What bladder-filling protocol do you use when treating children with bladder neck rhabdomyosarcoma with definitive radiotherapy (VMAT)?

We have experiences from Proton beam therapy. Bladder filling protocol will depend on the tumor and age of the patient.

Our preferred way is to do it via suprapubic catheter if the tumor is not interfering with the position of the catheter. Filling volumes may be around 150-200 ml (however, the age/size of the patient to be considered). Sometimes we do it via IV infusion.

In older children (awake during PT), we may do it via drinking 30 minutes before the procedure. Volume, again, depending on the age/size of the patient and his/her capability to tolerate the filling volume.

For proton delivery in sedated children, we attempt to replicate the process at simulation and during treatment delivery with similar amounts of time elapsing between filling the bladder and CT sim imaging or proton delivery. We ask for IV fluids during sedation to run at a minimal rate. We calculate bladder capacity as follows:

{(age in yrs) + 2} * 30 = capacity in milliliters

We then instill half of this volume (usually with sterile water) after draining the bladder using a small age-appropriate Foley catheter. We plug/clamp the catheter for sim/delivery and then drain and remove after treatment each day. Sometimes, we have to adjust the initial fill volume depending on tumor volume.

For non-sedated patients, we ask them to void immediate...