The importance of maintenance chemotherapy in the first and second lines of treatment of metastatic colorectal cancer.

Abstract

e15583 Background: The first and second lines of CT is decisive in the treatment of colorectal cancer. Choosing the right one allows you to increase PFS and improve long-term results. Surgical treatment and maintenance chemotherapy (MT) increase PFS and OS, as they can be prescribed at any stage of treatment. Methods: The analysis included 192 patients diagnosed with metastatic colorectal cancer (mCRC) who received treatment between 2014 and 2019. The average age of the patients was 62 years. At the beginning of treatment, the overall condition of all patients was ECOG1. Primary mCRC had 129 (67%) patients. In 63 (33%) patients, locally advanced disease was first diagnosed, which were included in the study after progression. PFS and OS for all patients were calculated from the start of the 1st line. Localization of the primary tumor in 42 (22%) patients was on the right side of the colon and on the left side in 149 (78%) and 1 patient did not show primary tumor. Among the patients with primary metastatic disease, 100 (52%) had isolated metastases, while the remaining 92 (48%) had 2 or more localizations. Different types of surgical treatment of metastases in the liver occurred in 41 (21%) patients. 119 patients never received MT (with any number of lines) and made a comparison group(A). 73 patients received MT in at least one of the CT lines (B). 12 patients received MT in the 1st and 2nd CT (C). These groups were homogeneous in terms of gender, age, ECOG, accessibility of surgical treatment of distant metastasis, mutational status of the tumor, and accessibility of biotherapy. Evaluation of the effect was performed using RECIST criteria, at intervals of 3 months or the appearance of clinical symptoms of progression. The treatment was carried out before the progression. At the time of analysis, 94 patients are alive and continue to receive treatment. Results: We compared in all three groups: In group A: OS - 12.9 months, PFS 1-line CT - 9.5 months, PFS 2-line CT - 4.5 months In group B: OS - 27.6 months, PFS 1-line CT - 13.6 months, PFS 2-line CT - 9.1 months In group C: OS - 38.3 months, PFS 1-line CT - 14.2 months, PFS 2-line CT - 9.1 months. “Five-year” survival (In those patients who were observed from the start of the study for all 5 years) in group A was 5,8 %, in group B 15 %, and in group C 16 %. Conclusions: Increase of PFS and OS in patients who received MT at least at one of the stages of treatment, and continues to increase in patients receiving MT in the first two lines CT. Thus, MT is a necessary component of the treatment of mCRC.