1 , M. Franckena 1 , F. Froklage 1 , W. Heemsbergen 1

1 Erasmus MC Cancer Institute, Radiotherapy, Rotterdam, The Netherlands