Help please! Is coitus good or bad for people who are suffering from cancer?

Good. For many (most?) adults, intercourse with someone they love is the most satisfying and meaningful of all activities. It is unlikely to affect the course of the disease itself, but it is an expression of love and is physically and emotionally satisfying. Even if there is no likelihood of conception, this act affirms the continuity of life and its new creation for someone perhaps facing death.