Toxicity profile of polyradiomodification therapy used in the combination treatment for rectal cancer

Objective: to analyze the spectrum of toxic reactions associated with various polyradiomodification regimens used in the combination therapy for rectal cancer.

Materials and methods. We have conducted a retrospective analysis of the data from a prospectively collected database. We included patients with stages сT2–3N0M0 and сT2–3N1–2M0 resectable rectal cancer. Polyradiomodification regimens included a course of radiotherapy (5 × 5 Gy) with the following radiomodifiers: rectal administration of a biopolymer composition containing metronidazole (MZ)  at a dose of 10 g/m² (twice), intracavitary local microwave hyperthermia (three times on days 3–5) and oral capecitabine (Cap).

Results. The study included 241 participants. Toxic reactions were observed in less than 33.2 % of patients receiving polyradiomodification as a part of combination therapy. The most common adverse events were gastrointestinal toxicity and neurotoxicity, diagnosed in 28.6 % and 17.4 % of cases respectively. The frequency of toxic reactions was significantly higher in patients receiving Cap14 + MZ regimen than in those receiving Cap5 + MZ regimen (p = 0.0038). However, the inclusion of microwave hyperthermia in both Cap5 and Cap14 therapeutic regimens had no impact on the frequency of toxic reactions (44.2 and 31.5 % respectively, p = 0.146). The proportion of patients with grade III gastrointestinal toxicity did not significantly vary across the groups (p = 0.16).

Conclusion. The course of polyradiomodification included into the combination therapy for rectal cancer has an acceptable toxicity profile and can be used to improve long-term outcomes of combination treatment for rectal cancer.