Pancreatic cancer is one of the most challenging malignancies to treat, and recurrence is common, even after initial treatment with surgery and radiation. When the cancer does return, treatment options are often limited to chemotherapy, but researchers at Georgetown's Lombardi Comprehensive Cancer Center are utilizing the precision allowed by CyberKnife® to see if radiosurgery is a viable treatment option in select patients.
"When treating recurrent pancreatic tumors, there are a number of factors to evaluate before we can consider radiosurgery as an additional treatment option," explains Christopher Lominska, M.D., lead author of the study and a resident in radiation medicine at Georgetown's Lombardi Comprehensive Cancer Center. "First, treatment must be safe, which is demonstrated in this study. We also designed a treatment that can be delivered in a short period of time -- a critically important quality-of-life factor in this patient population." The results of the study were presented today at the 50th annual meeting of the American Society for Therapeutic and Radiology Oncology (ASTRO) in Boston.
For the study, Lominska and his colleagues evaluated the safety of radiosurgery using CyberKnife® by reviewing the records of patients treated for pancreatic cancer at Georgetown from June 2002 through July 2007. Twenty-eight patients were treated for locally recurrent disease, 20 of whom had had prior chemotherapy and conventional radiation, and eight of whom had had prior surgery as well as radiation and chemotherapy. Disease recurrence was visualized with CT or PET/CT imaging.
The median age of the patients was 63 years old. Follow-up was available on 24 of 28 patients (patients lost to follow-up were assumed deceased). Median survival from the date of radiosurgery treatment was 5.3 months (range 1-27 months). Seven (7) patients (25 percent) lived more than 8 months after treatment.
"We found an acceptable safety profile for those receiving radiosurgery," says Lominska. "These patients had received full doses of conventional radiation therapy prior to their radiation treatment, so this speaks to the very high level of precision of the CyberKnife® -- that we were able to give them more radiation safely. It's also worth noting that treatment was delivered in only a week allowing patients to resume systemic chemotherapy with minimal interruption."
Lominska says only two patients experienced serious GI toxicity (one peripancreatic abscess, one bowel obstruction) after being treated with three sessions of radiosurgery. (Five sessions of daily treatment are now commonly given with the belief that this is better tolerated.) Review of radiographic studies revealed local control in 6 patients, local control with distant progression in 6 patients, and local and distant progression in two patients with no follow-up imaging available on the remaining patients. As of March 2008, 26/28 patients have died. The two surviving patients remain locally controlled without evidence of distant disease on follow-up of three and 8 months.
Lominska says the preliminary survival trends look good, but are not conclusive until more studies are designed to evaluate if radiosurgery with CyberKnife can extend survival when compared with usual care.
In addition to Lominska, other study authors include Nadim Nasr M.D., Natalie Silver M.S., and Gregory Gagnon M.D., all of Georgetown. The authors report the following disclosures: Gagnon occasionally serves as a paid consultant and receives speaking fees from Accuray, the manufacturer of the CyberKnife. There was no external funding for this study.
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