Dosages vary by protocol, but most are based on your child’s weight or body surface area (BSA). BSA is calculated from your child’s weight and height, and it is measured in meters squared (m²). Your child’s doses should be recalculated by the doctor at the start of each new phase of treatment. If your child has significant weight gain or loss (more than 10% of initial weight), more frequent recalculating of doses will be needed.

My son’s protocol required that his height and weight be measured each time chemotherapy was to start. When we would arrive in the clinic, the nurses would take his measurements, then calculate his body surface area using those figures. His weight fluctuated considerably over the course of his treatment, so the actual dosage of the drugs that he received was never quite the same.

You don’t need to do the calculations, but it is important to know the right dosage for each drug given at home and how you should give it to your child. Most families write the dosages on a calendar and cross them out after each dose has been given to make sure they don’t forget a drug or accidentally repeat a dose.