Combining avoidance structure and jaw-tracking techniques to reduce the dose to lens in radiotherapy for sinonasal cancer

Purpose

To assess the effectiveness of avoidance structure (AS) techniques, alone and in combination with jaw-tracking (JT) techniques, in the treatment of sinonasal cancer, with the aim of minimizing radiation exposure to the lens.

Methods

Thirty patients were included in the study, and three sets of intensity-modulated radiation therapy (IMRT) plans were designed in an Eclipse treatment planning system: (1) original plans (O-Ps) with seven non-coplanar fields were optimized to meet clinical criteria; (2) duplicated O-Ps were re-optimized using the AS technique (AS-P), specifically for lens structures while keeping other optimization conditions consistent; and (3) utilizing both AS and JT techniques to generate a third set of plans (AS-JT-P). Dosimetric parameters, including dose to target volume and organs at risk (OARs), were evaluated. Additionally, the Lyman—Kutcher—Burman (LKB) model was utilized to predict the normal tissue complication probability (NTCP) of OARs. The data from three sets of treatment plans were collected and compared.

Results

Compared to O-P, the average reduction of D_2% for the lens in AS-JT-P was approximately 2-3 Gy, with a corresponding average NTCP reduction of 0.1-0.3%. The AS-P reduced the D_2% of the contralateral lens by approximately 1Gy. The differences mentioned above were statistically significant (P<0.05). Additionally, the AS technique resulted in a slight deterioration in dose uniformity and conformity for the target volume, with minimal impact on other OARs.

Conclusions

The combination of AS and JT techniques can effectively minimize the radiation exposure to the lenses, reducing the risk of radiation-induced cataract. The use of AS and JT techniques is recommended in clinical practice for the treatment of sinonasal cancer.