The purpose of this study is to evaluate the effectiveness of once weekly risedronate in the prevention and treatment of bone loss in premenopausal and newly menopausal women with breast cancer who have received chemotherapy.

The hypothesis is that bisphosphonate therapy will prevent bone loss at clinically relevant sites, such as the hip and spine. The investigators also hypothesize that there will be a correlation between biochemical markers of bone turnover and changes in bone mineral density.

Breast cancer is a significant public health problem accounting for approximately 30% of new cancers diagnosed annually. Much advancement has been made in the treatment of these cancers which has significantly decreased the mortality rates. Treatment, including adjuvant chemotherapy and hormonal therapy, prolongs disease free survival and overall survival of patients with breast cancer. The cytotoxic drugs, however, can cause premature ovarian failure and subsequent menopause. This risk has been reported to range from 53% to 89%. Temporary or permanent chemotherapy induced ovarian failure is important because of potential bone loss associated with the estrogen loss. Initiating a potent antiresorptive agent, risedronate, should prevent or improve bone mass in these women.

Comparison: The investigators will compare bone mass/markers of study subjects receiving risedronate with study subjects receiving placebo. All subjects will be provided calcium and vitamin D supplementation as needed.

Inclusion Criteria:

• Pre- and newly postmenopausal (up to 8 years) women ages 18 and older
• Breast cancer treated with chemotherapeutic agents, with or without tamoxifen/aromatase inhibitors
• Negative pregnancy test

Exclusion Criteria:

• Stage 4 breast cancer
• Any illness or medications known to affect bone metabolism
• History of osteoporosis or history of vertebral or hip fractures
• Kidney stones in the past 5 years
• Active peptic ulcer disease