Spindle cell sarcomas are part of a rare, heterogeneous family of connective tissue tumors. These tumors are primarily treated with surgery and have a high risk of recurrence and distant metastasis with elevated mortality rates. 1 Other than the evidence for first-line therapy with doxorubicin in advanced soft tissue sarcoma, little evidence exists to point to an optimal second-line therapy. This is due to the diversity of soft tissue sarcomas, which encompass approximately 70 different histologic subtypes that can each respond differently to treatment. 2 As such, newer strategies, including immunotherapy and targeted molecular drugs, are being developed.
Quiescent in most adult tissues, the Hedgehog signaling pathway, when inappropriately activated, has been implicated in the development of multiple types of cancers, including basal cell, breast, prostate, hepatocellular, pancreatic, and brain cancer. 3 The Hedgehog signaling pathway is an important regulator of cell growth and differentiation in early development, but when inappropriately activated can lead to cell proliferation and increased angiogenic factors, decreased apoptosis, and breakdown of tight junctions promoting cancer growth and metastasis. 4 Recent data reveal that the Hedgehog pathway plays a specific role in activation of satellite cells, proliferation of myoblasts, and differentiation of skeletal muscle. 5 Activation of this embryonic pathway has been implicated in embryonal rhabdoymyosarcoma, osteosarcoma, and chondrosarcoma. 5-7
This pathway has recently been recognized as a therapeutic target, with the development of vismodegib, a targeted Hedgehog pathway inhibitor. This novel agent is in active use for treatment of advanced basal cell carcinoma and is currently undergoing trials for various other malignancies. Recently, a phase 2a basket study, called MyPathway, evaluated the use of targeted therapies in 35 different advanced refractory solid tumors harboring specific molecular alterations. Out of 21 patients with mutations in the Hedgehog pathway, 3 had a partial response to vismodegib—one had an unknown primary tumor, another a squamous skin cancer, and the third a salivary gland cancer. 8 Vismodegib (GDC-0449) was also evaluated in a phase 2 multicenter clinical trial in patients with progressive advanced chondrosarcoma.7 Although the study did not meet its primary endpoint, the proportion of patients with non-progressive disease was 25.6% at 6 months. Investigators observed that the benefit occurred in the subset of patients with overexpression of the Hedgehog ligand. Genomic studies for mutations in SMO and PTCH genes were available for only 28 and 26 patients, respectively, of the 45 patients enrolled on the trial. While there were no mutations identified, expression data revealed that overexpression of the Hedgehog ligand was present in 65% of cases tested (13 out of 20 patients). In patients with stable disease at 6 months, all had overexpression of the Hedgehog ligand. 7 These studies point to the potential use of vismodegib in both bone and soft tissue sarcomas, and more specifically, to the importance of genomic testing in these cases.
Case Presentation and Summary
This report describes the novel use of vismodegib, an oral Hedgehog signaling pathway inhibitor, in the treatment of a patient with metastatic soft tissue sarcoma.
An 18-year-old female with no particular previous illnesses was initially diagnosed with superficial soft tissue sarcoma overlying the right hip in 2013. Due to the complexity of pathology, a second opinion was requested and revealed atypical cellular spindle and epithelioid cells, morphologically and immunohistochemically suggestive of spindle cell sarcoma, not otherwise specified. She underwent negative-margin resection in January 2014. Her course was complicated by two recurrences in the right inguinal lymph nodes in July 2014 and July 2015. She was treated with lymph node dissection in 2014, followed by numerous right lymph node dissections and adjuvant radiation in 2015.