Uterine and endometrial cancer both cause heavy vaginal bleeding. Sudden, heavy vaginal bleeding that soaks at least one pad every hour for 24 hours needs to be reported to a physician immediately. Bleeding between periods: Heavy spotting or an additional cycle in a month that occurs for more than two cycles should be evaluated by a doctor.
https://www.verywellhealth.com/cancer-symptoms-abnormal-vaginal-bleeding-513761

