Plan-of-the-Day Adaptive Radiotherapy in Cervical Cancer: A Dosimetry and Clinical Feasibility Study

Introduction: Cervical cancer is prone to potentially large and frequent inter-fractional anatomical variations due to bladder and rectal filling that can compromise target coverage and increase organ at risk dose (OAR). While internal target volume (ITV) methods account for this, they often increase bowel exposure. We evaluated a Plan-of-the-Day (PoD) adaptive radiotherapy approach using a plan library to optimize coverage while reducing OAR dose.

Methodology: Eleven patients with stage IB–IVA cervical cancer received neoadjuvant chemotherapy followed by concurrent chemoradiation (45 Gy/25 fractions with 55 Gy SIB to pelvic nodes), weekly cisplatin, and image-guided brachytherapy. CT simulations with empty- and full-bladder protocols generated corresponding PTVs (EB-PTV and FB-PTV) for the plan library. Daily CBCT guided Plan-of-the-Day selection based on anatomical variations. Primary endpoint was OAR dose reduction; secondary endpoints were acute GI and GU toxicity.

Results: A total of 11 patients (median age 60, median stage III) contributed 275 fractions. Daily plan selection proved feasible, with 93% of fractions treated using the full bladder plan and only 7% requiring the empty-bladder plan. FB planning demonstrated superior dosimetry, achieving a median PTV V95 of 99% compared with 93% for EB (p<0.05). It also improved OAR sparing, reducing bladder V40 from 57.4% to 48.7% (p<0.05) and lowering irradiated small bowel volume by a median of 114 cm³ (62% relative; p < 0.05). These findings affirm the dosimetric benefits of a full-bladder PoD adaptive approach. Acute grade >= 2 GU and GI toxicity reported in 18% and 20% respectively.

Conclusion: Daily CBCT–guided Plan-of-the-Day adaptive radiotherapy compensates for inter-fractional anatomical changes, has the potential to enable future reduced CTV-to-PTV margins. The PoD approach ensures target coverage while sparing bowel and bladder. Successful implementation depends on patient compliance with bladder-filling instructions, emphasizing the need for consistent pre-treatment preparation to maximize adaptive radiotherapy benefits.

Conflict of interests: The authors declare no conflict of interest.

Funding: This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.

License: ©️ Author(s) 2026. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, and unrestricted adaptation and reuse, including for commercial purposes, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

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