(HealthDay)—The combination pill Lonsurf (trifluridine and tipiracil) has been approved by the U.S. Food and Drug Administration to treat advanced colon cancer for people who aren't responding to other treatments, the agency said Tuesday in a news release.

Colon cancer is the third most common cause of non-skin cancer in the United States, the FDA said, citing the U.S. National Cancer Institute. It's still the second most common cause of cancer death behind , although rates have been declining, in part, due to increased screening for the disease.

Lonsurf was evaluated in clinical trials involving some 800 people with previously treated advanced colorectal cancer. Those who took Lonsurf lived an average of more than 7 months, compared to 5.3 months for those who took a placebo.

The drug's most common side effects include anemia, a drop in infection-fighting white blood cells, a drop in , weakness, fatigue, nausea, loss of appetite, diarrhea, abdominal pain and fever.

Due to the potential for a severe drop in blood cell and platelet production, doctors are urged to test users' blood before the start of each treatment cycle, the FDA said. Doctors also are advised to warn women of childbearing age of potential harm to developing fetuses. And women who use Lonsurf should not breastfeed, the agency warned.

Lonsurf is produced by Princeton, N.J.-based Taiho Oncology.

More information: The FDA has more about this approval.