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Combination of Two Existing Drugs Offers Potential Alternative for Prostate Cancer: Presented at AACR-NCI-EORTC

By Maggie Schwarz

PHILADELPHIA, PA -- November 22, 2005 -- A combination of two drugs already in use to treat certain cancers offers a potential strategy to treat prostate cancer without subjecting men to treatments that squelch the production of testosterone.

The two drugs are granulocyte macrophage colony-stimulating factor (GM-CSF) and thalidomide.

Lead investigator Robert J. Amato, DO, Director of the Genitourinary Oncology Center, Methodist Hospital Research Institute, Houston, Texas, United States, presented the phase 2 findings here on November 16^th at the International Conference on Molecular Targets and Cancer Therapeutics.

The conference is organized jointly by the American Association for Cancer Research, the National Cancer Institute, and the European Organisation for Research and Treatment of Cancer (AACR-NCI-EORTC).

The protein GM-CSF stimulates immune system blood cell proliferation. It has been studied for its effects on colon,,ovarian and prostate cancer, and in myeloma, as well as other non-cancerous conditions such as Crohn's disease.

Thalidomide was prescribed in the 1950s and 1960s as treatment for morning sickness, but was banned from use when it became clear that it caused severe birth defects. Much of its deleterious effects on development in early body formation in babies were related to its function in thwarting angiogenesis. In addition to inhibiting angiogenesis, thalidomide contributes to enhanced immune response.

In their phase 2 trial, Dr. Amato and colleagues evaluated the combination of GM-CSF and thalidomide in prostate cancer patients; seven had undergone radical prostatectomy, six had radiation therapy and five had both. None had received previous hormone ablation therapy.

Treatment consisted of three weekly doses of GM-CSF and thalidomide once daily at bedtime. Doses were scaled to determine maximum tolerable levels of thalidomide. The researchers monitored prostate-specific antigen (PSA) levels at 6-week intervals.

"All of the men in the study had a 26% or greater reduction of PSA blood levels," Dr. Amato observed. "The median response was 59%."

Toxic events were all grade 1 or 2 in severity and manifested predominantly as transient skin rash, fatigue, peripheral neuropathy and constipation. However, one patient developed deep vein thrombosis and pulmonary embolism.

"GSM-CSF plus thalidomide can be used successfully with encouraging anti-tumor activity," Dr. Amato concluded. "The combination of GM-CSF plus thalidomide may constitute a significant improvement over current therapies."

Long-term androgen suppression therapy (more than 1 year) can lead to significant adverse effects, including bone density loss, anemia, breast enlargement, hot flashes, impaired memory and impotence in some patients, especially among elderly men.

"Existing hormone ablation therapy is effective and palliative," Dr. Amato asserted. "Many patients, however, hesitate to begin hormonal therapy due to the adverse effects."


[Presentation title: A Phase II Trial of Granulocyte-Macrophage Colony Stimulating Factor (GM-CSF) Plus Thalidomide in Patients with Hormone Naïve Prostate Cancer (HNPC): Abstract A49]

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