Final answer:
A craniotomy is the therapy required to open the skull and remove a tumor, which involves surgical removal compared to other non-invasive therapies like radiation or chemotherapy.
Step-by-step explanation:
The therapy that must be performed to open the skull and remove a tumor is known as a craniotomy. During this surgical procedure, neurosurgeons make an opening in the skull, which allows them to access and remove the tumor. This is in contrast to other therapies such as radiation therapy or chemotherapy, which do not involve making an opening in the skull but rather treat cancer through external or internal means, or electroconvulsive therapy, which is used to treat severe depression through electrically induced seizures.