Comparison of dose distribution for head and neck cancer patients with and without dose painting escalation during radiotherapy realized with tomotherapy unit.

OBJECTIVE

To determine and quantify the percentage dose increase to organs at risk (OARs) with multiple-level dose painting (DP) for patients with head and neck cancer in comparison with standard regimen.

METHODS

12 patients who had undergone fluorine-18 fludeoxyglucose (18F-FDG) positron emission tomography (PET)/CT scan were retrospectively enrolled. Two treatment plans-one using DP escalation and one without-were optimized for each patient base on PET/CT data. The following variables were assessed: dose to OARs and target volumes; execution time; equivalent uniform dose; and normal tissue complication probability.

RESULTS

No statistically significant differences in beam-on time were observed between plans with and without DP. However, significantly higher doses were observed for all DP-escalated plans in the OARs, with only two exceptions: the brain stem and V60Gy for the mandible. Multiple-level DP resulted in dose increases ranging from 3.0% to 12.9%, depending on the OAR. The largest increase was seen for the parotid glands and the smallest for the mandible. Significant differences in the equivalent uniform dose were observed only for the parotid glands and spinal column, where the dose without DP was lower. The normal tissue complication probability for most OARs was very small.

CONCLUSION

Importantly, even though DP escalation resulted in higher doses to OARs vs conventional treatment planning, these usually did not exceed the dose tolerance levels. However, clinical trials are necessary to confirm the benefits of DP and to guarantee no additional toxicity. Advances in knowledge: Multiple-level DP by numbers resulted in 3.0-12.9% dose increase, depending on the OAR. Our findings may suggest that DP escalation to very high doses is feasible for about 83% of patients without higher toxicity; however, it still should be confirmed on a larger group of patients.