Occult tumor burden contributes to racial disparities in stage-specific colorectal cancer outcomes

Lymph Node Yield in Colon Cancer: Individuals Can Make the Difference

AIM

To investigate the influence of individual surgeons and pathologists on examining an adequate (i.e. ≥10) number of lymph nodes in colon cancer resection specimens.

PATIENTS AND METHODS

The number of lymph nodes was evaluated in surgically treated patients for colon cancer at our hospital from 2008 through 2010, excluding patients who had received neo-adjuvant treatment. The patient group consisted of 156 patients with a median age of 73 (interquartile range (IQR) 63-82 years) and a median of 12 lymph nodes per patient (IQR 8-15). In 106 patients (67.9%), 10 or more nodes were histopathologically examined.

RESULTS

At univariate analysis, the examination of ≥10 nodes was influenced by tumour size (p = 0.05), tumour location (p = 0.015), type of resection (p = 0.034), individual surgeon (p = 0.023), and pathologist (p = 0.005). Neither individual surgeons nor pathologists did statistically and significantly influence the chance of finding an N+ status. Age (p = 0.044), type of resection (p = 0.007), individual surgeon (p = 0.012) and pathologist (p = 0.004) were independent prognostic factors in a multivariate model for finding ≥10 nodes.

CONCLUSION

Though cancer staging was not affected in this study, individual efforts by surgeons and pathologists play a critical role in achieving optimal lymph node yield through conventional methods.

Colorectal cancer disparities: Issues, controversies and solutions

Colorectal cancer (CRC) is the second leading cause of cancer related deaths in the United States. There are significant differences in CRC incidence and mortality by race with the highest burden occurring among blacks. The underlying factors contributing to CRC disparities are multiple and complex. Studies have suggested that a higher prevalence of putative risk factors for CRC, limited access to healthcare services, lower utilization of healthcare resources and increased biological susceptibilities contribute to this disparity by race. This article reviews the factors associated with the disproportionally higher burden of CRC among blacks; addresses the controversies regarding the age to begin CRC screening and the screening modality to use for blacks; and proffers solutions to eliminate CRC disparity by race.

Disparities in survival improvement for metastatic colorectal cancer by race/ethnicity and age in the United States

PURPOSE

Previous studies documented significant increase in overall survival for metastatic colorectal cancer (CRC) since the late 1990s coinciding with the introduction and dissemination of new treatments. We examined whether this survival increase differed across major racial/ethnic populations and age groups.

METHODS

We identified patients diagnosed with primary metastatic colorectal cancer during 1992-2009 from 13 population-based cancer registries of the National Cancer Institute's Surveillance, Epidemiology, and End Results Program, which cover about 14 % of the US population. The 5-year cause-specific survival rates were calculated using SEER*Stat software.

RESULTS

From 1992-1997 to 2004-2009, 5-year cause-specific survival rates increased significantly from 9.8 % (95 % CI 9.2-10.4) to 15.7 % (95 % CI 14.7-16.6) in non-Hispanic whites and from 11.4 % (95 % CI 9.4-13.6) to 17.7 % (95 % CI 15.1-20.5) in non-Hispanic Asians, but not in non-Hispanic blacks [from 8.6 % (95 % CI 7.2-10.1) to 9.8 % (95 % CI 8.1-11.8)] or Hispanics [from 14.0 % (95 % CI 11.8-16.3) to 16.4 % (95 % CI 14.0-19.0)]. By age group, survival rates increased significantly for the 20-64-year age group and 65 years or older age group in non-Hispanic whites, although the improvement in the older non-Hispanic whites was substantially smaller. Rates also increased in non-Hispanic Asians for the 20-64-year age group although marginally nonsignificant. In contrast, survival rates did not show significant increases in both younger and older age groups in non-Hispanic blacks and Hispanics.

CONCLUSION

Non-Hispanic blacks, Hispanics, and older patients diagnosed with metastatic CRC have not equally benefitted from the introduction and dissemination of new treatments.

Evidence-based Guidelines for Precision Risk Stratification-Based Screening (PRSBS) for Colorectal Cancer: Lessons learned from the US Armed Forces: Consensus and Future Directions

Colorectal cancer (CRC) is the third most common cause of cancer-related death in the United States (U.S.), with estimates of 143,460 new cases and 51,690 deaths for the year 2012. Numerous organizations have published guidelines for CRC screening; however, these numerical estimates of incidence and disease-specific mortality have remained stable from years prior. Technological, genetic profiling, molecular and surgical advances in our modern era should allow us to improve risk stratification of patients with CRC and identify those who may benefit from preventive measures, early aggressive treatment, alternative treatment strategies, and/or frequent surveillance for the early detection of disease recurrence. To better negotiate future economic constraints and enhance patient outcomes, ultimately, we propose to apply the principals of personalized and precise cancer care to risk-stratify patients for CRC screening (Precision Risk Stratification-Based Screening, PRSBS). We believe that genetic, molecular, ethnic and socioeconomic disparities impact oncological outcomes in general, those related to CRC, in particular. This document highlights evidence-based screening recommendations and risk stratification methods in response to our CRC working group private-public consensus meeting held in March 2012. Our aim was to address how we could improve CRC risk stratification-based screening, and to provide a vision for the future to achieving superior survival rates for patients diagnosed with CRC.

Molecular staging of node negative patients with colorectal cancer

Metastatic disease is the principle cause of death from colorectal cancer. In that context, the most significant indicator of overall survival and therapeutic response to adjuvant chemotherapy is the presence of metastatic tumor cells in regional lymph nodes. Although histopathologic analysis of lymph nodes is central to all colorectal cancer staging paradigms, its prognostic and predictive value is limited. Indeed, about 30% of patients with histopathology-negative lymph nodes (pN0) die from metastatic disease, reflected by microscopic lymph node metastases that are overlooked by standard techniques. These unrecognized tumor cells are especially important when considering racial disparities in outcomes in colorectal cancer patients, where blacks with lymph node-negative disease have the largest discrepancies in outcomes, with more than 40% excess mortality compared to Caucasian patients. However, the significance of tumor cells in regional lymph nodes remains uncertain, and approximately 50% of colorectal cancer patients with nodal metastases detected by histopathology remain free of recurrent disease. Accurate identification of occult metastases in regional lymph nodes, and defining their value as prognostic markers of recurrence risk and predictive markers of response to adjuvant chemotherapy remains one challenge in the management of colorectal cancer patients. Guanylyl cyclase C (GUCY2C), a receptor which is expressed primarily in intestinal cells normally, but is universally over-expressed by colorectal cancer cells, has been validated to detect prognostically significant occult metastases using quantitative RT-PCR (RT-qPCR). Biomarker validation was achieved through a prospective, multicenter, blinded clinical trial. In that trial, occult tumor burden estimated across all regional lymph nodes by GUCY2C RT-qPCR predicted clinical outcomes, identifying node-negative patients with a low (near zero) risk, and those with >80% risk, of developing disease recurrence. Moreover, there was disproportionately higher occult tumor burden in black, compared to white, patients which contributes to racial disparities in outcomes in colorectal cancer. The diagnostic paradigm quantifying occult tumor burden using GUCY2C qRT-PCR is positioned to reduce racial disparities in colorectal cancer mortality.

Guanylyl cyclase C as a biomarker in colorectal cancer

While histologic assessment of nodes is a component of all colon cancer staging paradigms, approximately 30% of patients with histology-negative nodes (pN0) die of disseminated disease reflected by occult nodal metastases. Undetected metastases are particularly important when considering racial disparities in colon cancer, where black subjects with pN0 disease exhibit the greatest differences in outcomes, with >40% excess mortality. Recently, guanylyl cyclase C (GCC), a protein normally restricted to intestinal cells, but universally expressed by colorectal cancer cells, was validated for detecting occult metastases. Indeed, occult tumor burden across regional lymph nodes estimated by GCC quantitative reverse transcription PCR identifies pN0 patients with near zero risk, and those with >80% risk, of unfavorable outcomes. Disproportionately high occult tumor burden in black patients underlies racial disparities in stage-specific mortality. These studies position the platform encompassing quantification of occult tumor burden by GCC quantitative reverse transcription PCR for translation, as a detect-treat paradigm to reduce racial disparities in colon cancer mortality.

GUCY2C molecular staging personalizes colorectal cancer patient management

While the most significant prognostic and predictive marker in the management of colorectal cancer patients is cancer cells in regional lymph nodes, approximately 30% of patients whose lymph nodes are ostensibly free of tumor cells by histopathology ultimately develop recurrent disease reflecting occult metastases. Molecular techniques utilizing highly specific markers and ultra-sensitive detection technologies have emerged as powerful staging platforms to establish prognosis and predict responsiveness to chemotherapy in colorectal cancer patients. This review describes the evolution of the tumor suppressor GUCY2C as a prognostic and predictive molecular biomarker that quantifies occult tumor burden in regional lymph nodes for staging patients with colorectal cancer.

Analytic lymph node number establishes staging accuracy by occult tumor burden in colorectal cancer

BACKGROUND AND OBJECTIVES

Recurrence in lymph node-negative (pN0) colorectal cancer suggests the presence of undetected occult metastases. Occult tumor burden in nodes estimated by GUCY2C RT-qPCR predicts risk of disease recurrence. This study explored the impact of the number of nodes analyzed by RT-qPCR (analytic) on the prognostic utility of occult tumor burden.

METHODS

Lymph nodes (range: 2-159) from 282 prospectively enrolled pN0 colorectal cancer patients, followed for a median of 24 months (range: 2-63), were analyzed by GUCY2C RT-qPCR. Prognostic risk categorization defined using occult tumor burden was the primary outcome measure. Association of prognostic variables and risk category were defined by multivariable polytomous and semi-parametric polytomous logistic regression.

RESULTS

Occult tumor burden stratified this pN0 cohort into categories of low (60%; recurrence rate (RR) = 2.3% [95% CI 0.1-4.5%]), intermediate (31%; RR = 33.3% [23.7-44.1%]), and high (9%; RR = 68.0% [46.5-85.1%], P < 0.001) risk of recurrence. Beyond race and T stage, the number of analytic nodes was an independent marker of risk category (P < 0.001). When >12 nodes were analyzed, occult tumor burden almost completely resolved prognostic risk classification of pN0 patients.

CONCLUSIONS

The prognostic utility of occult tumor burden assessed by GUCY2C RT-qPCR is dependent on the number of analytic lymph nodes.