November 8, 2010 (San Diego, California) — Adjuvant radiation therapy is beneficial after surgery for pancreatic cancer, according to the results of a large population-based study. The results of the study, presented here at the American Society for Radiation Oncology 52nd Annual Meeting, show that radiation therapy after surgical resection is strongly associated with improvements in both cause-specific survival and overall survival.
For the entire cohort, the median overall survival was 17 months. Patients who underwent surgery alone had a median overall survival of 15 months; for those who received adjuvant radiation therapy, it was 20 months.
In the surgery-only cohort, 1-year survival was 55.8% and 2-year survival was 31.6%. In the radiation therapy cohort, 1-year survival was 72.2% and 2-year survival was 40.4%.
"We did find radiation therapy to be significant for overall survival," said lead author Krisha Opfermann, MD, from the Medical University of South Carolina in Charleston.
On multivariate analyses, for those who underwent surgery, improved overall survival was associated with "a higher number of lymph nodes resected, a lower absolute number of positive resected lymph nodes, a lack of regional extent of the disease, a lower lymph node ratio, and more recent diagnosis," she explained.
For those who received radiation therapy, "the year of diagnosis and the regional extent of the disease" no longer affected overall survival, Dr. Opfermann said.
Commenting on the paper, Salma K Jabbour, MD, from the Cancer Institute of New Jersey in New Brunswick, noted that "this was a very unique trial."
Among lymph-node-positive patients, radiation therapy improved survival in most groups of patients, she said.
Statistically Significant Relationships
The role of adjuvant radiation therapy after surgical resection in pancreatic cancer remains controversial, Dr. Opfermann said, even though a benefit has been seen. In several previous studies, radiation therapy has appeared to be beneficial in patients with extensive disease or involved regional lymph nodes.
In this study, the authors explored the association between what they termed the lymph node ratio (the ratio of involved nodes to nodes resected) and outcomes among pancreatic cancer patients who received adjuvant radiation therapy.
Using the Surveillance, Epidemiology and End Results (SEER) database, they identified 3586 patients who received a diagnosis of pancreatic cancer from 1998 to 2006. All patients had undergone surgical resection, had a pathologic examination performed of the regional lymph nodes, and had a survival time of at least 2 months. Among this group, 1698 patients had also received radiation therapy.
Among the shortcomings of the SEER database, however, said Dr. Opfermann, "is that there are no chemotherapy data available, and that surgical margins are not available."
The authors found that there were statistically significant univariant relationships for reduced cause-specific survival and overall survival for fewer resected lymph nodes; more positive lymph nodes; earlier year of diagnosis; increasing T stage, disease stage, and extent of disease; and lack of adjuvant radiation therapy.
For cause-specific survival, patients treated with surgery alone had a hazard ratio (HR) for the number of positive lymph nodes (per increase of 5) of 1.05 (P < .001); the HR for the lymph node ratio was 3.15 (P < .001).
Among patients treated with radiation therapy, the HR for the number of positive lymph nodes (per increase of 5) was 1.31 (P < .001), and the HR for the lymph node ratio was 2.61 (P < .001).
Findings were similar for overall survival. For patients who underwent surgery only, the HR for the number of positive lymph nodes (per increase of 5) was 1.46 (P < .001), and the HR for lymph node ratio was 2.96 (P < .001).
In analyzing overall survival among patients who received radiation therapy after surgery, the HR for the number of positive lymph nodes (per increase of 5) was 1.29 (P < .001) and for the lymph node ratio was 2.47 (P < .001). When the authors stratified the lymph node ratio into discrete cutpoints, there was a statistically significant HR for the cutpoints of 20% or below, 20% to 40%, and 40% or above in both groups with respect to cause-specific survival and overall survival.
The authors have disclosed no relevant financial relationships.
American Society for Radiation Oncology (ASTRO) 52nd Annual Meeting: Abstract 216 Presented November 3, 2010.
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