Phase II trial of the histone deacetylase inhibitor, vorinostat, to restore hormone sensitivity to the antiestrogen tamoxifen in patients with advanced breast cancer who progressed on prior hormone therapy

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Background: Modulation of estrogen receptor signaling is one of the most successful modalities in the treatment of estrogen receptor (ER) positive breast cancers. However, hormone therapy resistance remains a challenging problem. Histone deacetylases (HDAC) have emerged as a recent strategy to interfere with hormone receptor signaling by modulating the estrogen and progesterone receptor. Here we report the findings from a phase II trial evaluating the HDAC inhibitor, vorinostat and the anti-estrogen, tamoxifen, placed in context with correlative studies. Methods: Patients with ER-positive metastatic breast cancer who progressed on prior hormonal therapy and up to three chemotherapy regimens were treated with 400 mg vorinostat daily for three of four weeks and 20 mg tamoxifen daily, continuously. Histone acetylation was evaluated in peripheral blood mononuclear cells. Results: To date, 29 patients [median age 53 years (34–71)] have been treated with the combination. Pulmonary emboli were observed in 2/29 (7%) patients. Other grade 3/4 toxicities included fatigue (5/29, 17%), anorexia (2/29, 7%), diarrhea (1/29, 3%), nausea/vomiting (3/29, 10%), hypokalemia (1/29, 3%), liver enzyme elevation (1/29, 3%), lymphopenia (5/29, 17%) and leukopenia (4/29, 13%). Predominant grade 2 toxicities included fatigue, nausea/vomiting/diarrhea, hyperglycemia, anorexia, and myelosuppression. Six (21%) patients had an objective response, and 3/29 (10%) additional patients had disease stabilization for >6 months; 13/29 (45%) patients had at least one prior chemotherapy regimen for metastatic disease, 28/29 (92%) patients had progressed after exposure to at least one and 16/29 (55%) patients after two aromatase inhibitors, and 18/29 (62%) patients had received prior adjuvant tamoxifen. H3 and H4 histone acetylation was seen at day 8 suggesting adequate vorinostat plasma levels. Histone acetylation and baseline HDAC expression will be presented. Conclusions: These findings suggest that the addition of an HDAC inhibitor to tamoxifen in patients who have progressed on prior hormonal therapy and/or adjuvant tamoxifen may restore hormone sensitivity.

No significant financial relationships to disclose.

Chemoprevention of breast cancer in the older patient

Age is the most important risk factor for the development of breast cancer. The risk of breast cancer continues to increase in American women until the age of 80 years. A family history of breast cancer helps identify those who possibly have the highest risk of developing breast cancer; however, most women who develop breast cancer do not have a first-degree relative with a history of breast cancer. Currently, the Gail model is a commonly used model to identify risk, and this model has now been validated in several populations of women undergoing screening for breast cancer. The first large-scale breast cancer prevention trial investigating the preventive effects of tamoxifen has demonstrated a decrease in the development of breast cancer by almost 50% in the women in the tamoxifen treatment arm as compared with those receiving placebo. The NSABP P-1 trial was the largest of the three tamoxifen breast cancer prevention trials and had the greatest power to detect a difference between the two treatment groups in breast cancer events. This trial also included the largest percentage of postmenopausal women. It is unclear why the Italian and Royal Marsden Hospital trials had negative results regarding the preventive effects of tamoxifen. These two trials were strikingly different from the NSABP P-1 trial, however, and they included a different population of women. The issues surrounding the use of HRT for treatment of hot flashes in the Italian and Royal Marsden Hospital trials adds to the controversy concerning the negative results of these trials. The new SERM, raloxifene, has shown promise in preliminary studies as a preventive agent for breast cancer. The STAR trial will open soon and will evaluate the efficacy of raloxifene in preventing breast cancer in a prospective fashion, comparing its efficacy with tamoxifen treatment. Other endpoints will evaluate side effects such as menopausal symptoms, endometrial cancer, thromboembolic events, and benefits regarding serum lipids and incidence of osteoporotic bone fractures. The development of SERMs results from an understanding of novel mechanisms of ER modulation and allows targeting for favorable effects in specific tissues. The challenge is to develop an ideal SERM that is effective in preventing breast cancer and does not increase the risk of endometrial cancer, while providing beneficial estrogenic effects on serum lipids and bone mineral density changes. Estrogen receptor-mediated intracellular processes are complex. There are at least two different types of estrogen receptors. The alpha receptors predominate in the breast and uterus, and the beta receptors predominate in the bone and blood vessels. Many proteins also interact with these receptors as co-activators or co-repressors. Transcription-activating factors modulate the effects of estrogen on its target genes. Future prevention strategies may use a combined targeted approach to inhibit ER-mediated cancer progression pathways. The retinoids are under investigation in prevention studies for a multitude of cancers, because they have been shown to inhibit cellular proliferation and to induce cellular differentiation. The retinoid 4HPR was selected for use in breast cancer prevention studies because of its low toxicity profile and prevention efficacy in preclinical studies. It is now being used in combination with tamoxifin in a phase II breast cancer prevention trial. Multiple surrogate endpoint biomarkers are being measured before and after treatment, including measurement of serum IGF-I levels. Future directions in breast cancer prevention include the development of more potent hormonal therapies that completely inhibit ER-mediated cancer progression and, ultimately, multitargeted therapies involving agents that work synergistically.

New Hormonal Therapies for Breast Cancer

BACKGROUND: There has been an explosion in the development of hormonal therapies for the treatment of breast cancer. Several new agents have been approved for the treatment of breast cancer in the metastatic setting, and trials are ongoing in the adjuvant and prevention setting to improve hormonal therapy for the prevention and treatment of breast cancer. METHODS: The literature on new hormonal therapies for the treatment of breast cancer is reviewed, with an emphasis on newer agents. RESULTS: Two antiestrogens are now approved in the United States for the treatment of metastatic breast cancer. Other antiestrogens have activity in metastatic breast cancer as well as in osteoporosis. Newer pure antiestrogens may overcome resistance to tamoxifen. Several aromatase inhibitors are available for the treatment of metastatic breast cancer. CONCLUSIONS: Many hormonal agents are now available for both adjuvant and advanced disease settings. Developments will depend on clarifying mechanisms of resistance to antiestrogens and identifying new classes of agents that lack cross-resistance to standard therapy.

Severe Lhermitte-Duclos disease with unique germline mutation of PTEN

Germline mutations in the PTEN gene have recently been identified in some individuals with Cowden disease (CD), Lhermitte-Duclos disease (LDD), and Bannayan-Zonana syndrome. We report on a patient with CD and LDD in whom a unique de novo germline missense mutation is present in the PTEN gene. Direct sequence analysis detected a transitional change (T-->C) at nucleotide 335, resulting in substitution of the amino acid proline for leucine. The mutation is in exon 5, which has been proposed as a "hot-spot" for germline mutations. Comparison of this patient's clinical course with the previously reported cases of CD and LDD shows more extensive and more severe clinical findings than reported previously. Findings in this patient contribute to the current understanding of germline PTEN mutations and clinical outcome.