EFFICIENCY OF POSITRON EMISSION TOMOGRAPHY IN PREDICTION OF RESPONSE AFTER CHEMORADIOTHERAPY FOR RECTAL CANCER

Kaganov Oleg I., Frolov Sergey A., Blinov Nikita V., Okulevich Nikita B.

Personification of approaches to the treatment of patients with rectal cancer requires precise staging and identification of unfavorable prognosis factors. The choice of the most effective treatment protocol directly depends on the response of the tumor to chemoradiotherapy. The purpose of this study is to evaluate the ability of ¹⁸F-fluorodeoxyglucose positron emission tomography combined with computed tomography to predict tumor response to neoadjuvant treatment. Materials and methods. The study included 32 patients diagnosed with locally advanced rectal cancer. All patients were planned to undergo combined treatment: neoadjuvant chemoradiation therapy, as well as surgical intervention, total mesorectumectomy after 10-12 weeks. Patients underwent ¹⁸F-fluorodeoxyglucose positron emission tomography combined with computed tomography at the stage of staging, as well as 8 weeks after completion of chemoradiotherapy. Decrease of standardized uptake values before and after therapy was assessed. The correlation of the obtained data with the degree of tumor response to chemoradiation according to the Mandard scale was studied. Results. Patients with a good response to neoadjuvant treatment – 6 patients (Grade 1-2 on the Mandard scale); patients with a poor response– 25 patients (Grade 3-4 on the Mandard scale). It was shown that before and after neoadjuvant treatment, the mean standardized uptake values was 15.2 and 5.2, respectively (p<0.001). It was demonstrated that a reduction in standardized uptake values after chemoradiotherapy by more than 72% could help identify patients who are more likely to respond to treatment with a sensitivity of 80,2%, specificity of 78.4%, and accuracy of 77%. Thus, ¹⁸F-fluorodeoxyglucose positron emission tomography can be used by oncoboard to assess the effect of neoadjuvant treatment when making strategic decisions for patients with rectal cancer.

Keywords:rectal cancer, ¹⁸F-fluorodeoxyglucose positron emission tomography, complete response, chemoradiotherapy