Scientists are using the equations Google employs to predict the Web pages users visit to track the spread of cancer cells throughout the body.
“Each of the sites where a spreading, or ‘metastatic,’ tumour could show up are analogous to Web pages,” said Paul Newton, a mathematician at the University of Southern California, who has been working with cancer specialists at the Scripps Research Institute.
Google ranks Web pages by the likelihood that an individual would end up visiting each one randomly. These predictions are based on the trends of millions of users across the Web using “steady state distribution”.
“It occurred to me that steady state distribution is equivalent to the metastatic tumour distribution that shows up in the autopsy datasets,” Newton explained.
The dataset he’s referring to contains information about autopsy patients from the 1920’s to the 1940’s, who died before chemotherapy was available.
By focusing on this group of patients, the researchers could track the natural progression of cancer, specifically lung cancer, without different treatments interfering with the data.
Out of fifty metastasis sites described in the autopsy reports, scientists found that twenty-seven contained cancer that appeared to have spread from the lungs.
Just like with an individual browsing the Web, cells that break off from the original lung tumour and entered the bloodstream have a certain probability of progressing to different locations.
Following Google’s example with search results, researchers were able to estimate the average time it takes the cancer to spread to different parts of the body. The lymph nodes were the quickest to be affected by metastasising lung cancer cells, followed by the adrenal gland and liver.