Niaspan is just niacin, one of the B vitamins, and as far as I can tell,
is not cancerous in the dose given in
Niaspan. As
for your other question whether a five year study can demonstrate a drug-cancer connection, it would depend partly on the study design. The strength of the association between cause (the drug) and effect (cancer) would depend on how the evidence is gathered. Experimental studies (e.g.