The Oncology Association of Naturopathic Physicians (OncANP) annual conference was chock-full of excellent talks on the use of a variety of supplements that may be useful in helping to reduce the risk of cancer development, progression and recurrence.
I wrote a blog post, yesterday, on Dr Dugald Seely’s talk on the use of melatonin supplementation in cancer treatment.
Today, I will update you on the latest information on Metformin.
Metformin is a medication derived from the herb Galega officinalis, also known as French lilac. (Also check out my previous blog article on Metformin.)
Metformin
The talk on metformin was given by Dr Davis Lamson, MS, ND (Tahoma Clinic and Bastyr University.) He made a compelling case for why this commonly prescribed, inexpensive (and safe) diabetes medication might want to be added to the care plan for patients with any one of a variety of cancer types.
First of all, metformin has been used for over 50 years in the management of diabetes. So, we have lots of safety information on it. It is also available as a generic prescription, so it’s relatively cheap. The challenge for many patients who might want to use it is that most physicians will not write a prescription for it unless you have diabetes (as metformin is only approved by the FDA for this indication.) You might ask your physician to read this article to help convince them to prescribe it to you.
Metformin is such a promising anti-cancer medication that there are approximately 150 clinical trials (see ClinicalTrials.Gov) investigating its’ use in cancer treatment and prevention.
How does it work?
Cancer loves sugar (see our blog post on this here.) So, if you reduce the amount of sugar available to feed cancer cells you will significantly slow their growth. Metformin reduces blood sugar through a few different mechanisms: 1) decreasing the amount of sugar made by the liver, 2) reduces the absorption of sugar from the intestines, 3) increases insulin uptake into healthy cells (decreasing sugar in the blood.)
Metformin does all this by activating an enzyme called AMPK (AMP-activated protein kinase), which plays an important role in insulin signaling, systemic energy balance, and the metabolism of glucose and fats. Activated AMPK slows cancer growth by:
- reducing the amount of sugar available for cancer cells to consume (by lowering sugar output from the liver, increasing sugar uptake from the blood, and maintaining insulin sensitivity)
- inhibiting an enzyme called mTOR (mammalian target of rapamycin), which is responsible for cell growth…including tumor cell growth!
Metformin can also inhibit mTOR directly (independent of AMPK activation), slowing tumor growth.
Metformin also kills cancer stem cells, often the most resistant (to both chemotherapy and radiation therapy) cell type in tumors.
Metformin seems to also prevent precancerous cells from evolving into cancer cells.
Metformin reduces the amount of circulating estrogen and testosterone, both of which can stimulate the growth of hormone-dependant tumors (i.e. breast cancer, prostate cancer)
Human Studies Show Improved Outcomes On Metformin:
One of the most compelling studies that I have seen on the use of metformin’s anti-cancer activity comes from an analysis of 8,000 patients with type 2 diabetes who were followed for 10 years. The researcher found that there was a 54% lower risk of developing any type of cancer among those taking metformin compared with those not taking metformin. (study)
Here are some of the data on specific cancer types that Dr. Lamson presented to us at the conference:
Breast cancer:
- Response rate to neoadjuvant chemotherapy (this means, chemotherapy given before surgery to shrink the size of the tumor): among a group of patients with type 2 diabetes, those taking metformin had a 24% chance of having a complete response (this means, no residual cancer found during surgery) versus only an 8% chance of having a complete response if not taking metformin. (study)
Colorectal cancer:
- Risk of developing colorectal cancer: 200% greater for those with type 2 diabetes who were not taking metformin versus those taking metformin. (study)
- Survival: 34% greater for those with type 2 diabetes who were taking metformin versus those not taking metformin. (study)
Lung cancer (non-small cell cancer):
- Survival after chemotherapy: Type 2 diabetics taking metformin had an overall survival rate of 20 months (and a progression free survival of 8.4 months) versus 13 months (and a progression free survival rate of 6.4 months) for type 2 diabetics not taking metformin. (study)
Ovarian cancer:
- Survival and recurrence after chemotherapy: among a group of patients with type 2 diabetes, those who used metformin had a 5 year overall survival rate of 63% versus only 23% in those patients not taking metformin; progression free survival at 5 years (meaning, the chance of being alive at 5 years with no evidence of cancer) was 51% in those taking metformin and 8% in those not taking metformin. (study)
Prostate cancer:
- Risk of developing prostate cancer: there was no risk reduction seen among type 2 diabetics taking metformin compared with those not taking metformin. (study)
- Survival: Overall survival rate was 45% greater in type 2 diabetics taking metformin versus those not taking metformin. (study)
- Survival: Another study found that metformin use improved survival by 24%. (study)
Anti-Cancer Activity of Metformin Has Been Reported In Many Cancer Types (in Preclinical and/or Clinical Studies):
- breast cancer
- colon cancer
- endometrial cancer
- glioma (brain tumor)
- hepatocellular cancer (liver tumor)
- leukemias (ALL, AML, CML)
- lung cancer (non-small cell cancer)
- lymphoma (B-cell)
- melanoma
- ovarian cancer
- pancreatic cancer
- prostate cancer
Dosing:
500 mg (taken two to four times per day)
Safety of Metformin:
Considered very safe, but there are potential risks.
- If you have renal failure, you should not take metformin due to the risk of lactic acidosis.
- Gastrointestinal upset in 30% of patients (much less common when taken in the extended-release form of metformin)
- Hypoglycemia: very rare
- Malabsorption of vitamin B12 occurs in up to 30% of patients (check vitamin B12 levels once to twice per year)
- May cause thyroid hormone abnormalities (check thyroid hormone levels once to twice per year)
- May reduce testosterone levels (check once to twice per year)
Read more about potential side effects (Drugs.com)
Read more about potential drug-drug interactions (Drugs.com)
Bottom Line:
Metformin is a promising plant-derived compound that has significant anti-cancer activity (reducing the risk of cancer development, cancer recurrence and progression) for many cancer types. The risks are low and it’s inexpensive (only $0.50-$1.00 per day)…but you may have a hard time convincing your physician to give you a prescription for it if you don’t have type 2 diabetes.
Certainly, if you have type 2 diabetes (and even if you don’t, but are overweight) it’s worth having a discussion about the use of metformin (preventively or therapeutically) with your physician.
