Quantitative indicators of TREC and KREC excision circles in malignancies: a prospective cohort study

Background. In oncology, of particular interest is the study of the T-cell receptor excision circles (TREC) and the κ-deletion B-cell receptor excision circles (KREC), which are extrachromosomal DNA structures. In many malignancies, the effectiveness of immune checkpoint inhibitors depends on the mutational load of the tumor, which correlates with the formation of specific antitumor immunity. Quantitative indicators of recombination excision circles reflect the occurrence of a different repertoire of T-cell receptors, an integral component in the formation of specific immunity. Understanding the change in quantitative values of TREC and KREC in cancer patients can improve the selection of patients for immunotherapy.

Aim. To determine quantitative indicators of TREC and KREC for immunological evaluation of patients with malignancies.

Materials and methods. The study included 55 healthy individuals and 180 patients with malignancies. Among healthy individuals, 49.1% (27/55) were males and 50.9% (28/55) females. Among patients with malignancies, 20.5% (37/180) were males and 79.5% (143/180) females. The median age in healthy individuals was 36 years [Q1–Q3: 26–58]. The median age in the group of patients with malignancies was 57 years [Q1–Q3: 47.5–67].

Results. In the general population of healthy individuals, the median TREC level was 60.1 [Q1-Q3: 31.3-188.9] and the median KREC level was 256 [Q1-Q3: 149.8-353]. In the general population of patients with malignancies, the median TREC rate was 4.6 [Q1-Q3: 0.9-17.3] and the median KREC was 111.9 [Q1-Q3: 29.3-339.28]. According to the results of the study, we noted statistically significant differences in TREC and KREC indices between all patients with malignancies and healthy individuals (p<0.001, p=0.001). Analysis of TREC and KREC indices in patients with malignancies of various localizations (breast cancer, ovarian cancer, lung cancer, colorectal cancer, skin melanoma, lymphomas) in comparison with healthy individuals statistically significant differences in TREC level were noted (p=0.001, p<0.001). When analyzing the KREC level in the studied groups, statistically significant differences in patients with ovarian malignancies (p<0.001), lymphoma (p<0.001), colorectal cancer (p=0.001) and melanoma (p=0.039) in comparison with healthy individuals were obtained. When comparing groups pairwise, it was found that TREC level in patients with malignancies in the age group of 25–44 years was significantly higher than in the age group of 45–60 years (p=0.03); TREC level in the age group of 25–44 years was significantly higher than in the age group of persons over 60 years (p<0.001); TREC level in the age group of 45–60 years was significantly higher than in the age group over 60 years (p<0.001). Statistically significant differences of KREC level in the studied patients with malignancies depending on the age group were not established (p=0.16), there were no age differences of groups by KREC level.

Conclusion. The results demonstrate a significant decrease in TREC and KREC levels in patients with malignancies compared to healthy individuals. The study of TREC and KREC excision circles in peripheral blood is one of the promising approaches for the immunological evaluation of cancer patients.