2061 - Effect of Combined Deep Hyperthermia Therapy on Radiation Proctitis in Patients with Rectal Cancer Receiving Neoadjuvant Chemoradiotherapy: A Single-Center Case-Control Study

Purpose/Objective(s): To investigate the effect of combined deep hyperthermia therapy (dH) on radiation proctitis in patients with rectal cancer receive neoadjuvant chemoradiotherapy(nCRT).

Materials/Methods: This single-center randomized controlled study enrolled patients with locally advanced rectal cancer from January 31,2023 to January 31,2024. Patients were randomized 1:1 to receive neoadjuvant chemoradiotherapy(nCRT) or nCRT combined deep hyperthermia therapy(dH). The nCRT consisted of intensity-modulated conformal radiotherapy (IMRT) at a dose of 45–50.4 Gy in 25–28 fractions, 1.5–2.0 Gy per fraction, combined with concurrent chemotherapy of capecitabine at 825 mg/m2 twice daily. Patients in nCRT+dH group received additional deep hyperthermia on the 1st, 6th, 11th, 16th, and 21st days of radiotherapy, for a total of 5 sessions.Radical resection of rectal cancer was performed 8–12 weeks after completion of nCRT. The primary endpoints were:To compare the incidence of grade 2–3 acute radiation proctitis (ARP) during radiotherapy between the two groups.To compare the incidence of radiation enteritis in postoperative tissue specimens between the two groups.A statistically significant difference between groups was defined as the primary comparison of interest.

Results: All patients completed treatment with excellent compliance.A total of 32 patients were enrolled (nCRT+dH group vs. nCRT group).The median age ( 61 vs. 62 ), KPS=80 (93.8% vs. 87.5%) .During the first 8 weeks of treatment, the incidence of grade 2–3 acute radiation proctitis (ARP) was significantly higher in the nCRT+dH group than in the nCRT group (100% vs. 68.75%, P = 0.043).There was no significant difference between the two groups in the proportion of patients with histopathological evidence of proctitis (including acute and chronic changes) after surgery nCRT+dH vs nCRT (31.25% vs. 37.5%, P = 0.734).Notably, the median time to the occurrence of grade 2–3 ARP was significantly shorter in the nCRT+dH group (1.3 weeks vs. 2.1 weeks, P = 0.008).In the nCRT+dH group, 3 patients discontinued radiotherapy due to severe acute radiation proctitis.

Conclusion: In neoadjuvant concurrent chemoradiotherapy for rectal cancer, the addition of deep hyperthermia was associated with an increased incidence and significantly earlier onset of acute radiation proctitis. These toxicities may potentially result in premature interruption of radiotherapy, which could compromise treatment efficacy. Nevertheless, the incidence of acute and chronic radiation proctitis in surgical specimens was not elevated following the acute phase.According to the results of this study, combined deep hyperthermia with neoadjuvant chemoradiotherapy is not currently advocated in patients with rectal cancer. Further long-term follow-up of the enrolled patients is warranted to evaluate its impact on overall local control rates.