Novel treatment options in advanced adenoid cystic carcinoma of the breast.

e13071 Background: Adenoid cystic carcinoma (ACC) accounts for less than 0.1% of all breast cancer cases. The disease typically remains localized and indolent, and frequently occurs with triple negative status. Methods: In patients with locally advanced or metastatic disease, chemotherapy for triple negative breast carcinoma is seldom effective. Thus new treatment paradigms are desired. Drug targeted analysis derived from next generation sequencing and identification of driver mutations may offer a bright future in treatment options in chemo-resistant malignancy. Results: A 53 year old woman presented with breast mass and mastectomy with stage pT3N0M0 triple negative ACC of the breast resulting in observation. She later relapsed with chest wall disease, resulting in resection and radiation therapy. Shortly thereafter, she relapsed with pulmonary metastatic disease. She was treated with carboplatin and doxorubicin which were discontinued due to disease progression. Liquid assay revealed an IDH2 mutation, prompting treatment with enasidenib with ongoing evidence of disease control at 4 months. Patient tolerated treatment well without grade 3 or 4 adverse reactions. A 48 year old woman presented with an increasing 9.5 cm unresectable breast mass without distant metastasis. Pathology showed triple negative ACC of the breast, resulting in chemotherapy with doxorubicin, cyclophosphamide, and paclitaxel with clinically progressive disease. She represented with necrotic and ulcerating changes of the breast. Foundational genomic testing showed an FGFR2 mutation. After four months of treatment with erdafitinib, she had resolution of pain and cessation of pain medication. Her therapy led to a grade 2 adverse event related to hyperphosphatemia. She underwent surgical resection with negative margins. Conclusions: These examples illustrate a potential treatment paradigm for a rare malignancy for which there is no standard of care. Here we present two desperate cases, one of which had a driver mutation of IDH2, and the other FGFR2 for which there are targeted therapies approved in other disease states. The use of these two agents resulted in clinical benefit. A patient with metastatic disease treated with enasidenib has ongoing disease control for over 4 months with minimal adverse reaction. A patient with advanced local disease requiring narcotics and gabapentin for pain control treated with erdafitinib had significant symptomatic control with successful cessation of pain medications and ability to undergo potentially curable mastectomy with negative margins despite progression on prior chemotherapy. In summary, ongoing research of ACC of the breast will be required. Alternative therapeutic options related to targeted treatment may offer promise to clinical outcomes in the future. For cases of locally advanced or metastatic disease, the use of targeted therapy may offer new therapeutic options.