If by "heal" you mean "cure" breast cancer, the answer in none. Cannabis has never been shown to cure cancer in humans. It has been shown to kill some type of cancer cells in a laboratory. There have been stories by many people saying that they have been "cured" of various types of cancers using some type of cannabis oil or product. What cannabis has been shown to do is help with nausea from chemotherapy treatements and well as increasing appetite. That being said, there is most likely no harm in using cannabis along with whatever treatment your physician recommends. I would suggest telling then that you are using it as well.
Perry Solomon, MD
Although there are no large, controlled, scientific studies to show that cannabis heals cancer (and I doubt there ever will be), many people claimed to been healed using cannabis. Most likely, they also did other things like correct their diet, supplements, maybe ozone therapy, etc. Research "Rick Simptom Oil", it’s a potent cannabis oil, and doses that people state have healed their cancer is explained on various sites, such as this: http://phoenixtears.ca/dosage-information/ The instructions can be confusing, such as comparing doses to the size of a grain of short rice, but this is what I would use if I had cancer. My dog has cancer right now, so I’ve been researching all of this.
The HelloMD answer, from Dr. Solomon, is meant to legally protect the website from Federal authorities. A far more medically correct answer can be found here: http://www.canna-centers.com/ailments#Cancer
Possible anticancer actions of cannabinoids
THC increases the manufacturing of ceramide, which increases the possibility of cancer cell death
Prevents new blood vessels from growing into tumours
CBD shuts down gene responsible metastasis; stopping cells from moving or invading neighbouring tissue.
Most patients who are in countries where THC is restricted often resort to a whole plant cannabis extract that contains both CBD and CBDA. You can read more about CBDA research and breast cancer here https://www.ncbi.nlm.nih.gov/pubmed/27530354
The most common ratios is 1:1 or 1:3 CBD to THC
The cannabinoids will directly and indirectly affect your endocannabinoid system.
So the doctors are technically correct when they say that THC or CBD won’t "cure" cancer
What may happen is the cannabinoids can support your body and get it back into balance.