How does THC attack cancer

Blog: Knowledge Against Cancer

Welcome to the second part of our current blog topic cannabidiol (CBD).

As we saw last week, CBD is one of the many components (cannabinoids) in cannabis, the potential effects and medical uses of which are currently being intensively researched. In doing so, we've shown how CBD is cautiously entering the neurology and mental health areas in particular, and that it may still have a respectable medical career ahead of it.

We had saved the cancer area, which is so important for this blog. This is what we will focus on in this second part.

CBD and tumor diseases: legitimate hope for help?

If you believe the relevant Google search results, CBD is a serious candidate, not only to alleviate the side effects of a tumor disease such as pain and weight loss, but also to attack tumor tissue. Positive reports about CBD for cancer do indeed give rise to hope, especially when such statements are linked to a scientific publication (1, clinical study).

For the sake of clarity, we want to divide the discussion of the topic of CBD and cancer into three areas: 1. Basic research, 2. Combating cancer with CBD (based on study results on patients) and 3. Concomitant therapy to alleviate disease symptoms.

1. Basic research: For a long time it has been known from laboratory tests that, in addition to its anti-inflammatory and antioxidant properties, CBD can also have a direct negative impact on the expansion and spread of tumor cells. Here, CBD apparently acts extremely selectively, i.e. it attacks tumor cells and spares healthy cells in the process. In addition, the aforementioned antioxidant abilities of the CBD also play a role in cancer inhibition (2, laboratory study).
Current study results confirm what is often reported by CBD practitioners and users, namely that the effect of cannabis depends on the composition, the dosage and the time of administration: Leukemia cells are indeed inhibited by individual substances from the cannabis plant (e.g. CBD) ; in combination (e.g. CBD and THC), however, the effect is even more effective. In addition, it may be better to give them after a single dose of chemotherapy to increase the effectiveness of the treatment (3, laboratory study). It can also be advantageous not to take CBD continuously, but at intervals (1 and 4, laboratory study).

2. On the patient: Unfortunately, the findings mentioned under point 1 cannot simply be transferred to the effects on humans. Its organism is too complex for this. In addition, there is not a single study published in reputable databases in which, in a sufficiently large number of affected patients, CBD as an anti-tumor therapeutic agent was compared with the established cancer treatment or with a sham medication. Rumors are circulating on the Internet about a (very questionable) individual report on a possible CBD effect against a subtype of skin cancer. An original paper cannot be found (5, allegedly clinical study). In contrast, the publication mentioned at the beginning (1, clinical study) is somewhat more informative. 119 patients with mostly advanced tumor disease were analyzed after treatment in the form of an objective tumor reduction using (mainly synthetic) CBD. Of the 119 patients, however, only 28 received only CBD. According to the authors, there have been some spectacular improvements, especially in breast cancer patients or in the neuro-oncological field. The extent to which these are due to the sole effect of the CBD cannot be proven. Still, such patient histories are very useful in motivating future studies.

3. In accompanying therapy: As a result of the as yet unclear immediate cancer-inhibiting effect, CBD is currently mainly used against (partly therapy-related) accompanying symptoms such as fears, sleep disorders, nausea or pain (see last week's blog post). Unfortunately, even these indications are based almost exclusively on results from laboratory tests. In addition, research publications do not always clearly separate whether the CBD was not also accompanied by THC (see above). THC, which can reduce nausea, pain and loss of appetite in particular, is possibly the more important element of the two cannabinoids CBD and THC in these cases. For cancer patients who are treated with paclitaxel (or other nerve-damaging substances), CBD could be of interest to prevent the so-called chemotherapy-induced polyneuropathy (CIPN), which is noticeable in pain, numbness and tingling sensations (6, laboratory study).

Is there anything wrong with CBD?
If the benefits of a substance like CBD have not yet been clearly established, at least taking it shouldn't hurt. In this regard, there seems to be little concern with CBD. Except for extreme doses, CBD should be well tolerated by most people (7, laboratory studies and clinical data), although significantly higher doses can be tolerated if it is taken for a short time (8, clinical studies).
However, possible interactions with drugs such as warfarin or diclofenac are more problematic (8). It has not yet been clarified to what extent these play a relevant role in everyday therapy, or whether interactions with cancer drugs must also be taken into account.

Product choice and dosage
Rule 1:
only seek out trustworthy information, counselors or practitioners.

Rule 2: only choose CBD products in pharmacy quality. At least the manufacturer should follow the criteria of “Good Manufacturing Practice” (GMP, 9) and guarantee organic quality as far as possible.

Rule 3: there is (still) no absolute rule as to how and how high the dose of CBD should be. In the observational study of 2018 (1), dosages between 5 and 30 mg daily are described. In individual studies, however, much higher doses up to a maximum of 1500 mg daily were used (8). However, such amounts should never be taken outside of studies. In addition, it seems to make sense to dose at intervals: 3 days intake, 3 days break (1). Such a regime corresponds to the naturopathic basic approach of the "stimulus-response principle" (10, textbook).

Legal issues
The legal situation of cannabidiol-containing products such as oils that are absorbed through the oral mucosa or capsules is somewhat confused: On October 1, 2016, CBD was added to Appendix 1 of the Medicinal Prescription Ordinance (11). With this decision, a statutory prescription requirement for CBD applies, whereby an (unlimited) transition period has been granted. So far, CBD with a maximum of 0.2% THC was one of the dietary supplements in Germany. And in fact, to this day, CBD oil is sold freely without a prescription, without this having led to any difficulties for manufacturers, retailers or the consumer. The condition is that no promises of salvation are made or may be made in the advertising and description of the products. Nevertheless, doctors can or should prescribe oils containing CBD, but this does not automatically mean that the costs are covered by the statutory health insurance companies. However, applications for reimbursement of costs to the health insurance company may be approved.


With regard to the use of CBD in the context of a tumor disease, the findings are still mainly based on the results of basic research (cancer cell lines and animal models). These research results are undeniably very interesting and call for large, controlled clinical studies. It remains to be seen whether affected patients want to wait for it.

So far, some types of tumor have emerged that are more sensitive to CBD than others and should preferably be examined in cancer patients: breast cancer, glioblastoma, leukemia / lymphoma, lung cancer and colon cancer.

Since CBD is usually well tolerated with careful individual dosing, it is understandable that individual cancer patients resort to a CBD oil, for example. However, the intake should always be guided by a well-informed and experienced practitioner.


[1] Kenyon et al. Report of Objective Clinical Responses of Cancer Patients to Pharmaceutical-grade Synthetic Cannabidiol. Anticancer Res. 2018 Oct; 38 (10): 5831-5835. doi: 10.21873 / anticanres.12924.

[2] Massi P, Solinas M, Cinquina V, Parolaro D. Cannabidiol as a potential anticancer drug. Br J Clin Pharmacol. 2012; 75 (2): 303-12.

[3] Scott KA et al. Anticancer effects of phytocannabinoids used with chemotherapy in leukaemia cells can be improved by altering the sequence of their administration.Int J Oncol. 2017 Jul; 51 (1): 369-377. doi: 10.3892 / ijo.2017.4022. Epub 2017 May 29.

[4] Scott KA et al. Enhancing theactivity of cannabidiol and other cannabinoids in vitro through modifications to drug combinations and treatment schedules. Anticancer Res 33: 4373-4380, 2013.

[5] Physician’s documentation confirms successful treatment of basal cell carcinoma resulted from the application of a topical cannabis extract. Cannabis Science, 2011

[6] Ward SJ, McAllister SD, Kawamura R, Murase R, Neelakantan H, Walker EA. Cannabidiol inhibits paclitaxel-induced neuropathic pain through 5-HT (1A) receptors without diminishing nervous system function or chemotherapy efficacy. Br J Pharmacol. 2014; 171 (3): 636-45.

[7] Bergamaschi MM, Queiroz RH, Zuardi AW, et al. Safety and side effects of cannabidiol, a Cannabis sativa constituent. Curr Drug Saf. 2011; 6: 237-249

[8] Iffland K, Grotenhermen F. An Update on Safety and Side Effects of Cannabidiol: A Review of Clinical Data and Relevant Animal Studies. Cannabis Cannabinoid Res. 2017; 2 (1): 139-154. Published 2017 Jun 1. doi: 10.1089 / can.2016.0034

[9] Good Manufacturing Practice, (accessed 12.01.2019)

[10] Dieter Melchart and Rainer Brenke. Naturopathic treatment: guidelines for medical training, further education and training, Schattauer Verlag, September 2007

[11] Article 1 - Fifteenth ordinance amending the Medicinal Prescription Ordinance (15th AMVVÄndV n.a.Abk.), V. v. 09/27/2016 Federal Law Gazette I p. 2178 (No. 46); Valid from October 1st, 2016

About Wolfgang Doerfler

Wolfgang Doerfler heads the advice center for complementary medicine and naturopathy at the Munich Tumor Center. He writes blog posts on science-based naturopathy and lifestyle medicine.