Today the Internet is full of news about a new drug called dapagliflozin, for Diabetes. The results of a two year study were presented to the public by the makers of the new drug -- Bristol-Meyers and Astra-Zeneca.
Reuters (1) had a very brief news bulletin saying dapagliflozin is effective “but the companies said more bladder and breast cancers have been seen in patients treated with the drug.”
Medical News Today (2) wrote a more detailed article saying that the two year study demonstrated that dapagliflozin was effective but there were nine cases of bladder cancer and nine cases of breast cancer in the treatment group as opposed to one case of bladder cancer and one case of breast cancer in the control group. The article stated the "Elisabeth Svanberg, the vice president of development for Bristol-Myers, believes the difference in cancer risk is most likely "a numerical imbalance. Those occur in clinical trials.""
The press release from Bristol-Meyers and Astra-Zeneca (3) was widely circulated by the news media. The San Francisco Chronicle (4) said, “A two-year study of Bristol-Myers Squibb Co.'s and Astra-Zeneca Inc.'s experimental diabetes pill dapagliflozin showed it was safe and effective.”
Bloomberg (5) was a little more objective. It said that two years long study showed that the drug was effective but had more breast and bladder cancer than on standard drugs.
It is hard to look at the headlines and figure out what is going on. They say there were nine cased of bladder cancer and nine cases of breast cancer in the treatment group and only one case of bladder cancer and one case of breast cancer in placebo group. Then they say that the drug is safe and effective!
A detailed study of the literature shows that there is element of truth in both. (The literature is all provided by the drug company since there is no independent research on this drug.) The two year study showed that the drug was modestly more effective than the standard drugs. The study group had more bladder and genital infections than the standard group. So far the company has data on 5,748 patients on dapagliflozin and 3,156 on the standard drug (glipizide). There have been nine cases each of bladder cancer and breast cancer in dapagliflozin and one of each in glipizide group. The drug company believes that this is just a coincidence.
I personally believe that we should be very careful to introduce an entirely new class of drug into the treatment regime unless the drug is unequivocally effective and safe. Dapagliflozin is only modestly more effective than glipizide. Dapagliflozin acts by increasing the sugar output in the urine. No other drug does that. The increased sugar in the urine causes increased infections in the short term but we do not know how it will affect the bladder and kidneys in the long term. Diabetes is a lifelong condition. What will happen to the kidney, ureter, and bladder epithelium after ten years of exposure to high levels of glucose is not known at the present time.
I am going to withhold judgement till more data is available, preferably from clinical studies that are not sponsored by the drug companies. There is no hurry to use this drug. It is not a whole lot more effective than the drugs that have safety data from over thirty years of use.