Medulloblastoma (WHO grade IV)

My brother(29 years) has been battling medulloblastoma (WHO grade IV) for almost five years. During this time, he has undergone extensive treatment including multiple surgeries, craniospinal radiotherapy, several lines of chemotherapy, SRS/FSRT, and systemic therapies such as temozolomide, irinotecan, and bevacizumab.

Due to the development of hydrocephalus, a ventriculoperitoneal shunt (brain pump) was implanted four months ago, which has helped manage intracranial pressure.

He is currently facing disease progression, confirmed by recent MRI findings. At the moment, he is waiting for genetic blood analysis to be performed in Zagreb, but the timing is uncertain and may take additional weeks.

In parallel, we have contacted the Heidelberg oncology/neuro-oncology center for a second opinion and possible treatment options and are currently awaiting their response.

Given the long disease course, recent progression, and overall clinical situation, our family is concerned that waiting for genetic test results may delay potentially beneficial treatment.

We would appreciate guidance on the following:
• In cases like this, is it medically reasonable to start treatment without waiting for genetic blood analysis results?
• How critical are genetic blood tests for determining the next line of therapy in recurrent medulloblastoma?
• Can treatment be adjusted later once genetic results become available?
• Does anyone here have experience with the Heidelberg center in similar neuro-oncological cases?

Any advice on how to balance the urgency of treatment versus waiting for additional diagnostics would be greatly appreciated.