Evaluation of Treatment Response in Solid Tumors Using Recist 1.1 Criteria: A Radiological Study

Background: Radiological assessment plays a crucial role in monitoring treatment response in patients with solid tumors. The Response Evaluation Criteria in Solid Tumors (RECIST) version 1.1 provides a standardized framework for evaluating therapeutic outcomes and guiding clinical decision-making in oncology practice. Objectives: To evaluate treatment response in patients with solid tumors using RECIST 1.1 criteria and to assess the association between treatment response and selected clinicopathological characteristics. Methods: This retrospective observational study was conducted at Al-Thaqalayn Oncology Hospital, Basra, Iraq, from January 2025 to April 2026. A total of 150 patients with histologically confirmed solid tumors who underwent baseline and follow-up radiological examinations were included. Treatment response was assessed using RECIST 1.1 criteria and categorized as complete response (CR), partial response (PR), stable disease (SD), or progressive disease (PD). Demographic, clinical, and radiological data were collected and analyzed using SPSS version 31. A P value of less than 0.05 was considered statistically significant. Results: The mean age of the patients was 54.3 ± 12.8 years, and females constituted 58.0% of the study population. Breast cancer was the most common malignancy (28.0%), followed by colorectal cancer (18.7%) and lung cancer (16.0%). Metastatic disease was present in 58.0% of patients. According to RECIST 1.1 criteria, partial response was observed in 36.0% of patients, stable disease in 32.0%, progressive disease in 24.0%, and complete response in 8.0%. The objective response rate was 44.0%, while the disease control rate reached 76.0%. Treatment response was significantly associated with metastatic status (P value <0.001), primary tumor type (P value = 0.018), and patient age (P value = 0.028). Conclusions: RECIST 1.1 is an effective and standardized tool for radiological assessment of treatment response in patients with solid tumors. Most patients achieved disease control following treatment, and treatment response was significantly influenced by metastatic status, tumor type, and age. Radiological follow-up remains essential for evaluating therapeutic efficacy and supporting evidence-based oncology care.