How long can you live with brain cancer that not be treated?

The life expectancy of someone with untreated brain cancer can vary widely depending on the type and location of the tumor, as well as the individual's overall health and age. Some types of brain cancer, such as glioblastoma, are very aggressive and can progress rapidly, leading to death within a few months to a year or so without treatment. Other types, such as meningioma, may grow more slowly and can sometimes be managed with supportive care for several years or even decades.

In general, the average survival time for people with untreated brain cancer is estimated to be around 3-6 months. However, it's important to note that this is just an average and there can be significant variation from person to person. Some individuals may survive for much longer, while others may pass away more quickly.

It is important to speak with a medical professional for a more accurate prognosis based on your specific circumstances and to discuss treatment options that may be available to you.