Oncologists face ethical challenges when patients use potentially harmful complementary and alternative medicine in addition to or instead of conventional treatments for their cancer. For example, a patient may forgo effective cancer treatment in favor of alternative therapies and suffer significant harm as a result.L.R., a 65-year-old man, presents with recurrent colon cancer metastatic to liver and lung. L.R. was previously diagnosed with stage II sigmoid colon cancer, underwent resection, and postdischarge was monitored with surveillance alone. Three years later, L.R. has not attended surveillance appointments and returns to his primary care physician with complaints of fatigue and cough.

The National Center for Complementary and Integrative Health, a center of the National Institutes of Health, defines complementary health approaches as “practices and products of non-mainstream origin” and integrative health as “incorporating complementary approaches into mainstream health care.There are two major types of CAM: natural products (eg, herbs, vitamins, probiotics) and mind and body practices (eg, yoga, acupuncture, meditation). Additional practices, including traditional Chinese medicine and naturopathy, are less easily categorized but are also considered CAM.

So talking of those herbs is very much simple, but applying them is a harder job. 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6804900/