Can cancer in the uterus cause irregular periods lasting over 7 days ?

Yes: The first signs of uterine cancer are often abnormal vaginal bleeding, particularly after going through menopause. This requires urgently being seen by a gynecologist.

Vaginal spotting.: Technically, cancer in the uterus, primarily endometrial cancer, most often arises during the 6th and 7th decades, long after menopause. Thus it is not a period, but blood from the dysplasdtic/cancerous endometrium, that is seen as discharge or bleeding. Leukorrhea or a thick, whitish vaginal discharge is also often seen. If you or anyone you know has this, see your doctor soon for work-up & rx.