Scientists say poison could treat leukaemia.
Arsenic trioxide is already used on patients who suffer a relapse after initial treatment for acute promyeloctytic leukaemia (APL).
Scientists in Iran have said it should be considered as a firstline treatment for APL patients. They believe it could also target other cancers such as multiple myeloma.
Researchers at Tehran University of Medical Sciences ran trials on patients newly diagnosed with APL who had received no previous therapy.
After two courses of arsenic trioxide, over 90 per cent of the 63 patients were in complete remission.
The study, revealed at the European Organisation for Research and Treatment of Cancer symposium in Geneva, also showed that of the 11 patients who relapsed, eight went back into remission after a third cycle of treatment.
Six patients taking part in the trial have died.
The researchers said that 88.5 per cent of patients were still alive with a mean survival time to date of nearly 34 months.
APL, a cancer of the white blood cells, accounts for about ten per cent of acute myeloid leukaemias, affecting around 20,000 people around the world each year.
Arsenic trioxide works by causing changes in cancer cells which induce apoptosis - programmed cell death, and appears to correct the gene which makes flawed protein causing APL.
Lead researcher Dr Ardeshir Ghavamzadeh said: 'There have been a few studies done using arsenic trioxide on a limited number of newly diagnosed patients, but we are the first group to suggest that it is acceptable as a first-line treatment.
'The results are comparable to ATRA with chemotherapy and in our study it has actually proved to be better than ATRA with chemotherapy.
'What this means is that we now have the possibility of offering APL patients a new first-line treatment that avoids conventional chemotherapy.'
Pine cones grown in millions of gardens may hold the key to beating super-bug MRSA.
Scientists discovered the cones from common conifers contain antibacterial agents that help destroy the bug.
Researchers at the School of Pharmacy, University of London, studied cones from the Chamaecyparis lawsoniana, known as Lawson's Cypress. They discovered its immature pine cones contain antibacterial agents that were effective when tested against Staphylococcus aureus, or MRSA.