Patients with early-stage breast cancer reciveiving clodronate are significantly less likely to develop spinal osteoporosis, findings from a prospective study suggest.

Even seven years after completing a three-year course of adjuvant therapy with the bisphosphonate clodronate, patients with early-stage breast cancer were significantly less likely to develop spinal osteoporosis than were patients who did not receive clodronate. This finding, from the longest prospective follow-up study of clodronate (also known as clodronic acid), was published in the September 10 issue of the Journal of Clinical Oncology.

It's "delightful news," Dr. Tiina Saarto of Finland's Helsinki University Hospital told Reuters Health, "that the effect of 3-year clodronate treatment is still seen seven years after termination of the therapy."

The study also found, consistent with other research, that baseline bone mineral density (BMD) is a major predictor of eventual osteoporosis.

The original study involved 268 newly diagnosed pre- and post-menopausal node-positive breast cancer patients. All underwent surgery and radiotherapy, as well as either chemotherapy or antiestrogen therapy. Patients were then randomly assigned to receive either 1,600 mg of oral clodronate daily for three years or no therapy.

BMD of the hip and the lumbar spine was measured before treatment and at one, two, three, five and ten years after therapy. At the ten-year point, 96 metastasis-free patients were still alive and eligible for follow-up. Seven patients with osteoporosis at the outset of the study were excluded from part of the analysis.

A previously reported follow-up at the three-year point (end of clodronate therapy) had found that the clodronate group had a significant reduction in bone loss, at both the hip and the lumbar spine. The present study found that between the three- and ten-year points, the rate of bone loss did not differ between the two groups.

Over the ten years of follow-up, 24 of 89 patients were diagnosed with osteoporosis at the hip and/or lumbar spine. Although the three years of clodronate therapy significantly reduced the incidence of osteoporosis versus the control group (P = 0.035), this reduction was seen only at the spine, not the hip (femoral neck and total femoral area). Overall, the ten-year spinal osteoporosis-free survival rate was 92.7 per cent in the clodronate group and 77.0 per cent among the controls.

In addition, the baseline BMD value was a strong predictor of osteoporosis. Of the 24 patients who developed osteoporosis at any site, 18 had osteopenia of the lumbar spine at baseline.

The most significant messages for primary-care physicians, Dr. Saarto said, are that breast cancer patients at risk for osteoporosis can be identified through BMD and that even short-term clodronate treatment provides lasting benefit.

J Clin Oncol 2008;26:4289-4295

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