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Dosimetrically triggered adaptive intensity modulated radiation therapy for cervical cancer
Karen Lim1, James Stewart2, Valerie Kelly3
1Department of Radiation Oncology, Liverpool Hospital, Sydney, Australia.
Summary
Adaptive radiation therapy for cervical cancer using a dosimetry-triggered approach ensures adequate target coverage, even with small margins. This method minimizes underdosing risk and reduces replanning workload compared to other strategies.
Area of Science:
- Radiation Oncology
- Medical Physics
- Gynecologic Oncology
Background:
- Intensity modulated radiation therapy (IMRT) for cervical cancer is challenged by internal target and normal tissue motion.
- Motion increases the risk of underdosing the target, especially with reduced planning margins aimed at lowering toxicity.
Purpose of the Study:
- To explore two adaptive strategies for mitigating underdosing risk in cervical cancer IMRT.
- To propose a novel, automated method minimizing replanning workload.
Main Methods:
- Prospective study of 30 cervical cancer patients undergoing IMRT with weekly MRI scans.
- Deformable image registration used to model accumulated dose under two adaptive replanning scenarios (anatomy-driven and dosimetry-triggered) with a 3 mm PTV margin.
Main Results:
- Without replanning, 27% of patients experienced target dose threshold failures with 3 mm margins.
- Anatomy-driven IMRT (A-IMRT) failed in 10% of patients (3/30) with 30 replans.
- Dosimetry-driven IMRT (D-IMRT) achieved adequate target coverage in all patients (0% failure) with 23 replans in 16 patients.
Conclusions:
- A dosimetry-triggered adaptive IMRT strategy effectively minimizes target underdosing in cervical cancer patients with interfractional motion.
- This novel approach ensures adequate target coverage while significantly reducing replanning workload and associated costs.
