Home Advisory Panel           Conferences & Events          
Mortality by Stage for Right- Versus Left-Sided Colon Cancer
Scope of the Problem


Previously published studies have reported increased mortality rates for patients diagnosed with right-sided colon cancers; however these reports had inconsistent results by stage and demonstrated limited adjustment for individual patient characteristics. The incidence of right-sided colon tumors has increased; right-sided colon tumors have been noted to have significant differences versus those occurring in the left side of the colon (Meguid, et al. 2008). These differences include: higher likelihood of being exophytic, diploid, and higher incidences of mucinous histology, high microsatellite instability, and CpG island methylation (Bufill, et al. 1990). Patients presenting with left-sided tumors frequently have infiltrating lesions, may present with obstructive symptoms, display chromosomal instability, and higher aneuploidy tumors; analysis has also demonstrated a difference in the gene expressions between the two presentations. Despite these differences, it is not clear if the location of the tumor and its biologic differences affect mortality for patients with colon cancer and this uncertainty is further complicated by previously published studies with conflicting results. Therefore, a recent study published by Weiss and colleagues (2011) sought to examine the relationship between colon cancer location and five year mortality by stage.


Study Facts


  • Medicare beneficiaries from 1992 to 2005 with American Joint Commission of Cancer (AJCC) stages I to III primary adenocarcinoma of the colon who underwent surgery with curative intent were identified through Surveillance, Epidemiology, and End Results (SEER) – Medicare data
  • Using Cox proportional hazards regression, adjusted hazard rations (HRs) and 95% confidence intervals (CI) were obtained for predictors of all cause five year mortality
  • The results of the study demonstrated that out of 53,801 patients, 67% had right-sided colon cancer; these patients were more likely to be older, women, diagnosed at a more advanced stage, and have more poorly differentiated tumors
  • The primary explanatory variable was tumor location; basic patient-related variables included demographic data and disease-related variables, such as poor prognostic features, year of diagnosis, presentation with intestinal obstruction or perforation, higher stage, poor histology and fewer than 12 lymph nodes examined at surgery
  • The most significant patient-related predictors of increased mortality were older age, male sex, and being widowed or single, separated, or divorced versus married
  • Adjusted Cox regression analysis showed no significant difference in mortality between right- and left-sided tumors for all stages combined (HR, 1.01; 95% CI, 0.98 to 1.04, P = 0.598) or for stage I cancers (HR, 0.95; 95% CI, 0.88 to 1.03; P = 0.211)
  • Patients with stage II right-sided tumors had lower mortality than left-sided tumors (HR, 0.92; 95% CI, 0.87 to 0.97; P = 0.001)
  • Stage III right-sided tumors had higher mortality (HR, 1.12; 95% CI, 1.06 to 1.18; P < 0.001) (Weiss, et al. 2011)
The study authors concluded that no overall difference was noted in five year mortality between right- and left-sided colon cancers when the data were adjusted for multiple patient, disease, comorbidity and treatment variables; however, with stage II disease, right-sided cancers conferred lower mortality, and within stage III cancers, right-sided cancers had higher mortality (Weiss, et al. 2011).


ManageCRC.com Commentary


After controlling for multiple variables, there was no overall difference in five year mortality between patients presenting with right- or left-sided tumors. These data are markedly different from previously published studied reporting higher risk of mortality in patients presenting with right-sided tumors (Meguid et al., 2008). As discussed in the Weiss (2011) study, the differences in study results are probably due to increased knowledge regarding tumor biology, and specifically the data on microsatellite instability (MSI) status. MSI is most often present in right-sided colon cancers, with less than 5% of left sided cancers displaying MSI (conferring an improved stage profile) (Iacopetta, 2002). Researchers continue to expand the knowledge base regarding tumor biology and the improvements in survival that specific aspects can confer; this study is an example of how important additional variables can be when determining mortality related to colon cancer. Continued research will add to the body of knowledge regarding tumor biology and physical location.


References


Bufill, J.A. (1990). Colorectal cancer: Evidence for distinct genetic categories based on proximal or distal tumor location. Annals of Internal Medicine, 113, 779-788. Link to abstract: http://www.ncbi.nlm.nih.gov/pubmed/2240880


Iacopetta, B. (2002). Are there two sides to colorectal cancer? International Journal of Cancer, 101, 403-408. doi:10.1002/ijc.10635   Link to free full text: http://onlinelibrary.wiley.com/doi/10.1002/ijc.10635/full


Meguid, R.A., Slidell, M.B., Wolfgang, C.L., Chang, D.C., & Ahuja, N. (2008). Is there a difference in survival between right-versus left-sided colon cancers? Annals of Surgical Oncology, 15, 2388-2394. doi: 10.1245/s10434-008-0015-y     Link to free full text: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3072702/pdf/nihms280426.pdf


Weiss, J.M., Pfau, P.R., O’Connor, E.S., King, J., LoConte, N., Kennedy, G.,…Smith, M.A. (2011). Mortality by stage for right-versus left-sided colon cancer: Analysis of surveillance, epidemiology, and end results – Medicare date. Journal of Clinical Oncology. Published online before print October 3 2011. doi:10.1200/JCO.2011.36.4414  Link to abstract http://www.ncbi.nlm.nih.gov/pubmed?term=weiss%2C%20pfau%2C%20o'connor   
 


Article Created On : 11/18/2011 10:29:05 AM             Article Updated On : 11/18/2011 10:29:05 AM