How is your favourite research area doing?

Just out of curiosity I wanted to check out some of the publication trends on some of my favourite research topics. I used an online tool that outputs data the number of query publications for each year (available here). Below I plotted the results of a few. The queries with multiple words were put in quotations. Importantly the results for cancer in the plot were divided by 100 as to fit on the scale of the graph. So not only is cancer a much larger topic, with about 14 000 / 100 000 papers on pubmed, but it is also growing at over 100 / 100 000 papers every year. This is much faster than the other topics presented. Data up to to and including 2013 is included because the tool itself suggests that more recent data may not be very accurate.

I was fairly surprised to see the growth in papers on cancer stem cells especially when compared to oncolytic viruses. There are obviously lots of problems with evaluating a research area with this data. First is that the growth of a smaller topic may not be apparent when using data that is / 100 000 papers. Second is the issue of the query. It may not encompass the field well and a more popular term may be gradually replacing an older query. Third is that while there may be fewer papers, the papers that are published may be of higher impact factor. It is possible for example that oncolytic viruses are moving more into the clinic and that kind of research takes longer and the rate of publication may be reduced but the importance of the research may be greater than ever. A tool to evaluate the trends in impact factor of a query would be very interesting also.