Yes, our species can be viewed as a cancer. The analogy fits. Kurt Vonnegut Jr referred to us as "cancer with a conscience."
Also, somewhere in the original book which the films Invasion of the Body Snatchers were based, there is a point where someone reflects that it does not really even matter if the pod people are spores of somekind from a distant galaxy, that the human species at this time may as well be the pod people themselves, for our general large-scale behavior is the same as the Body Snatchers.
I also once greatly romanticized life as a hunter-gatherer, but upon deeper reflection, and especially after reading Ligotti's CATHR, I lean more in the direction of believing that there has never been a good time to be alive.