Brast vs prostate cancer visualisation

Hi everyone,

I am learning how to graph data in R. I have taken two chunks of data from Eurostat:

- deaths reported by country in Erope from prostate cancer (males) between 1999 and 2010

- deaths reported by country in Europe from breast cancer (females) between 1999 and 2010

I put the two dataframes together, summed the deaths by year and the head() of the resulting matrix (count_year) was as follows:

Females Males
1999 181919 134708
2000 177844 132290
2001 205375 151810
2002 206757 153423
2003 206479 155612
2004 183488 141782

I made a graph using the above matrix and the following code:

matplot(rownames(count_year), count_year, type='l', xlab='Years', ylab='number of deaths', col=1:3)
> legend('bottomright', inset= 0, legend=colnames(count_year),
+ pch=1, horiz=TRUE, col=1:3)

And this is the graph, with its legend:

Now the question I have is, what do you think can be theorized about the two lines' shapes?
They look very similar which might mean that there's a variable I am not seeing which determines the ups and downs of these reported deaths. While it seems obvious that there are significantly more deaths from female breast cancer than prostate cancer, the fact that the two lines in the graph follow a similar pattern makes me very intrigued.
How would you approach this problem further, if you would at all?