Adaptive Target Volume and Dosimetry in Image-Guided Radiotherapy for Cervical Cancer.

Background: Cervical cancer treatment with advanced radiotherapy techniques benefits from image guidance, particularly when anatomical changes occur during therapy. This case emphasizes the need for adaptive radiotherapy when target volume shifts significantly. Methods: A 70-year-old woman with International Federation of Gynecology and Obstetrics (FIGO) IIIC2 9th edition cervical squamous cell carcinoma presented with a distended uterine cavity due to fluid accumulation. She underwent definitive chemoradiotherapy using Volumetric Modulated Arc Therapy (VMAT) and weekly cisplatin. Results: Daily Cone Beam Computed Tomography (CBCT) imaging revealed progressive uterine shrinkage as intrauterine fluid drained, significantly altering target volume and organ-at-risk (OAR) positioning. These changes necessitated two re-planning CT scans during external beam radiotherapy to maintain accurate dosing and avoid OAR toxicity. The patient completed treatment, including image-guided brachytherapy, without complications. Adaptive planning ensured adequate tumor coverage and minimized normal tissue exposure. Conclusions: This case highlights the critical role of daily CBCT in detecting anatomical changes during radiotherapy. Adaptive re-planning, though rarely required more than once, was essential here to preserve treatment accuracy. CBCT should be considered a standard verification tool in cervical cancer radiotherapy, particularly in cases involving intrauterine fluid.