The recent observation that tumor sidedness is associated with survival in advanced colorectal cancer may not extend to patients with early-stage disease, according to a new study from Canada.
In a population-based cohort study from the Ontario Cancer Registry, there was no association between tumor sidedness and overall survival or cancer-specific survival in patients with stage I to III colon cancer.
“While there seems to be a convincing argument that primary tumor sidedness may have both prognostic and predictive implications for patients with advanced disease, as the authors of the present report have shown, the same may not hold true for early-stage disease,” write the authors of an editorial published with the study online June 8 in JAMA Oncology.
Dr. Safiya Karim from Queen's University Cancer Research Institute in Kingston and colleagues identified 6,365 patients with early-stage colon cancer (49% female). Their median age was 72 years and 52% had right-sided disease. About 18% had stage I disease, 38% stage II, and 43% stage III disease.
Patients with right-sided colon cancer were more likely to be older, female and to have greater comorbidity. Right-sided cancers were more likely to be T4 and poorly differentiated but less likely to be node positive compared with left-sided cancers.
But after adjusting for these factors, there was no difference in long-term survival for right-sided compared with left-sided colon cancer. The hazard ratios were 1.00 (95% CI, 0.92-1.08) for overall survival and 1.00 (95% CI, 0.91-1.10) for cancer-specific survival.
This lack of association with laterality persisted when the survival analyses were restricted to stage III disease, with hazard ratios of 1.03 (95% CI, 0.93-1.14) for overall survival and 1.10 (95% CI, 0.97-1.24) for cancer-specific survival.
Summing up, Dr. Karim and colleagues say their study found “no strong association between disease laterality and outcome of early-stage resected colon cancer. Results of previously published studies are not consistent; therefore, the extent to which disease laterality is prognostic remains uncertain.”
“Future research that can incorporate molecular and genetic elements of disease will provide important insights into how tumor location is associated with patient outcome,” the authors note.
In their editorial, Dr. George Chang from University of Texas MD Anderson Cancer Center in Houston and Dr. Mithat Gonen from Memorial Sloan Kettering Cancer Center in New York make the point that “sidedness in (tumors) that harbor whatever biologic drivers that . . . led to the development of recurrence . . . seems to have a very different interaction than in tumors that are cured by initial treatment.”
“This is another important lesson not only about the molecular heterogeneity of colorectal cancer but also about how these underlying differences affect treatment outcomes of patients at different stages of disease manifestation. Whenever it seems that all has been figured out, it is often humbling to know how much there is still to learn,” they conclude.
The study had no commercial funding. One author disclosed relationships with Amgen and Lilly.
SOURCE: http://bit.ly/2solWvv and http://bit.ly/2sorTbR
JAMA Oncol 2017.