lighthouse19something--------I apologize if you already know this stuff. I'm sharing for the sake of those who don't.
Don't remember the article, but cervical cancer has several risk factors, multiple partners being one of them. (Or, her partner having had more than one partner---you know the deal: Each partner your partner has had is basically the same thing as a partner for you, in terms of risk of catching/ spreading disease.)
The other cancer they are probably talking about is prostate cancer. Regular ejaculation (at least once a week, maybe?) keeps the prostate in good working order. So you can kind of liken it to a daily need to blow our nose....