Mention the words “pancreatic cancer” to someone, and the response is likely to be a grim shake of the head.
For a cancer that is so enigmatic, its reputation is widely known: most of those diagnosed with the disease succumb to it. But City of Hope researchers are now spreading the word that certain surgical steps appear to give some patients a survival advantage.
According to a study by City of Hope surgical oncology fellow Minia Hellan, M.D., and her colleagues, the number of lymph nodes removed in surgery for early stage pancreatic cancer is associated with patient survival. Hellan presented the research at the American Society of Clinical Oncology (ASCO) Gastrointestinal Cancers Symposium in January and garnered a Merit Award from ASCO in recognition for the work.
Specifically, Hellan said, removing between 10 and 20 lymph nodes appears to provide the most benefit.
Surgeons today have no national guidelines for the number of lymph nodes they should remove during these surgeries, she explained. “In the top centers, surgeons usually remove 13 to 23 nodes,” Hellan said, “while in some settings, in community hospitals, they may remove only seven or fewer.”
Senior author Joseph Kim, M.D., assistant professor of surgery, conceived the idea of the study because the extent of pancreatic cancer’s spread to lymph nodes is a critically important question to answer.
“Cancer spread affects prognosis and may determine therapy,” Kim said. “It should be evident to anyone that the removal of one lymph node — even when cancer is not detected — is inadequate to accurately determine whether lymph node metastasis has occurred. With this in mind, it was my goal to determine whether the number of lymph nodes that were removed and analyzed for patients with pancreatic cancer were important for determining survival.”
Hellan began by examined the Surveillance Epidemiology and End Results database, a compilation of cancer cases from registries nationwide.
She studied 1,915 cases of pancreatic cancer in which patients had either stage 1 or 2 disease, with no evidence of cancer in lymph nodes.
Of the 31,000 cases of pancreatic cancer diagnosed each year in the United States, about 15 to 20 percent are found at an early enough stage so that surgeons can operate and remove the tumors, she said. More of these cancers now are being discovered through imaging scans, and more are found while the cancer is still confined to the pancreas. Since the surgical procedures have become much safer, as well, more patients are now qualifying for such surgeries, she noted.
In these operations, surgeons remove tumor tissue, as well as some surrounding healthy tissue and lymph nodes so that pathologists may test the tissue and nodes for evidence of cancer spread.
According to the study, patients who had 10 to 20 lymph nodes removed had better survival rates than those who had fewer than 10 removed. Among those with stage 1 disease who had 10 to 20 nodes removed, the five-year survival rate was 31 percent; but among those with stage 1 disease who had fewer than 10 nodes removed, the five-year survival rate was 18 percent. Yet nearly three-quarters of the centers she studied removed under 10 lymph nodes; and the average number of nodes removed was seven.
Researchers do not know why the number of lymph nodes removed is tied to outcome. Removing lymph nodes might remove microscopic metastases or it might identify more cancers that have spread, pushing them into the category of later-stage cancers.
“Our study results show that the lymph node number is important and may be related to surgical and/or pathologic expertise,” Kim said. “These results reinforce the concept that patients with pancreatic cancer should seek treatment in centers that specialize in its diagnosis and treatment.”
Fellow researchers on the multidisciplinary project included Canlan Sun, M.D., Ph.D., and Smita Bhatia, M.D., M.P.H., of the Department of Population Sciences, and Joshua D.I. Ellenhorn, M.D., and Pablo Mojica-Manosa, M.D., of the Department of Surgery.