Even though patients with metastatic colorectal cancer younger than age 50 tend to be more fit and receive more intensive treatment than older patients, survival for both groups is roughly the same, according to a study published by Lipsyc-Sharf et al in the Journal of the National Cancer Institute.
The study’s researchers said the results are somewhat surprising, as younger patients, who usually have fewer complicating health factors, might be expected to survive longer than older patients.
“As a group, younger patients are more physically active, have higher performance status, and are better able to perform the activities of daily living than older patients. They also tend to be treated with higher doses of therapy and have less severe side effects,” said the study’s senior author Kimmie Ng, MD, MPH, Director of the Young-Onset Colorectal Cancer Center at Dana-Farber Cancer Institute. “This is the first study to compare survival in younger vs older patients participating in a clinical trial of treatment for metastatic colorectal cancer.”
Kimmie Ng, MD, MPH
The study drew on data from the CALGB/SWOG 80405 clinical trial, which tested a combination of chemotherapy and biologic therapy in patients with metastatic colorectal cancer. Researchers compared survival times in 514 trial participants who were younger than age 50 with the survival of 1,812 patients older than 50.
“We found no significant difference in overall survival between the two groups,” said first study author Marla Lipsyc-Sharf, MD, also of Dana-Farber Cancer Institute.
The median survival for patients with young-onset colorectal cancer was 27.1 months vs 26.1 months for the older-onset group. Progression-free survival was also similar between the two groups: 10.9 months in the younger patients vs 10.6 months in the older ones.
Confounding expectations even further, the investigators found that patients younger than age 35 had the shortest median overall survival of any age group: about 22 months. Because the study included relatively few patients younger than 35, the difference is not considered statistically significant, researchers said, but it aligns with previous research suggesting that very young patients have worse outcomes.
Significance of the Findings
The findings underscore that there is still much to be learned about young-onset colorectal cancer. Cases are markedly on the rise: between 2000 and 2013, incidence of the disease in people younger than age 50 increased by approximately 22%, even as overall incidence of colorectal cancer has declined. Yet despite a wellspring of new research, no definitive cause for the increase has been found.
“If current trends hold, colorectal cancer is projected to be the second-leading cancer and leading cause of cancer death in patients aged 20 to 49 [years] by the year 2040,” Dr. Lipsyc-Sharf stated. “It is important to understand survival in this population in order to develop tailored treatments.”
The finding that younger patients fare no better than older patients, despite having several factors in their favor, might suggest that colorectal cancer is more aggressive at an earlier age. However, there’s no conclusive evidence that that is the case.
“Research has yet to identify consistent molecular differences in the colorectal cancer cells of younger patients and older patients,” Dr. Lipsyc-Sharf noted.
Current studies also are exploring whether differences in the intestinal microbiome of younger and older patients might explain the increased incidence of early-onset colorectal cancer.
Disclosure: This work was supported by the National Cancer Institute, the Department of Defense, the Project P Fund, and P30 CA008748. It was also supported in part by funds from Bristol Myers Squibb, Genentech, Pfizer, and Sanofi. For full disclosures of the study authors, visit academic.oup.com/jnci.The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.