Effectivness of a shortened cycle of monoimmunotherapy in NSCLC.

e21179 Background: Monoimmunotherapy for NSCLC is performed in all patients with a high level of PD-L1 expression ( > 50%) or patients with severe comorbidity and contraindications to therapy with platinum drugs with intermediate level of PD-L1 expression (1-49%).Therapy is carried out up to 2 years, disease progression or intolerable toxicity. An important issue is determining the optimal duration of treatment in order to find a balance between effectiveness, toxicity, cost and burden on the healthcare system. To date, there are no prospective studies with sufficient power devoted to this issue. Methods: The analysis included patients with histologically verified inoperable NSCLC who received the first line of therapy in 2018-2020. 25/230 patients received monoimmunotherapy in the first line (16 men, 9 women; mean age 65.4 years; PD-L1 level > / = 50% - 18 patients (72%), 1-49% - 3/25 ( 12%), 0% - 1/25 (4%), not assessed - 3/25 (12%), adenocarcinoma - 13 (52%), squamous cell - 12 (48%); All patients received pembrolizumab therapy 200 mg 1 once every 21 days. Results: The mean follow-up time was 5.3 months (95% CI 3.4–7.2). The average number of immunotherapy injections (min-max) is 6.4 (1–28). The objective response rate (ORR) in 1 line was 16/23 (64%) (complete regression - 2 patients (8%), partial regression - 3 (12%), stabilization - 11 (44%), progression - 3 (12 %), not assessed - 6 (24%), 2 (8%) patients died after the 1st injection of immunotherapy. Before the progression of the disease or until the end of the planned duration, 16 (64%) of 25 patients interrupted therapy: (10/16 (62%) due to the tightening of the requirements of the epidemiological situation, 6/16 (38%) refused to visit medical institutions. Average follow-up after the end of treatment 7.0 (1.3 - 12.2) months (min-max). 11/16 (68%) are observed without progression 9.3 months (4.0 - 12.1) (min-max PD in 4/16 (25%) after a mean follow-up time of 4.4 months (2.9 - 7.9) (min-max), 1 (6%) patient was lost to follow-up. Conclusions: The obtained data indirectly indicate the absence of a tendency towards a decrease in mPFS and mOS in the group of NSCLC patients who received MIT in the first line of treatment, for whom treatment was discontinued unscheduled, and not continued until 2 years or until the progression of the tumor process was recorded.