Advancing Radiotherapy Precision for Cervical Cancer: Reducing Setup Errors and Optimizing PTV Margins

Background & Objective: Radiotherapy plays a key role in cancer treatment, particularly in the treatment of pelvic cancers like cervical cancer, by delivering targeted radiation to the tumor. The present study was conducted with aim to highlight the significance of addressing setup errors in cervical cancer radiotherapy through the optimization of treatment margins, ultimately aiming to improve both treatment accuracy and patient outcomes.Materials & Methods: This retrospective study was conducted on 20 cervical cancer patients treated between January and September 2024, using knee and foot fixed supports for immobilization. Treatment setups were verified with electronic portal imaging and delivered via an Elekta linear accelerator. Displacement analysis assessed setup errors using bony landmarks, and safety margins were calculated based on ICRU-62 guidelines and Stroom’s and Van Herk’s formulas.Results: The findings revealed systematic errors of up to 0.22 cm and random errors of 0.74 cm (X-axis), 0.2 cm and 0.08 cm (Y-axis), and 0.18 cm and 0.08 cm (Z-axis). The calculated CTV-PTV margins were 0.61 cm, 0.57 cm, and 0.51 cm along the X, Y, and Z axes (Van Herk’s formula), 0.5 cm, 0.46 cm, and 0.42 cm (Stroom’s formula), and 0.23 cm, 0.22 cm, and 0.2 cm (ICRU-62 guidelines). Based on these findings, a 6 mm safety margin is recommended as optimal.Conclusion: This study demonstrates that image-guided verification using electronic portal imaging improves accuracy, reduces setup errors, and supports the implementation of a 6 mm safety margin in pelvic radiotherapy, enhancing both treatment precision and patient quality of life.