Impact of Geometric Uncertainties on Dose Distribution in Head-and-Neck Cancer Radiotherapy
Author Information
Author(s): Ballivy O., Parker W., Vuong T., Shenouda G., Patrocinio H.
Primary Institution: McGill University
Hypothesis
How do geometric uncertainties affect dose distribution during intensity-modulated radiotherapy for head-and-neck cancer?
Conclusion
Adding localization uncertainty margins during treatment planning significantly reduces the risk of underdosing targets and overdosing critical structures.
Supporting Evidence
- Only 12.5% of gross tumor volumes had adequate target coverage without margins.
- Using 2.5-mm and 5.0-mm margins improved target coverage significantly.
- The mean dose to the contralateral parotid increased with larger margins.
- 57.7% of cases exceeded the maximum dose limit for the spinal cord without margins.
Takeaway
This study shows that when treating head-and-neck cancer, it's important to add extra space around the target area to make sure the right amount of radiation reaches the tumor without harming nearby organs.
Methodology
The study involved generating intensity-modulated radiotherapy plans with different localization uncertainty margins and recalculating dose distributions based on repeat CT scans during treatment.
Limitations
The study did not assess mechanical uncertainties inherent to treatment delivery and had a relatively low number of repeat CT scans per patient.
Participant Demographics
Patients included 4 with oropharynx cancer, 2 with nasopharynx cancer, 1 with maxillary sinus cancer, and 1 with nodal metastasis, all with locally advanced stage III-IV disease.
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