Which of the following indicates a significant increase in the risk of errors in radiotherapy?

The absence of a Quality Assurance (QA) program is critical in ensuring patient safety and treatment accuracy in radiotherapy. A QA program is designed to systematically monitor and evaluate the various processes involved in radiation delivery, including equipment performance, treatment planning, and patient verification. When a QA program is absent, there is no structured framework to identify and rectify potential errors prior to treatment. This can lead to significant risks, including incorrect doses being delivered, misalignment in treatment setups, and overall compromised patient safety. This lack of oversight can cause variability and increase the chance of mistakes in the administration of therapy, making it a significant factor in error risk.

In contrast, high accuracy in output, reduced patient throughput, and consistency in treatment plans are factors that typically contribute to lower error rates. High accuracy implies reliable machine performance and dose delivery, reduced patient throughput can allow for more careful treatment planning and execution, and consistency in treatment plans indicates that processes are standardized and well-monitored. Thus, the absence of a QA program stands out as a critical condition that heightens the likelihood of errors in treatment delivery.