D-Mannose, as you probably know is a sugar closely related to glucose It is found in high concentrations in fruits such as cranberries. It is sold as a supplement since many people think it helps with UTIs by interfering with the growth of e coli. There are some recent studies and especially a January 2024 study done in China which Indicate oral administration of D-mannose dramatically inhibited angiogenesis and tumor growth in mice. Their findings reveal a previously unrecognized anti-tumor mechanism of D-mannose by destabilizing VEGFR2. This is a growth factor which cancers use to spread by creating new blood vessels. However these studies were only done in cell culture and in mice, I have not been able to find any published human studies. Taking this as a supplement probably won't hurt. The problem is you don't know the maximum amount you could take without it being a safety issue. Suggest you talk to your oncologist and ask the maximum amount of supplement can recommend