ESTRO 2025 - Abstract Book

S1221

Clinical – Lower GI

ESTRO 2025

Purpose/Objective: The association between the pretreatment inflammatory biomarkers and treatment response has been established in various cancers. The aim of our study is to investigate the correlation between treatment response and hematological inflammatory biomarkers and/or the lung immune prognostic index (LIPI) score in locally advanced rectal cancer (LARC) patients treated with total neoadjuvant therapy (TNT). Material/Methods: Sixty-two LARC patients treated with TNT were included. Male/female ratio was 36/22 , and median age was 60 (41 84) years. Clinical T stage was T2 in 7 patients, T3 in 53, and T4 in 2. Clinical N stage was N0 in 7 patients, N1 in 42, and N2 in 13. Thirty-eight patients had distal tumors, located within 5 cm from the anus. All patients received 50-56 Gy to the primary tumor and 45-50.4 Gy to the regional lymph nodes with concurrent capecitabine followed by 4-6 cycles of capecitabine ± oxaliplatin. Treatment response was evaluated with digital rectal examination, magnetic resonance imaging, and colonoscopy 6-8 weeks after completing TNT. Patients with no evidence of residual disease were determined as clinical complete responders and observed without surgery (n=25). Thirty-seven patients underwent surgery, seven of these patients achieved a pathological complete response (pCR). Patients with clinical complete response (cCR) or pCR were classified as complete responders (CR), and the other response groups as non-complete responders (nCR). Thirty-two patients had CR and 30 were non-complete responders. Pre-treatment absolute values of neutrophils (N), lymphocytes (L), monocytes (M), and platelets (P), plateletcrit (PCT), mean platelet volume (MPV), mean corpuscular volume (MCV), neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), and platelet-to-lymphocyte ratio (PLR) were assessed as hematological inflammatory biomarkers. LIPI score was calculated using absolute NLR and serum lactate dehydrogenase (LDH) levels. Independent t-test and chi square test were used to analyse the relationship between treatment response and hematological inflammatory biomarkers and/or LIPI score. Results: Pretreatment N (p<0.001), M (p=0.013), P (p=0.025), NLR (p<0.001), and PLR (p=0.001) were significantly lower, while LMR (p<0.001) was higher in CR group compared to nCR group. Pretreatment L (p=0.245), PCT (p=0.624), MCV (p=0.801), and MPV (p=0.821) did not have any significant effect on the treatment response. Additionally, patients with good LIPI score had higher CR rates compared to those with poor LIPI score (p= 0.014).

Conclusion: Inflammatory biomarkers offer a simple and cost-effective way to predict treatment response in patients with locally advanced rectal cancer undergoing total neoadjuvant therapy.