I have looked at scientific support for nearly all the major herbs used in Ayurveda and Traditional Chinese Medicine formulations for cancer treatment. Many a molecule used in modern medicine today for the treatment of cancers has a herbal origin.
Herbs are often a base for foundational scientific research to test the efficacy of molecules that may promise cancer treatment. Most of these molecules are tested up to the animal trials stage. If they demonstrate scientific promise, the molecules move to drug discovery teams for further human clinical trials.
The evidence on most herbal medicine anti-cancer formulations is tenuous. There are, though, some molecules that hold promise. I am presenting a preview of some of this work below:
Turmeric (curcumin), red chili (capsaicin), cloves (eugenol), ginger (zerumbone), fennel (anethole), kokum (gambogic acid), fenugreek (diosgenin), black cumin (thymoquinone) contain chemicals—shown in the bracket after each herb—that prevent cancer (Aggarwal et al., 2008).
Broccoli and other cruciferous vegetables are observed to reduce cancer risk in organs such as colorectum, lung, prostate, and breast. This protection is attributed to the high amount of glucosinolates molecules found in such vegetables (Abdull et al., 2013).
Numerous scientific studies have shown that consuming fruits and vegetables may help significantly reduce cancer incidence. Other cancer-preventive molecules identified as chemopreventive include isothiocyanate, genistein, epigallocatechin gallate, lycopene, and resveratrol. The molecules are found in select herbs, fruits, and vegetables. (Russo et al., 2010).
While phytochemicals, which are nonnutritive chemicals found in plants and food, modulate cell signals and cause anticancer effects, the challenge is to develop personalized supplements of specific phytochemicals for each clinical situation (González-Vallinas et al., 2013).
This is the emerging frontier of cancer-preventive research. Anticarcinogenic action is caused by phytochemicals impeding intracellular signals that trigger cancer (Surh, 2003).
In summary, herbal medicine does not have a cure for cancer. Its role is, at best, supportive. There are molecules found in herbs that hold promise for discovering anticancer medicine.