I’m glad that you have recovered :)

Honestly, I’m not very familiar with the cancer literature. But a brief search shows me this review paper where studies have detected reduced brain volume in the hippocampus, although there might also be other affected brain areas.

(https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4750385/)

Hippocampus is responsible for most of the human memory, especially factual memory. Among all the brain areas, the hippocampus has the greatest expression of glucocorticoid receptors that respond to cortisol, the stress hormone. So, it makes sense that diseases that inflict stress on the body would likely affect the hippocampus.