According to a study carried out by Harvard researchers, more than a third of the cancer deaths are caused by nine risk factors, all of which can be controlled.

The Harvard team examined major cancer types, including lung, breast, stomach, liver, colorectal, pancreatic, cervical, uterine, oral, oropharynx, and esophageal, as well as leukemia.

They did not include prostate and kidney cancers, or melanoma and lymphomas, because they are not associated to the nine risk factors assessed.

Smoking, alcohol use, low fruit and vegetable intake, overweight and obesity, unsafe sex, urban air pollution, physical inactivity, contaminated injections in healthcare settings, and/or indoor smoke from household use of solid fuels were responsible for 2.43 million deaths of the total number of cancer deaths.

The researchers concluded that in the countries with low and middle incomes, smoking, alcohol use and low fruit and vegetable intake were one of the most important risk factors, while in the high income countries, the last factor was replaced by obesity.

BBC quoted lead researcher Dr Majid Ezzati as saying that smoking was by far the most important risk factor for cancer, alone responsible for 21% of cancer deaths worldwide.

In addition, he said public health campaigns targeting smoking in the UK had led to a drop in deaths from lung cancer in the past few decades.