British scientists have unlocked the genetic code of lung and skin cancers in a breakthrough that is expected to transform the way cancers are diagnosed and greatly improve the efficacy of their treatment in the near future.

Published in the journal Nature, the study was carried out by scientists at the Wellcome Trust Sanger Institute, which was part of the international Human Genome Project that first cracked the human genome in 2003.

Following this giant leap, scientists are predicting that by 2020, all cancer patients could have their tumours analysed to find the genetic defects that drive them, The Times newspaper said on Thursday. This information would be used to select the treatments most likely to work.

The genetic maps of lung cancer show that most mutations can be traced to the chemicals in tobacco smoke. Similarly, mutations in malignant melanoma - a deadly skin cancer - are caused by ultraviolet light, the study reveals. Thus, both cancers are largely preventable.

The findings identified specific DNA mutations in genes that were triggered by environmental factors such as tobacco smoke, harmful chemicals or ultraviolet radiation, causing the cells to grow out of control and cause deadly tumours.

India is among the dozen countries working to identify all the genes that mutate to cause cancers, with its national Cancer Genome Anatomy Project focusing on cancers of the oral cavity (mouth), which is among the top three cancers in the country.

Stomach cancer is being studied in China, breast cancer in the UK, cancers of the brain, ovary and pancreas in the US, and liver cancer in Japan.