Hi,
Modern medicine approaches cancer using a multimodality approach.
Local control is established by surgery and radiation therapy, while chemotherapy is useful for systemic therapy.
You are right that some normal cells get damaged by chemotherapy. Recent advances include the use of monoclonal antibodies for targeting structures only found in cancer cells.
Such target therapy causes very little "collateral damage", and normal cells are hardly harmed.
In advanced cancer, chemotherapy is often the only feasible option left.
All the best, and God Bless!