Aim. To investigate the relationship between blood plasma biochemical indicators in patients with solid tumors before a treatment and after the first course of chemotherapy with objective treatment response. Methods. Blood plasma samples taken from 14 patients with cancer relapse were studied before the treatment and after the first course of specific chemotherapy (carboplatin, methotrexate, vinblastine in patients with urine bladder cancer and irinotecan, leukovorin and fluorouracil in patients with colorectal cancer). The first group included patients with colorectal cancer relapse (males — 3, females — 4) aged 57-62 years. The second group included patients with urine bladder cancer relapse (males — 5, females — 2) aged 48-64 years. Free radical activity and protein oxidative modification, as well as endogenous intoxication and major mineral and trace elements levels were studied. Results. When achieving the objective chemotherapy effect in patients after the first treatment course, an increase of alpha-1 globulin and gamma globulin level, as well as an increase of phosphorus, zinc, lithium and iron blood plasma level was observed. In case of following disease progression, the opposite dynamics of above-mentioned indicators was revealed. In patients with good objective effect of polychemotherapy after the first treatment course, a significant increase of endogenous intoxication and blood plasma free radical activity decrease were observed. If the following tumor progression was observed, the tendency of blood plasma free radical activity increase, accompanied by the total protein oxidative modification activation, was revealed after the first treatment course. Conclusion. The increase of alpha-1 and gamma globulin levels, as well as an increase of phosphorus level in blood plasma after the first course of polychemotherapy can be used as prognostic factors of anticancer therapy efficiency. High level of endogenous intoxication as well as an increase of copper, iron, zinc and lithium blood plasma concentrations can be applied as the additional markers.