TUESDAY, Aug. 3, 2004 (HealthDayNews) -- A chemotherapy drug regimen for colon cancer that improved survival rates for five years failed to offer the same benefits 10 years after the initial diagnosis, new research contends.
The finding, an update of a large clinical trial launched in 1977, could lead to a reexamination of chemotherapy regimens, the researchers said. However, they pointed out that the therapies used in the study are no longer recommended by doctors for colon cancer.
"Chemotherapy appeared to reduce the incidence of recurrence and people seemed to live longer [at five years], but at 10 years there was no difference," said Dr. Roy E. Smith, associate professor of human oncology at Drexel University in Philadelphia.
Smith is former director of medical affairs for the National Surgical Adjuvant Breast and Bowel Project, which began the clinical trial evaluating 1,166 patients in 1977 and reported the original results in 1988.
The new findings appear in the Aug. 4 issue of the Journal of the National Cancer Institute.
While the therapy regimens studied in the trial are no longer used, the finding is still valuable, Smith said.
"The bottom line of this paper is, it demonstrates what the natural history of colon cancer is over a 10-year period. You can modulate that history with intervention but not significantly increase survival with treatment that looks like it reduces recurrence [of disease]," he said.
In the original study, 58 percent of patients who had surgery and chemotherapy had no recurrence of colon cancer after five years, while 51 percent of the surgery-only group remained cancer-free after five years. Sixty-seven percent of the surgery/chemotherapy group were still alive after five years, compared to 59 percent of the surgery-only patients.
Also in the original study, 56 percent of those who had immunotherapy and surgery had no recurrence of disease, compared to 51 percent of those who had surgery alone. And 67 percent of those with immunotherapy plus surgery were alive five years later, compared to 59 percent of the surgery-only group.
At 10 years, however, those in the chemotherapy group were no better off in terms of recurrence or overall survival, compared to those who received surgery alone. And the immunotherapy did not prevent tumor relapse, but it did improve the overall survival rates -- 53 percent of the immunotherapy and surgery group survived, compared with 47 percent of the surgery-only group.
It's not clear why immunotherapy didn't prevent cancer recurrence but did help with overall survival, said Dr. Jean Grem, a professor of medicine at the University of Nebraska Medial Center, who wrote an accompanying editorial in the journal.
It might be the immunotherapy favorably affected other problems, such as heart disease, said Grem, an oncologist.
"On the surface, it would look like immunotherapy in the long term made people live longer," Smith said. "When we analyzed the data in detail, immunotherapy reduced somehow the number of noncancer-related deaths [in those getting chemotherapy]."
One key finding of the new study is that most patients who had a recurrence of the cancer had it within the first two or three years after diagnosis, Smith said.
Traditionally, researchers follow cancer patients longer than that. The study findings may persuade investigators to evaluate colon cancer patients and their treatment a bit differently, Smith said.
"In the future, investigators can use a three-year disease-free survival end point rather than five or 10 years to determine the effectiveness of the treatment," he said.
Grem agreed that the study raises "some questions about what are the appropriate endpoints" for evaluating treatments.
Many new colon cancer drugs are in development, she said, adding, "It may be more important to focus on disease-free survival for shorter times."
The finding might also lead to a change in clinical trials for colon cancer, shortening them and the time it takes to publish in medical journals results on the effectiveness of a new treatment, she said.
Grem added that she encourages patients to participate in clinical trials if possible.
"That is the only way we are going to be able to find out if treatments are beneficial or not," she said.
For more on colon cancer, visit the National Cancer Institute.