Simplify the following text for a Grade 6 native English-speaking person.
Original: Currently , lung cancer is the leading causing of cancer death in women , killing more women than breast cancer , ovarian cancer and uterine cancers together . The large majority of people who get lung cancer have smoked for many years .
Simplified: Secondary cancers are classified by the site of origin ; e.g. , breast cancer that has spread to the lung is called breast cancer .