- Negative pregnancy test (serum beta-human chorionic gonadotropin [HCG]) within 7 days of starting study treatment is required in women of childbearing potential; neuroendocrine tumor (NET) patients with positive beta-HCG are eligible if pregnancy can be excluded by lack of expected doubling of beta-HCG; the usual beta-HCG doubling time is every 2 days during the first 4 weeks of pregnancy and lengthens to every 3 ½ days by weeks 6 to 7; patients can also be eligible if pregnancy can be excluded by vaginal ultrasound in consultation with Obstetrics/Gynecology