S194
Clinical - Biomarkers of clinical response
ESTRO 2026
Stockholm, Sweden. 4 Department of Nuclear Medicine and Medical Physics, Karolinska University Hospital, Stockholm, Sweden
collected after a median of 87 days (range:62–117). However, PCA3 mRNA over-expression demonstrated to be suppressed in the follow-up urine samples.
Purpose/Objective: One third of patients receiving postoperative
radiotherapy for breast cancer develop grade 2 or greater radiation dermatitis, with incidence varying by fractionation schedule (1). The single nucleotide polymorphism rs1801516 in the DNA repair gene ataxia telangiectasia mutated (ATM) was associated with high/intermediate/low risk (AA/AG/GG, respectively), while elevated levels of the inflammatory marker high - sensitivity C - reactive protein (hsCRP) (3) were associated with severe acute skin reactions from radiotherapy. The objective was to determine whether acute radiation dermatitis in breast cancer patients can be predicted by analysing genetic variants and inflammatory biomarkers in peripheral blood. Material/Methods: This prospective, non-randomized clinical cohort study included 200 patients. A targeted blood sample analysis before radiotherapy was performed to analyse ATM SNP rs1801516 while hsCRP and the inflammatory cytokine interleukin - 6 (IL - 6) were measured from blood collected before start and after radiotherapy was completed. Acute skin reactions were assessed at baseline, after completion of radiotherapy and after one year by specially trained nurses using the Radiation Therapy Oncology Group (RTOG) acute radiation morbidity scoring criteria. Results: The median age was 63 years (range 40-87) and BMI 25.5 kg/m2 (range 17.8-43.7). 131 patients received 26 Gy in 5 fractions and 66 patients 40 Gy in 15 fractions (two patients with a boost to 48 Gy in 15 fractions). Acute radiation dermatitis after completion of radiotherapy was: RTOG grade 0 in 47 patients (24%), grade 1 in 128 patients (64%), and grade 2 in 16 patients (8%). The low prevalence of grade 2 toxicity was in line with a relatively unaltered inflammatory response, where median hsCRP concentration before treatment was 1.3 mg/L (range 0.2-126) and after treatment 1.2 mg/L (range 0.2-62), and similarly, IL-6 concentration was 2.9 ng/L (range 0.25-55) and 2.75 ng/L (range 1.20-61). Genotyping for rs1801516 yielded 3 AA homozygotes (1.5%), 51 AG heterozygotes (26%), and 145 GG homozygotes (73%). In a proportional-odds ordinal logistic regression of end- of-treatment RTOG toxicity (grades 0–2; n = 167), receiving 40 Gy (vs 26 Gy) was associated with higher odds of being in a higher toxicity grade (OR = 2.55 (CI:1.22-5.33), p = 0.013). IL-6, hsCRP, genotyping for rs1801516, and BMI were not statistically significant. Conclusion: We observed substantially less skin toxicity compared to previous reports, with only 8% of patients having a
Conclusion: This is the first study evaluating the PCA3-s change following SBRT and ADT. Our findings reveal that, patients with high-risk factors have lower than expected PCA3-s, suggesting the need for a new cut- off value for this group. ADT and SBRT appear to suppress PCA3 mRNA overexpression in entire cohort. Thus, detectable post-treatment PCA3 level might be a sign of treatment failure. Keywords: Prostate cancer, PCA3, SBRT Mini-Oral 3430 Prediction of individual normal tissue radiosensitivity during radiotherapy for breast cancer patients, the role of genetic and inflammatory markers. Mattias Hedman 1,2 , Prabodha Kumar Meher 3 , Filippo Schiavo 2,4 , Zuzana Kocibalova 3 , Eva Onjukka 2,4 , Lovisa Lundholm 3 1 Department of Radiotherapy, Karolinska University Hospital, Stockholm, Sweden. 2 Department of Oncology-Pathology, Karolinska Institutet, Stockholm, Sweden. 3 Department of Molecular Biosciences, The Wenner-Gren Institute, Stockholm University,
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