Overview of treatment options
The most important thing to consider when deciding on the best option for the person with brain mets is:
- performance status (SRS is only commissioned if WHO PS=0-2, less than this prognosis is very poor)
- extent/controllability of their extracranial disease (must be controllable for surgery/SRS)
- life expectancy (must be consider to be greater than 6 months for surgery/SRS)
- number, location, size and neurological effect of the metastases
The options for treatment of brain mets include:
- Stereotactic radiosurgery (SRS)
- Surgical resection
- whole brain radiotherapy
- systemic therapy
- best supportive care
SRS is high dose single fraction highly accurate radiotherapy. Doses are usually 15-24Gy (occasionally lower in highly eloquent areas (eg a large tumour in the brainstem). As a general rule the maximum size safely treated with srs is about 3cm in diameter. Multiple tumours (even >20 in rare cases where overall prognosis otherwise is good) can safely be treated in a single session as long as the total volume is <20cc. If treatment fails, then lesions can be retreated if >6 months post initial treatment (though surgery should also be considered). New metastatses (know as distant brain disease) can be treated with SRS- consider the “Brain Mets Velocity”- ie the number of new mets since original SRS per year. If <4/yr then prognosis is good so SRS, if >13 then poor so consider BSC (or WBRT) and in between prognosis is moderate, so the benefit of SRS might be modest.
If a tumour is >3cm surgical treatment can be best, but, if not operable, then large tumours (even those >10cc), can be treated with sterotactic radiotherapy. We use a regime of 10Gy every 2 weeks x3 (Total dose 30Gy- replanned every fraction which allows for shrinkage)
Surgery is ideal for solitary large tumours (in accessible sites) causing mass effect (including hydrocephalus). Post surgery, if there is any residual, give SRS to the cavity. If complete resection, then monitor closely with 3 monthly scans and treat if recurrence (likely in 60%). If one bulky tumour with mass effect needing surgery and some smaller ones, then after surgery we can treat all the others (and the cavity if feasible even if CR) with srs.
Whole brain radiotherapy is reserved for those with leptomeningeal disease and extensive mets. However, in these people, prognosis is poor, so BSC may be a better option, as WBRT will result in hair loss and significant fatigue.
Supportive care only, with steroids etc, may well be a better option for some patients with extensive disease or a very poor overall prognosis.
Teaching session from Dr Herbert on use of SRS in treatment of people with brain metastases, 2020. Video starts at 8min 30 sec