''A 2006 systematic review by the Cochrane Collaboration concluded: "The claim that [l]aetrile has beneficial effects for cancer patients is not supported by data from controlled clinical trials. This systematic review has clearly identified the need for randomised or controlled clinical trials assessing the effectiveness of [l]aetrile or amygdalin for cancer treatment." Given the lack of evidence, laetrile has not been approved by the U.S. Food and Drug Administration. The U.S. National Institutes of Health evaluated the evidence separately and concluded that clinical trials of amgydalin showed little or no effect against cancer. For example, a 1982 trial of 178 patients found that tumor size had increased in all patients. The authors reported that "the hazards of amygdalin therapy were evidenced in several patients by symptoms of cyanide toxicity or by blood cyanide levels approaching the lethal range".''
http://en.wikipedia.org/wiki/Vitamin_B17 for references 5, 9, 13, 25.
About the interactions, well, it depends on the enzymes acting to metabolize the medications in use and some other factors.
Vitamin B17 should not be considered a vitamin just like vitamin D as both are not vitamins. Glycosides and secosteroids being vitamins? What?
The wise thing to do is to follow the doctor's indications as he is the one who knows the current stage of his cancer, patients blood counts etc.
I am not saying that crunching some apricot kernels here and there is not safe and not healthy but special precautions need to be considered with patients undergoing chemotherapy treatments.
You might want to contact American Biologics about this. They sell apricot kernels, and also run an alternative medicine hospital. They would know of any contraindications with the chemo, I would think. But just crunching a few is pretty useless even assuming there was any solid evidence laetrile worked -- they haven't even isolated the laetrile, so you're not getting very much. You have to take a lot for it to work, assuming it works at all.