Secondary Prevention of Colorectal Cancer: Is There an Optimal Follow-up for Patients with Colorectal Cancer?

Co-morbid risk factors and NSAID use among white and black Americans that predicts overall survival from diagnosed colon cancer

Black Americans (BA) have higher incidence and higher mortality rates for colorectal cancers (CRC) as compared to White Americans (WA). While there are several identified risk factors associated with the development of CRC and evidence that high levels of adequate screening can reduce differences in incidence for CRC between BA and WA, there remains little data regarding patient co-morbid contributions towards survival once an individual has CRC. Here we set out to identify patient risk factors that influenced overall survival in a cohort of 293 BA and 348 WA with colon cancer. Amid our cohort, we found that patients’ age, tobacco usage, and pre-diagnosed medical conditions such as hypertension and diabetes were associated with shorter overall survival (OS) from colon cancer. We identified pre-diagnosed hypertension and diabetes among BA were responsible for one-third of the colon cancer mortality disparity compared with WA. We also identified long-term regular use of non-steroidal anti-inflammatory drugs (NSAIDs), including aspirin, was associated with shorter OS from colon cancer among WA >65 years of age, but not younger WA patients or any aged BA patients. Our results raise the importance of not only treating the colon cancer itself, but also taking into consideration co-morbid medical conditions and NSAID usage to enhance patient OS. Further evaluation regarding adequate treatment of co-morbidities and timing of NSAID continuance after cancer therapy will need to be studied.

Causes of Socioeconomic Disparities in Colorectal Cancer and Intervention Framework and Strategies

Colorectal cancer (CRC) disproportionately affects people from low socioeconomic backgrounds and some racial minorities. Disparities in CRC incidence and outcomes might result from differences in exposure to risk factors such as unhealthy diet and sedentary lifestyle; limited access to risk-reducing behaviors such as chemoprevention, screening, and follow-up of abnormal test results; or lack of access to high-quality treatment resources. These factors operate at the individual, provider, health system, community, and policy levels to perpetuate CRC disparities. However, CRC disparities can be eliminated. Addressing the complex factors that contribute to development and progression of CRC with multicomponent, adaptive interventions, at multiple levels of the care continuum, can reduce gaps in mortality. These might be addressed with a combination of health care and community-based interventions and policy changes that promote healthy behaviors and ensure access to high-quality and effective measures for CRC prevention, diagnosis, and treatment. Improving resources and coordinating efforts in communities where people of low socioeconomic status live and work would increase access to evidence-based interventions. Research is also needed to understand the role and potential mechanisms by which factors in diet, intestinal microbiome, and/or inflammation contribute to differences in colorectal carcinogenesis. Studies of large cohorts with diverse populations are needed to identify epidemiologic and molecular factors that contribute to CRC development in different populations.

Genetics and Genetic Biomarkers in Sporadic Colorectal Cancer

Sporadic colorectal cancer (CRC) is a somatic genetic disease in which pathogenesis is influenced by the local colonic environment and the patient's genetic background. Consolidating the knowledge of genetic and epigenetic events that occur with initiation, progression, and metastasis of sporadic CRC has identified some biomarkers that might be utilized to predict behavior and prognosis beyond staging, and inform treatment approaches. Modern next-generation sequencing of sporadic CRCs has confirmed prior identified genetic alterations and has classified new alterations. Each patient's CRC is genetically unique, propelled by 2-8 driver gene alterations that have accumulated within the CRC since initiation. Commonly observed alterations across sporadic CRCs have allowed classification into a (1) hypermutated group that includes defective DNA mismatch repair with microsatellite instability and POLE mutations in ∼15%, containing multiple frameshifted genes and BRAF(V600E); (2) nonhypermutated group with multiple somatic copy number alterations and aneuploidy in ∼85%, containing oncogenic activation of KRAS and PIK3CA and mutation and loss of heterozygosity of tumor suppressor genes, such as APC and TP53; (3) CpG island methylator phenotype CRCs in ∼20% that overlap greatly with microsatellite instability CRCs and some nonhypermutated CRCs; and (4) elevated microsatellite alterations at selected tetranucleotide repeats in ∼60% that associates with metastatic behavior in both hypermutated and nonhypermutated groups. Components from these classifications are now used as diagnostic, prognostic, and treatment biomarkers. Additional common biomarkers may come from genome-wide association studies and microRNAs among other sources, as well as from the unique alteration profile of an individual CRC to apply a precision medicine approach to care.

Biomarker-directed Targeted Therapy in Colorectal Cancer

With advances in the understanding of the biology and genetics of colorectal cancer (CRC), diagnostic biomarkers that may predict the existence or future presence of cancer or a hereditary condition, and prognostic and treatment biomarkers that may direct the approach to therapy have been developed. Biomarkers can be ascertained and assayed from any tissue that may demonstrate the diagnostic or prognostic value, including from blood cells, epithelial cells via buccal swab, fresh or archival cancer tissue, as well as from cells shed into fecal material. For CRC, current examples of biomarkers for screening and surveillance include germline testing for suspected hereditary CRC syndromes, and stool DNA tests for screening average at-risk patients. Molecular biomarkers for CRC that may alter patient care and treatment include the presence or absence of microsatellite instability, the presence or absence of mutant KRAS, BRAF or PIK3CA, and the level of expression of 15-PGDH in the colorectal mucosa. Molecularly targeted therapies and some general therapeutic approaches rely on biomarker information. Additional novel biomarkers are on the horizon that will undoubtedly further the approach to precision or individualized medicine.

EMAST is a Form of Microsatellite Instability That is Initiated by Inflammation and Modulates Colorectal Cancer Progression

DNA mismatch repair (MMR) function is critical for correcting errors coincident with polymerase-driven DNA replication, and its proteins are frequent targets for inactivation (germline or somatic), generating a hypermutable tumor that drives cancer progression. The biomarker for defective DNA MMR is microsatellite instability-high (MSI-H), observed in ~15% of colorectal cancers, and defined by mono- and dinucleotide microsatellite frameshift mutations. MSI-H is highly correlated with loss of MMR protein expression, is commonly diploid, is often located in the right side of the colon, prognosticates good patient outcome, and predicts poor efficacy with 5-fluorouracil treatment. Elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) is another form of MSI at tetranucleotide repeats that has been observed in multiple cancers, but its etiology and clinical relevance to patient care has only been recently illuminated. Specifically, EMAST is an acquired somatic defect observed in up to 60% of colorectal cancers and caused by unique dysfunction of the DNA MMR protein MSH3 (and its DNA MMR complex MutSβ, a heterodimer of MSH2-MSH3), and in particular a loss-of-function phenotype due to a reversible shift from its normal nuclear location into the cytosol in response to oxidative stress and the pro-inflammatory cytokine interleukin-6. Tumor hypoxia may also be a contributor. Patients with EMAST colorectal cancers show diminished prognosis compared to patients without the presence of EMAST in their cancer. In addition to defective DNA MMR recognized by tetranucleotide (and di- and tri-nucleotide) frameshifts, loss of MSH3 also contributes to homologous recombination-mediated repair of DNA double stranded breaks, indicating the MSH3 dysfunction is a complex defect for cancer cells that generates not only EMAST but also may contribute to chromosomal instability and aneuploidy. Areas for future investigation for this most common DNA MMR defect among colorectal cancers include relationships between EMAST and chemotherapy response, patient outcome with aneuploid changes in colorectal cancers, target gene mutation analysis, and mechanisms related to inflammation-induced compartmentalization and inactivation for MSH3.

Usefulness of CEA concentration measurement and classic colonoscopy in follow-up after radical treatment of colorectal cancer

There is always a certain rate of recurrence after radical treatment for cancer and to get on it an early detection of disease set back is crucial.

MATERIAL AND METHODS

Medical data of patients operated on for primarily detected colorectal cancer in years 1993-2002 was retrospectively reviewed. Usefulness of follow-up means such as physical examination, or CEA and endoscopic surveillance was analyzed. All mentioned above were applied to scheduled follow-up (in 3, 6 and 12 month intervals following an operation and annually after that by the year 5).

RESULTS

Complete and reliable data was obtained from 340 out of 502 follow-up intended subjects (67.7%). Elevated CEA was the most frequent predictor of recurrence within non-symptomatic subjects meeting follow-up appointments (60%). The cancer set back diagnosed by means of either physical or endoscopic examinations was the case only in one out of five patients (20.75% and 18.87% respectively). Clinical onset of recurrence making patients meet an unscheduled appointment was found increasing relative risk of nothing-but-palliative option either for them with local set back, or meta-static spread. Relative risk of onset of meta-chronous colonic cancer was significantly higher in patients being affected by synchronous advanced adenoma at time of surgery compared to those with one-fold changes.

CONCLUSIONS

CEA scheduled follow-up after treatment for colorectal cancer CRC seems adequate to provide a good outcome of treatment for recurrent tumors. CRC patients presenting with synchronous advanced adenomas at time of surgery are probably to be under more intensive endoscopic surveillance.