Complex sentence: Mitotic inhibitors are used in cancer treatment, because cancer cells are able to grow and eventually spread through the body (metastasize) through continuous mitotic division and so are more sensitive to inhibition of mitosis than normal cells.
Split into simpler sentences: Mitotic inhibitors are used in cancer treatment, because cancer cells are able to grow and eventually spread through the body (metastasize) through continuous mitotic division. Thus, cancer cells are more sensitive to inhibition of mitosis than normal cells.