Re: So manslaughter is OK
The important part is "were going to anyway".
If it was a situation where the cancer had already staged and spread *and would have been in that condition* when the screening session was missed then probably it would be impossible to prove that a detection at a late stage and treatment would have resulted in a cure... Therefore you really couldn't argue manslaughter, at best medical negligence.
However. If the cancer would have been detected before staging or very early I or II (for example in a very aggressive cancer like my partners (although that was also to do with her age)) and there is a reasonable chance that a cure could have been effected if it had been caught in time then manslaughter *could* be argued since, as I understand it, manslaughter means you either accidentally caused or *contributed to* by material actions or in this case inaction the death of the individual concerned - although whether it'd succeed is another matter.
The problem is that it would be what lawyers call a "technically interesting" case which to quote the great Sam Vimes (I believe) is lawyerese for "$600 a day plus overtime, and it'll take months".