It sounds like a really bad idea for a Stage IV cancer patient to fast. In later stages they frequently already have substantial weight loss... and in the last few weeks, people actually stop eating entirely as the body starts to shutdown. Death usually occurs when the weight loss reaches 30-40%.
Encouraging them to stop eating seems like it would just accelerate death.
I just went through 6 cycles of 5-day IV chemotherapy (AIM) and I fasted for all of them, for a total of over 35 days of water-only fasting during the last 5 months. I can’t find the PubMed link right now but there were small studies that looked like healthy cells would go into kind of a suspend/preserve mode that lessened side effects, whereas cancer cells still experienced the intended cytotoxicity. I tolerated the treatments quite well, lost hair of course but only vomited twice during the whole time. Lost weight each time but was able to put it back on quickly during the following week for each cycle, though I do want to watch body composition (don’t want to trade muscle for fat).
Did it make a difference in effectiveness? I actually have my follow up scans tomorrow to find out. As you can imagine, I really really hope so.
I'm not a doctor. Ive just spent a lot of time looking into this (as im sure you have) because a close relative died from Stage IV lung cancer.
There are studies on fasting with chemo.. and depending on the type of cancer its either effective or ineffective. My comment was specifically about the end stages where cachexia is common (from my link above):
"Cachexia is associated particularly with cancer where the prevalence can reach 50–80% in advanced malignant cancer."
And all of the advice Ive found says fasting is not recommended for patients with cachexia.
It sounds like it was fine in your case though because you were able to regain the weight. Best of luck with your scans.
Encouraging them to stop eating seems like it would just accelerate death.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5114624/