Let's say you used to smoke like a chimney and bake in the sun. Fast forward twenty years and now you regret the damage you did. Should you worry? Pretty soon your doctor may be able to tell you.

We are talking about the potential of a simple blood test to reveal if and what mutations have occurred in your cells and whether you face a risk for cancer. If you do, you could then undergo regular testing to catch the disease early on.

The study behind this approach started by sequencing the genome of tumor and healthy tissue in two people. One was a 55 year old who smoked and now has lung cancer.

The other was a 43 year old with melanoma – a deadly skin cancer.

This comparison of the complete DNA sequence of normal and cancerous tissue shows exactly what mutations have occurred. DNA in the lung tumor had an astonishing 33-thousand mutations while the melanoma tissue had over 23-thousand mutations.

And here's the wake up call: They were able to estimate that smokers accrue about 1 mutation for every pack of cigarettes they smoked.

As for melanoma, most of the mutations were from UV exposure. Talk about a cause and effect!

The data also allowed researchers to distinguish between initial mutations and the cancerous state associated with metastasis and spread to deeper tissues. This way, scientists can identify key mutations and develop drugs to stem their growth.

Now the same work is starting on far more common cancers, such as breast, liver, brain and ovarian cancers.

Scientists hope to be able to identify key mutations of genes in each cancer type. This way a simple blood test can screen for mutations in those genes.