Oncology (General Cancer)/Preventative Radiation to the Brain
My mom (77 years old) completed chemo for SCLC at the end of November. She responded very well. Her radiation oncologist suggested preventative radiation to the brain. She had an MRI a few weeks ago and he said it is clear. I've been reading quite a bit regarding the side effects and my biggest concern is dementia. It seems like it's 50/50 as to whether she will end up with cancer in her brain, so we have having a difficult time deciding if we should go through with this. What are the most common side effects and what are the odds she will end up with dementia? Thank you.
We do know that radiation to the brain improves survival and reduces the likelihood of brain metastases. We also know that radiation can hasten the onset of dementia. So you are right, it's a difficult question. Dementia is dose related and related to the size of the dose as well. The statistics suggest that about 5% of patients who receive doses in the range of 3000 rads will exhibit severe dementia during the next few years. There is some evidence that giving smaller doses over a longer period of time may reduce that risk. Oxygenation, antioxidants, and some drugs may protect the brain, and you might want to talk to your oncologist about the latter. The likelihood of her getting recurrent brain mets in the next year, however, is quite a bit higher than her getting severe dementia in that time frame. Some estimate that without radiation brain mets might occur in up to 1/3 of patients like her, without radiation. So the trade-off is clear to me -- better the radiation and the risk of dementia than the risk of recurrence. You could take your chances with recurrence and give her radiation if that happens, but that is much more likely to cause dementia, and would not increase her chances of cure.
Of course at the age of 77 cognitive decline is likely anyway over the next few years.
I'd be in favor of the brain irradiation, possibly giving it in lower doses over a longer time.