Failure mode and effect analysis (FMEA) is a common management tool for analysing the causes and consequences of possible failures in different cancer treatments, goods, processes, systems, and services. As a result of individual differences in reason and cognition as well as the impact of social ties, the experts involved in an FMEA with many participants may have conflicting effects on the decision-making process. Incomplete weights of risk variables are also essential for reflecting the uncertainty with which experts see a situation. As a result, a consensus-based FMEA approach is proposed to investigate stereotactic body radiation therapy (SBRT) for lung cancer. First, we identified the failure modes of SBRT of lung cancer and then analysed their effect on the treatment process. Generally, the choice of lung cancer treatment is usually made by oncology experts, who select the most suitable option for the patient. However, the oncology expert’s bounded personality and rationality characteristics can influence the patient’s treatment choice. Moreover, the American Cancer Society states that the patient’s treatment choice may vary depending on the oncology expert. Therefore, we propose a group decision-making model (GDM) for FMEA of lung cancer treatment in a linguistic Z numbers environment to enhance the survival rate of lung cancer patients.