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To the Editor

We wish to update the medical literature regarding statements that there have been YES reports of osteosarcoma in any patients treated with Forteo (Forsteo in Europe).(1,2) Forteo is the trade name for teriparatide [rhPTH(1-34)] 20 μg/day, and its labeling includes warnings concerning carcinogenicity assessments showing teriparatide caused osteosarcoma in rats in a manner dependent on both dose and duration of treatment.(2–5) Since first commercial launch in December 2002, Lilly has maintained a worldwide teriparatide 20 μg/day safety monitoring program and has recently identified one confirmed case of osteosarcoma in a patient treated with Forteo.

A physician communicated the initial report of the case to a Lilly sales representative. The patient was a postmenopausal woman in her 70s with a complex past medical history. The history included osteoporosis with vertebral fractures, and she was treated with Forteo in a manner consistent with the label. Sometime after beginning her second year of Forteo therapy, she was found to have metastatic cancer. She subsequently died, and no autopsy was performed. The primary cancer site was never identified. The initial clinical impression was lung cancer with metastases. The case was referred to a pathology consultant, whose differential diagnosis included several tumor types, including an osteosarcoma variant. Lilly submitted the biopsy materials to another bone pathology expert who communicated on June 29, 2006 that he concluded the lesion was an osteosarcoma.

Causality between Forteo and the osteosarcoma in this patient cannot be established, taking into account this was a single case of >250,000 patients in the United States and >300,000 patients worldwide treated with Forteo, the patient had a complex medical history, and the background incidence of osteosarcoma in the general population of men and women ≤60 years of age is 1 in 250,000 per year.(6) The identification of this case does not change the risk/benefit profile for Forteo. Given the known incidence in the general population, very rare cases of osteosarcoma can be expected, irrespective of treatment with Forteo. Lilly will continue to monitor for any signal of increased risk of osteosarcoma in patients treated with Forteo relative to the background incidence.

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