Traditionally, overall survival five years after treatment has been the standard for measuring outcome of adjuvant clinical trials for colon cancer. However, a [meta-analysis](http://www.jco.org/cgi/content/abstract/JCO.2005.01.6071v1) of 18 randomized Phase III clinical trials evaluating adjuvant treatment involving nearly 21,000 patients found a close correlation between lack of recurrence at 3 years and overall survival at 5 years.
Eighty percent (80%) of recurrences occurred within the first 3 years, and 91% of patients who had cancer return within 3 years had died by the 5-year mark. Correlation between disease-free survival at 3 years (DFS) and overall survival at 5 years (OS) was 0.89.
In the pooled data. 12% of recurrences happened in the first year, 14% in the second, 8% in the third, 5% in the fourth, and 3% in the fifth year.
The research team, headed by Dr. Daniel J. Sargent, believes that the study provides evidence for using three-year disease free survival as a surrogate measure for overall survival. This would enable adjuvant research to be completed more quickly, providing critical answers to the best treatment for patients with stage 2 and 3 colon cancer.
In a [*Journal of Clinical Oncology* early release article](http://www.jco.org/cgi/content/abstract/JCO.2005.01.6071v1), published on the internet on October 31, 2005, they concluded:
In patients treated on phase III adjuvant colon clinical trials, DFS and OS are highly correlated, both within patients and across trials. These results suggest that DFS after 3 years of median follow-up is an appropriate end point for adjuvant colon cancer clinical trials of fluorouracil-based regimens, although marginally significant DFS improvements may not translate into significant OS benefits.
In the same issue of the *Journal of Clinical Oncology* Judith Abrahms from the Karmanos Cancer Institute at Wayne State University writes a [commentary](http://www.jco.org/cgi/reprint/JCO.2005.03.6186v1) that warns against over-generalizing the study results to all cancers or to all trials for colon cancer:
Although future studies of FU-based adjuvant therapy
for patients with stages II and III colon cancer may comfortably
use DFS3 years as a primary end point replacing OS5 years,
casual readers are cautioned against generalizing these results
to all colon cancer trials or to cancer clinical trials in
general. These results depend on specific features of the
disease and the current state of diagnosis and therapy.