Frankincense essential oil is no more anti-cancer than many other essential oils. Frankincense resin, however, contains Boswellic acids which show broad anti-cancer and anti-inflammatory activity in the laboratory and have been used in traditional medicine for thousands of years.
The appearance of new medicine, mostly sourced from traditional ethnic pharmacopoeia, is driven by profit and not transparency. This has led to some inaccuracies and bits of misinformation that are conveniently geared to sell certain products. I will try to correct some of them here.