Doctors appear to have safely and successfully treated patients with cancer of the blood and bone marrow with a combination of arsenic and vitamin A, according to long-term study in China.

In an article published in the Proceedings of the National Academy of Sciences, the doctors said they prescribed the regimen to 85 patients and monitored them for an average of 70 months.

Of these, 80 patients went into complete remission and the researchers did not find any associated long-term problems in their heart or lungs and there was no development of secondary cancers.

“Two years after their treatment, the patients had arsenic blood and urine levels well below safety limits, and only slightly higher than controls,” they wrote.

“The treatment was effective … and worked better than either drug given alone.”

The authors recommended that the treatment be given to patients with blood and bone marrow cancer, or acute promyelocytic Leukemia.

While vitamin A is regarded by some experts as a viable treatment, this is the first time that its use has been monitored for such an extended period of time.

Since the 18th century, arsenic compounds have been used as medicines to treat certain ailments. The US Food and Drug Administration approved it for the treatment of people with blood and bone marrow cancer in 2000.

(Reporting by Tan Ee Lyn; Editing by Alex Richardson)