I think that the usage of 'recurrence' and 'spread' is confusing as well. The only objection I have to the word spread is that it can imply, in common usage, that cancer cells were somehow missed during surgery or not deactivated during radiation or chemo. That is, in a sense, it can allow an inference that physicians didn't do a good job and missed something that then "spread." [I'm thinking particularly of melanomas and other skin cancers which were later found to be incompletely removed. It's a very scary thing and I know two people who died of a likely preventable cancer because a dermatologist removed too little tissue. ]

Even the word recurrence can be confusing because it suggests that a certain kind of cancer occurred a second time but in fact a recurrence can have a totally different genetic profile than the original. Or can share the same profile.

The imprecision of the language makes it tricky when reading medical research because one needs to know exactly what is meant by recurrence or spread. To me, it seems as if the better term would be 'subsequent occurrence' but the odds of changing the common terminology are slim I suspect.