Study Coordinator(s): Katherine Crew, M.D.
Participants: Members, CCOP, Affiliates, Medical Oncologists, Surgeons, CTSU
Eligibility Criteria: Premenopausal women, elevated risk of breast cancer by either diagnosis of ADH, ALH, LCIS (lobular neoplasia) or resected DCIS or small invasive BrCa (pTmi or pT1a N0) ir not prior breast RT, Tamoxifen or systemic BrCa Tx within 28 days prior to registration or Diagnosis of resected Stage I 9T1b-c, N0-N1mi) - Stage II breast cancer for whihc the participant has been disease-free for at least 5 years and has completed all adjuvant tx or a known deleterious mutation in BRCA1, BRCA2, PTEN or TP53 by genetic testing or Modified Gail/CARE model risk at 5 yrs >/= 1.67% or lifetime risk >/= 20% by Claus, BRCAPro, Tyrer-Cuzick, IBIS models or Gail Model (in women >/= 35 years) or mammographic breast density >/= 50%; one non-irradiated breast available for imaging and biopsy; baseline bilateral digital mammogram with normal or benign findings AND mammographic density >/=10% performed within 10 days LMP; (Participants with abnormal breast imaging are eligible as long as the breast biopsy is benign and shows no evidence of cancer); baseline serum 25(OH)D </=32 ng/mL or </= 80 nmol/L w/in 28 days of registration; prior tamoxifen o.k. if discontinued >/= 28 days before registration; prior breast surgery or prior breast irradiation for resected DCIS or small invasive breast cancers (Tmi or T1 N0) o.k. if > 28 days prior to registration; Zubrod PS 0-1, age 18-50 years; serum creatinine and corrected calcium </= ULN; spot urine calcium/creatinine ratio </=0.37 withing 28 days prior to registration;no history of kidney stones; any anticoagulant therapy discontinued at least 7 days before biopsy; no calcium or vitamin D supplements while on protocol; multivitamin with </= 400 IU daily of Vitamin D o.k.