HELP! Mom diagnosed with leptomeningeal disease after one year on Tagrisso.

My mom has been on her second line treatment, Tagrisso, for over a year. Recently we got a PET/CT scan and a MRI. The PET/CT showed mostly stable disease but two lymph nodes and a bone spot that are showing activity again. The MRI (brain scan) showed 3 suspicious lesions which will be radiated with cyberkife. The problem is, the MRI also showed early signs of leptomeningeal disease (LMD). Obviously this is a very serious situation. Since my mom already had whole brain radiation two years ago, it is not an option. Cyberknife is also not an option for LMD either. Our oncologist is suggesting doubling her dose of Tagrisso from 80mg to 160mg but I am skeptical of this method. She's been on Tagrisso for over a year and up to this point, it has been holding things in the brain at bay. I don't see how doubling it will suddenly make it more effective.

I've read studies and heard of people adding Avastin (bevacizumab) to Tagrisso when LMD shows at progression. This approach makes more sense to me. However, I was hoping to find people on this thread who have been on Tagrisso 80mg then doubled it at the sign of brain progression to 160mg and had success. I know many people have taken 160mg as their starting dose because they had LMD prior to starting Tagrisso, but I am hoping to find people on here who have tried doubling it at the sign of LMD after having success on a normal 80mg. Would also love to hear from people who tried adding Avastin or doing some other therapy that helped them. Thank you!