PageRank and Lung Cancer
Google’s PageRank method allows one to analyze web networks based on links between certain webpages and apply the findings to search engine results. One can interpret this as an analysis of the how users spread themselves across the web, based on how they travel through links to other web pages. Somewhat recently, researchers analyzed autopsy data from 163 cancer cases in an attempt to mathematically describe how cancer spreads throughout the body. They discovered that cancer cell movement tends to occur in multiple directions, rather than to a single primary destination. Moreover, certain organs disperse cancer cells more than others, which might just harbor tumors. For instance, according to the findings kidneys often spread cancer cells more aggressively than livers do.
One can make a clear comparison between this network of cancer spreading organs and that of PageRank with the web. The researchers essentially applied PageRank to tumors for certain organs, rather than web pages. Graphs were established, in which nodes represented organs and edges represented the spread of cancer cells. Organs are assigned PageRank values based on how widely they are likely to spread cancerous cells, and the PageRank method is used to analyze how the network changes over time. More precisely, one regards the system of organs as a Markov Chain that undergoes state transitions after some period of time, representing the spread of cancerous cells over time. Such analysis allows one to establish a rather simple model to predict which organs are most likely to spread cancer (in this specific case, lung cancer) throughout the body, which could have a significant impact on those seeking to improve treatment methods. Of course, such a model cannot encapsulate every possible variable in these situations, but it offers a useful way to analyze and treat complex diseases.
The ideas used in PageRank extend beyond the scope of the web and search engines. Markov chain models and graphs have applications in the understanding of the nature of certain diseases. It is necessary to understand how cancer spreads throughout the body and which organs are most likely to be impacted if one seeks to successfully treat the disease. Thus, simple probabilistic tools such as the ones used in PageRank could prove vital to our attempts to understand and eventually cure cancer.
Source (s):
https://gigaom.com/2013/03/26/how-researchers-are-fighting-lung-cancer-using-pagerank/