Supine craniospinal irradiation in children: patient position modification, dose uniformity and early adverse effects

Different craniospinal irradiation techniques are complex. The homogeneity of the dose to the target and the normal tissues at risk affect both the control rate and the level of adverse effects.

Thirty one patients were treated with CSI in the supine position. Custom-made Styrofoam was tailored for each patient to straighten the convexity and concavity of the spinal axis allowing better dose distribution uniformity during CSI technique. In the first 6 patients, CT simulation were performed twice: one time with the patient lying directly on the vacuum mattress without the foam (the conventional way) and the second while lying on the foam. Dose distribution was calculated using a 3D conformal planning. The gap between the fields was determined using isodose alignment method. All treatment portals were verified during the first 3 treatment sessions and once weekly thereafter using either cone-beam or portal image device. Weekly feathering (shifting of the junction between the 2 adjacent radiation fields) was routinely performed.

The 95% dose distribution had better coverage with the foam (p=0.042) while the hot volume of 110% and 105% dosage were significantly lesser than conventional technique (both p=0.028). The organs at risk received nearly similar radiation doses in the 2 positions. The CSI led to minimal immediate adverse effects that were reversible. Weight loss was experienced by 55% of patients.

This modified technique of CSI is simple, ensuring better dose distribution to CSI target without increasing the dose to the surrounding organs at risk. It is tolerable and safe to apply.