Modulated Electro-Hyperthermia in Combination With Multimodal Therapy for Locally Advanced Rectal Cancer

The goal of this clinical trial is to investigate if the addition of modulated electro-hyperthermia (mEHT) improves tumor down-staging and pathological response in adult patients (20 years and above) with locally advanced rectal adenocarcinoma (cT3N0M0 with high risk of recurrence, cT3N1-2M0, or cT4N0-2M0). The main questions it aims to answer are: * Does the addition of mEHT to the Total Neoadjuvant Therapy (TNT) regimen significantly increase the rate of tumor down-staging (ypT and ypN) compared to TNT alone? * Does the combination therapy improve the pathological complete response (pCR) rate and long-term outcomes (such as disease-free survival) compared to standard TNT? Researchers will compare participants randomized to receive Total Neoadjuvant Therapy (TNT) plus mEHT using the Oncotherm EHY-2030 device to participants receiving TNT alone to see if the adjunctive mEHT therapy enhances tumor regression and improves patient prognosis. Participants will be randomized (1:1) into one of the two groups and will undergo the following regimen: * Receive standard TNT, which includes 5-6 weeks of chemoradiotherapy (CRT) followed by 4-6 months of neoadjuvant chemotherapy. * Patients in the experimental group will receive mEHT twice a week during the CRT period.