# Developing silastic-silicone for the local delivery of hormonal therapy to prevent and treat breast cancer

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN FRANCISCO · 2021 · $362,569

## Abstract

Project Summary/Abstract:
 Breast cancer remains a considerable health concern. With the recent increase in affordible multi-gene
germ line testing, an estimated 0.5-1 million women, many very young, will be in need of intense breast
cancer screening and prevention options. Options to prevent breast cancer in women with high risk currently
include bilateral mastectomies, or anti-estrogen therapy and premature menopause. For most women, these
are grim choices. Localized delivery of an anti-estrogen to breast tissue may be an attractive alternative for
cancer prevention and may further provide an alternative to systemic therapy for ductal carinoma in situ
(DCIS) and early stage breast cancer with minimal risk for metastasis.
 We, therefore, propose the use of a silastic-silicone device placed under breast tissue as a local delivery
strategy for anti-estrogen therapy. The slow release of an anti-estrogen from silastic-silicone directly into the
breast parenchyma with preferential breast tissue uptake will achieve a high local concentration while
minimizing systemic exposure.
 In preliminary in vitro and in vivo data, we show that approved anti-estrogens can be delivered through an
implantable silastic-silicone device that provide sustained high levels of drug that inhibit estrogen receptor
(ER) signaling and breast cancer cell proliferation. Silastic-silicone delivers fulvestrant selectively to mouse
mammary tissue for more than 1 year with anti-tumor effects similar to those acheived with systemic
fulvestrant exposure.
 In this application, we propose to test and refine this localized drug delivery strategy in an inducible
prevention model and large animal model. In three specific aims, we will (Aim 1) determine the efficacy of
silastic-silicone released fulvestrant to prevent tumor formation in an inducible rat breast cancer model and
establish estradiol-PET imaging as a co-diagnosic for tumor ER modulation, and (Aims 2 and 3) optimize the
design of the device, characterize drug diffusion and penetration properties in tissue utilizing a large animal
goat model. These experiments will lay the ground work for rapid clinical translation to initial safety and
efficacy studies in a breast cancer DCIS setting with a companion imaging biomarker.
 The greater awareness and genetic identification of individuals at risk for breast cancer comes with an
increased need for new approaches to breast cancer prevention. The development of a silastic-silicone based
device for sustained local drug delivery with an approved and effective anti-estrogen should allow rapid
transition into clinical testing. This strategy will provide an alternative option to delay or forgo mastectomies to
the rapidly increasing number of young women identified to have a more than 40% lifetime chance of
developing breast cancer. If successful this therapeutic approach should be transferable to other tumors and a
broader range of anti-cancer agents.

## Key facts

- **NIH application ID:** 10180911
- **Project number:** 5R01CA220131-05
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
- **Principal Investigator:** Pamela N. Munster
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $362,569
- **Award type:** 5
- **Project period:** 2017-07-01 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10180911

## Citation

> US National Institutes of Health, RePORTER application 10180911, Developing silastic-silicone for the local delivery of hormonal therapy to prevent and treat breast cancer (5R01CA220131-05). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10180911. Licensed CC0.

---

*[NIH grants dataset](/datasets/nih-grants) · CC0 1.0*