AACR 2019—Virotherapy + radiotherapy shows activity in esophageal cancer


  • Univadis
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Takeaway

  • Combination virotherapy-radiotherapy with telomelysin (OBP-301) may offer an alternative to invasive therapies for medically fragile patients with esophageal cancers.

Why this matters

  • Standard therapy for esophageal cancer is invasive and not suitable for all patients, while combination virotherapy-radiotherapy is better tolerated.

Study design

  • Open-label, phase 1 dose-escalation trial of 13 patients (median age, 80 years) with histologically confirmed esophageal cancer deemed unfit for standard surgery or chemotherapy.
  • Patients were endoscopically administered 3 intratumoral injections of OBP-301, a genetically modified virus that radiosensitizes and selectively leads to cancer cell death, at doses ranging between 10 billion and 1 trillion viral particles.
  • Patients received concurrent radiation therapy totaling 60 Gy.
  • Funding: Ministry of Education, Science, and Culture in Japan, Japan Agency for Medical Research and Development.

Key results

  • Objective response rate was 85% (8 complete responses [CRs], 3 partial responses).
    • 83% and 60% of patients with stage I and stage II/III disease, respectively, achieved CR (endoscopically and pathologically). 
  • Posttreatment biopsies were malignancy-free in all patients.
  • There were no dose-limiting toxicities. 
    • Common toxicities were fever, esophagitis, pneumonitis, anorexia, constipation, and gastroesophageal reflux. 
    • All patients developed transient, self-limited lymphopenia. 

Limitations

  • Small sample size, no comparator group.

Expert comment

  • "A major concern with patients with esophageal cancer is not only treating the main tumor—it's treating micrometastatic disease," said Dr. Geoffrey Ku, head of the Esophagogastric Section of the Gastrointestinal Oncology Service at Memorial Sloan Kettering Cancer Center in New York, NY. "[OBP-301] may be kind of a 2-for-1 strategy in the sense that we're better able to get rid of the main tumor, but in the process of stimulating the immune system, we may also ultimately reduce the risk of patients developing metastatic disease," extending its benefits to a much larger group of patients beyond those too medically fragile to undergo surgery, he said.

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