It does NOT decrease cervical cancer. It DOES decrease endometrial and ovarian cancer though for the latter not as much as ring/patch/pill. Endometrial cancer by stopping the monthly ebb and flow of the endometrial lining. Less growth/shedding, less risk of cancer. Ovarian cancer b/c it does block ovulation but not as 100% as the ring/patch/pill. again, less frequent damage to the ovary (ovulation) and less risk of CA.