Endoscopic ultrasound (EUS) is a procedure typically performed by gastroenterologists, which has several different diagnostic and therapeutic modalities both within and outside gastroenterology.
Basically, EUS combines an esophagogastroduodenoscopy with an ultrasound probe on the end of the endoscope that allows for better visualization of the different layers of the gastrointestinal tract. It can be used to drain pseudocysts and abscesses without invasive surgical interventions. In addition, EUS can play a major role in both the diagnosis and treatment of cancer, and also has the potential to provide an innovative way of delivering localized chemotherapy.
EUS has been used to stage numerous cancers including pancreatic, esophageal, gastric, and rectal cancers. This is typically done with a fine needle aspiration (FNA) of the questionable lesion identified on imaging. EUS with FNA can be more effective in staging cancers compared with other imaging tests such as computed tomography and positron emission tomography scans. Early staging of cancer provided by EUS plays a significant role in the patient’s prognosis and treatment plan to follow.
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Just as EUS can use FNA to obtain a sample to help stage a cancer, it can also be used as a way to deliver more localized chemotherapy with fine needle injection (FNI). Perhaps its most significant role is in esophageal and pancreatic cancers, where it has been used for brachytherapy. Radioactive seeds are placed within the cancerous tissue; then the patient is exposed to radiation, causing localized lysis of the cancer.1
Prototypical chemotherapy agents, such as paclitaxel, have been reformulated and are currently being studied as an alternative to systemic chemotherapy. This formulation of paclitaxel is combined with a polymer that effectively creates a controlled drug release system.2 EUS with FNI can then be used to inject this version of paclitaxel into pancreatic tumors. The data is still being collected in clinical studies; however, this potentially represents a unique way to deliver chemotherapy.
Another interesting role for EUS in pancreatic cancer is the administration of anti-cancer biologic compounds. Once such biologic compound is called TNFerade™, which uses an adenoviral vector containing the tumor necrosis factor (TNF)-alpha gene that can be induced with chemoradiation.3 Upon induction, the TNF-alpha is up-regulated, causing tumor suppression and, eventually tumor lysis. Although the phase 3 trial of this compound was stopped early because the mortality benefit was not predicted to be statistically significant, it was still valuable in expanding the role for EUS in future cancer treatments.
As with any procedure, there are also associated risks. In the studies that have been conducted so far, the most common adverse events include nausea, vomiting, elevated liver function tests, abdominal pain, fevers, infection, and duodenal perforation. Since the use of EUS with FNI in administering some forms of chemotherapy is still a relatively new procedure, additional safety data needs to be collected.
EUS has been proven to play a substantial role in oncology, both diagnostically and therapeutically. The clinical data supporting it use continues to grow and new studies are needed in the future to further investigate its role in the local administration of chemotherapy.
References
1. Sun S, Xu H, Xin J, et al. Endoscopic ultrasound-guided interstitial brachytherapy of unresectable pancreatic cancer: results of a pilot trial. Endoscopy. 2006 Apr;38(4):399-403.
2. Vukelja SJ, Anthony SP, Arseneau JC, et al. Phase 1 study of escalating-dose OncoGel (ReGel/paclitaxel) depot injection, a controlled-release formulation of paclitaxel, for local management of superficial solid tumor lesions. Anticancer Drugs. 2007 Mar;18(3):283-9.
3. Senzer N, Mani S, Rosemurgy A, et al. TNFerade biologic, an adenovector with a radiation-inducible promoter, carrying the human tumor necrosis factor alpha gene: a phase I study in patients with solid tumors. J Clin Oncol. 2004 Feb 15;22(4):592-601. Epub 2004 Jan 15.
