A topic not always discussed is the use of terpenes in disease. There have been studies and reports of terpenes having cancer preventive effects.
Monoterpenes (the simplest of the terpenes) are of low molecular weight and are the primary components of essential oils. The potential anticancer actions of monoterpenes include: induce apoptosis, induce differentiation, and inhibit tumor induced immunosuppression. One of these essential oils is limonene, the primary constituent of orange oil. It has been extensively studied at the University of Wisconsin. It has been shown to hinder the following cancers: stomach, lung, skin and liver cancers. This was done in rodent models.
The perfume industry has a better limonene called perillyl alcohol. It is more potent than limonene, inducing tumor regression 5-10 times more in breast cancer in rats.
I find from all my reading and research that there are many natural compounds used in cancer therapy.