ESTRO 2022 - Abstract Book

S351

Abstract book

ESTRO 2022

Conclusion In our patient group, most propagated contours were able to produce a plan close to the gold standard. Contour correction would be recommended in high dose and high dose gradient organs. The replans calculated in this study have an increased complexity, so deliverability should be further assessed. Further work on patients with large changes is required to evaluate the generalisability of our conclusions. ¹ Marchant, T.E. et al., Phys Med Biol, 2008, ² McGarry, C.K. et al, Br J Radiol, 2015.

Poster Discussion: 10: Urology 1

PD-0407 A new approach to imaging and rapid microbiome identification in prostate cancer patients

D. Gabrys 1 , E. Ma ś lak 2 , M. Z ł och 3 , P. Pomastowski 3 , F. Monedeiro 3 , B. Buszewski 2 , J. Mrochem-Kwarciak 4 , K. Bojarska 4 , W. Mi ś ta 1 1 Maria Sklodowska-Curie National Research Institute of Oncology, Radiotherapy Department, Gliwice, Poland; 2 Nicolaus Copernicus University, Centre for Modern Interdisciplinary Technologies and Department of Environmental Chemistry and Bioanalytics, Faculty of Chemistry, Toru ń , Poland; 3 Nicolaus Copernicus University, Centre for Modern Interdisciplinary Technologies, Toru ń , Poland; 4 Maria Sklodowska-Curie National Research Institute of Oncology, Analaytical and Clinical Biochemistry Department, Gliwice, Poland Purpose or Objective Little is known about the impact of urinary microflora and its effects on side effect after radiotherapy (RT). Until recently, any growth of bacteria grown from urine was considered invasive. A new look at the issue of the composition and significance of the urinary microbiome may bring the use of the mass spectrometry identification method MALDI. This study aims to use the MALDI technique to identify the microbiome of urine samples collected from pts treated with radiotherapy for prostate cancer. Materials and Methods We included 52 pts treated for prostate cancer irradiated with radical intent. Blood and urine samples were collected before the gold marker implantation, on the day of beginning RT, last day of RT, 1 month after RT. It is recommended to collect urine from the midstream, but not always pts do it correctly despite being instructed. Therefore, we decided to collect samples from first-void and midstream in 12 pts for MALDI, from remaining pts we collect two samples from midstream-void for MALDI and biochemical analysis. Results Microorganisms were present in 145/186 urine samples. Using three different culture media the best microbial growth was observed on TSA (universal medium) and CLED (differential medium for urine specimens) – the largest number of isolates was obtained. We found 33 different species – 3 G(-) and 30 G(+). The most frequently isolated strains were: Staphylococcus haemolyticus (19%), Staphylococcus epidermidis (18%), Staphylococcus hominis (16%), Enterococcus faecalis (13%), and Micrococcus luteus (10%). When comparing the type of urine samples, bacteria were more common in the samples from the first-void urine than from the midstream one. The absence of bacteria was found in 12.2% of samples from the first-void urine and 24.7% from the midstream. Overall, the ratio of the number of detected species per number of samples corresponding to the first and middle stream were 1.80 and 1.71%, respectively. The differences in the total incidence of species between streams did not present to be significant (p=0.85), but the number of bacterial species in the initial stream was generally greater. The amount of bacterial species found in urine depended on the treatment. Before gold fiducial implantation the total number of detected bacterial species was significantly higher in comparison to the end of radiotherapy (p=0.038) indicating that the administered therapy results in depleting the local microbiome (Fig. 1). One month after radiotherapy an increase in the number of isolated bacteria was observed. The number of bacterial species in urine did not correlate with the blood parameters. The presence of leukocytes (p=0.013) and proteins (p=0.004) in urine were related to a greater variety of bacteria found in urine specimens.