Carcinoid Tumors

[NanaJo]

Greetings. I am new to this site. My first husband died of carcinoid syndrome, after living with the disease for 17 years. His was gastrointestinal with metastases to the liver when diagnosed. Currently, I'm an instructor with The Cancer Project in D.C., and do Food for Life Nutrition and Cooking classes for cancer prevention & survival. I know the link between nutrition and cancer; it's well documented.
My concern is for my 2 adult children. My husband's sister was diagnosed with exactly the same carcinoid during my husband's last 6 months of life. That was five years ago. She is still in treatment. When that happened I became very concerned. My husband's doctor said this cancer wasn't genetic, but I research different assessments - that genetics plays a role.
I also know that predisposition to certain genes doesn't mean that gene will be expressed. Since animal protein and high fat diets raise hormone levels in our bodies, and that's a risk for cancer, is there any info out there re carcinoid and plant based nutrition?
Any feedback would be appreciated.