Breast Cancer Chemoprevention by SOM230, an IGF-I Action Inhibitor

Ductal carcinoma in situ (DCIS) is a direct precursor of invasive breast cancer and is also a marker of an increased chance of developing invasive cancer in the ipsilateral and contralateral breast. Surgery and radiotherapy are used as treatment for DCIS and subsequent treatment with antiestrogens has been effective in reducing the occurrence of invasive breast cancer in DCIS patients. Unfortunately, treatment with antiestrogens carries potential side effects and toxicities. The investigators have data to suggest that inhibition of IGF-I action in the breast will be more effective than antiestrogens, raising hopes it might be effective enough to stand alone as a treatment. Pasireotide is a somatostatin analog that prevents mammary development by inhibiting IGF-I action directly in the mammary gland and also indirectly, without causing menopausal symptoms and signs. As both estrogen (E2) and progesterone (P) require IGF-I in order to act, part of the inhibitory effect of pasireotide is on prevention of estrogen action. The investigators have data that indicate that IGF-I also has direct actions on the breast that are independent of steroid hormones. One example is that IGF-I has a direct stimulatory effect on mammary development in the absence of E2. Additionally, IGF-I has effects on ER-negative tumor cell lines that can be reversed by IGF-I inhibition. If pasireotide inhibited both E2 related and E2 unrelated effects of IGF-I it would likely be more effective than antiestrogens. Preliminary data in rats show that pasireotide, at minimum, can entirely substitute for tamoxifen. To determine whether pasireotide had activities in women at high risk for breast cancer, similar to those observed in rats, the investigators were awarded a DOD Synergistic Idea grant. Those data are expected to be reported soon.

The investigators plan to expand this work to determine in principle whether pasireotide has the potential to treat DCIS. The investigators plan on treating 24 women, with low grade (8), intermediate grade (8) and high grade (8) ER-positive DCIS tumors. The investigators will assess its effect on apoptosis, cell proliferation, angiogenesis, ER and PR and phosphorylation of IGF-IR and IRS-1 before and after 20 days of treatment with pasireotide in core biopsy vs. surgical excision specimens. These endpoints will be measured by specific immunohistochemistry. Simultaneously, the investigators will determine whether IGF-I inhibition will reduce angiogenesis in DCIS using dynamic contrast enhanced MRI (DCE-MRI) at 3.0 Tesla, in addition to mammography. This MRI technique is able to detect early changes of neo-angiogenesis associated with invasive breast cancers and DCIS. Pasireotide should theoretically inhibit angiogenesis in these women, as it does in mice. The DCE-MRI may also show changes in tumor volume, morphologic and kinetic features. Imaging will serve as an additional measure to monitor response to treatment. Results will be correlated with pathology and immunohistochemical endpoints.

In our previous work the investigators noted that there was an increase in blood glucose early after starting pasireotide, but the work of others has indicated that this side effect lasts only several weeks. The investigators found that suppressed levels of insulin (due to pasireotide effect on β cells) began to rise by day 10 of treatment. Therefore, extending the treatment period from 10 to 20 days with daily monitoring of patients will enable us to make certain that the early elevated glucose associated with pasireotide is only temporary. Another side effect is reduction in circulating levels of IGF-I. Theoretically, this could lead to body changes associated with growth hormone deficiency (GHD). Although, tamoxifen and raloxifene also lower serum IGF-I, and women taking it do not usually complain of symptoms of GHD, this is an issue that must be further investigated. However, if pasireotide is found to be effective in the treatment of DCIS, the benefit would likely outweigh the risk.