Prognostic and predictive roles of high-degree microsatellite instability in colon cancer: a National Cancer Institute-National Surgical Adjuvant Breast and Bowel Project Collaborative Study

Association of obesity with DNA mismatch repair status and clinical outcome in patients with stage II or III colon carcinoma participating in NCCTG and NSABP adjuvant chemotherapy trials

PURPOSE

Although the importance of obesity in colon cancer risk and outcome is recognized, the association of body mass index (BMI) with DNA mismatch repair (MMR) status is unknown.

PATIENTS AND METHODS

BMI (kg/m(2)) was determined in patients with TNM stage II or III colon carcinomas (n = 2,693) who participated in randomized trials of adjuvant chemotherapy. The association of BMI with MMR status and survival was analyzed by logistic regression and Cox models, respectively.

RESULTS

Overall, 427 (16%) tumors showed deficient MMR (dMMR), and 630 patients (23%) were obese (BMI ≥ 30 kg/m(2)). Obesity was significantly associated with younger age (P = .021), distal tumor site (P = .012), and a lower rate of dMMR tumors (10% v 17%; P < .001) compared with normal weight. Obesity remained associated with lower rates of dMMR (odds ratio, 0.57; 95% CI, 0.41 to 0.79; P < .001) after adjusting for tumor site, stage, sex, and age. Among obese patients, rates of dMMR were lower in men compared with women (8% v 13%; P = .041). Obesity was associated with higher recurrence rates (P = .0034) and independently predicted worse disease-free survival (DFS; hazard ratio [HR], 1.37; 95% CI, 1.14 to 1.64; P = .0010) and overall survival (OS), whereas dMMR predicted better DFS (HR, 0.59; 95% CI, 0.47 to 0.74; P < .001) and OS. The favorable prognosis of dMMR was maintained in obese patients.

CONCLUSION

Colon cancers from obese patients are less likely to show dMMR, suggesting obesity-related differences in the pathogenesis of colon cancer. Although obesity was independently associated with adverse outcome, the favorable prognostic impact of dMMR was maintained among obese patients.

Mismatch repair status in sporadic colorectal cancer: immunohistochemistry and microsatellite instability analyses

BACKGROUND AND AIM

The aim of the present study was to evaluate associations between mismatch repair (MMR) status and clinicopathological characteristics and prognosis using immunohistochemistry (IHC) and microsatellite instability (MSI) analyses in a prospective cohort of a large number of accumulated samples.

METHODS

Tumor tissue samples obtained during curative surgery (n = 2028) were analyzed using both MLH1/MSH2 IHC and MSI assays. Clinicopathological parameters and survival outcomes were compared according to IHC and MSI results. The median follow-up period was 43 months (range: 1-85 months).

RESULTS

IHC identified 207 tumor samples (10.2%) with a loss of either MLH1 or MSH2 expression. The MSI analysis identified 203 tumor samples (10%) with high-frequency MSI (MSI-H). Patients with MMR defects were younger, and had tumors characterized by right-colon predilection; large-size, infrequent lymph node metastasis; poorly-differentiated or mucinous histology, and synchronous adenomas (P < 0.001-0.008). Patients with MSI-H status had higher 4-year disease-free survival rates than patients with microsatellite stable status (90.8% vs 80.6%, P = 0.001). A multivariate analysis showed that MSI-H status was a good prognostic factor for recurrence (hazard ratio: 0.48, 95% confidence interval: 0.30-0.83, P = 0.007).

CONCLUSIONS

Patients with MMR defects had distinct clinicopathological characteristics, including a lower risk of recurrence. IHC and MSI analyses provided complementary information regarding specific clinicopathological parameters and prognosis.

Predictive and prognostic molecular markers for cancer medicine

Over the last 10 years there has been an explosion of information about the molecular biology of cancer. A challenge in oncology is to translate this information into advances in patient care. While there are well-formed routes for translating new molecular information into drug therapy, the routes for translating new information into sensitive and specific diagnostic, prognostic and predictive tests are still being developed. Similarly, the science of using tumor molecular profiles to select clinical trial participants or to optimize therapy for individual patients is still in its infancy. This review will summarize the current technologies for predicting treatment response and prognosis in cancer medicine, and outline what the future may hold. It will also highlight the potential importance of methods that can integrate molecular, histopathological and clinical information into a synergistic understanding of tumor progression. While these possibilities are without doubt exciting, significant challenges remain if we are to implement them with a strong evidence base in a widely available and cost-effective manner.

The differential impact of microsatellite instability as a marker of prognosis and tumour response between colon cancer and rectal cancer

BACKGROUND

Microsatellite instability (MSI) is a distinct molecular phenotype of colorectal cancer related to prognosis and tumour response to 5-fluorouracil (5-FU)-based chemotherapy. We investigated the differential impact of MSI between colon and rectal cancers as a marker of prognosis and chemotherapeutic response.

METHODS

PCR-based MSI assay was performed on 1125 patients. Six hundred and sixty patients (58.7%) had colon cancer and 465 patients (41.3%) had rectal cancer.

RESULTS

Among 1125 patients, 106 (9.4%) had high-frequency MSI (MSI-H) tumours. MSI-H colon cancers (13%) had distinct phenotypes including young age at diagnosis, family history of colorectal cancer, early Tumor, Node, Metastasis (TNM) stage, proximal location, poor differentiation, and high level of baseline carcinoembryonic antigen (CEA), while MSI-H rectal cancers (4.3%) showed similar clinicopathological characteristics to MSS/MSI-L tumours except for family history of colorectal cancer. MSI-H tumours were strongly correlated with longer disease free survival (DFS) (P=0.005) and overall survival (OS) (P=0.009) than MSS/MSI-L tumours in colon cancer, while these positive correlations were not observed in rectal cancers. The patients with MSS/MSI-L tumours receiving 5-FU-based chemotherapy showed good prognosis (P=0.013), but this positive association was not observed in MSI-H (P=0.104).

CONCLUSION

These results support the use of MSI status as a marker of prognosis and response to 5-FU-based chemotherapy in patients with colon cancers. Further study is mandatory to evaluate the precise role of MSI in patients with rectal cancers and the effect of 5-FU-based chemotherapy in MSI-H tumours.

The role of Cathepsin S as a marker of prognosis and predictor of chemotherapy benefit in adjuvant CRC: a pilot study

Background:

The aim of this pilot retrospective study was to investigate the immunohistochemical expression of Cathepsin S (CatS) in three cohorts of colorectal cancer (CRC) patients (n=560).

Methods:

Prevalence and association with histopathological variables were assessed across all cohorts. Association with clinical outcomes was investigated in the Northern Ireland Adjuvant Chemotherapy Trial cohort (n=211), where stage II/III CRC patients were randomised between surgery-alone or surgery with adjuvant fluorouracil/folinic acid (FU/FA) treatment.

Results:

Greater than 95% of tumours had detectable CatS expression with significantly increased staining in tumours compared with matched normal colon (P>0.001). Increasing CatS was associated with reduced recurrence-free survival (RFS; P=0.03) among patients treated with surgery alone. Adjuvant FU/FA significantly improved RFS (hazard ratio (HR), 0.33; 95% CI, 0.12–0.89) and overall survival (OS; HR, 0.25; 95% CI, 0.08–0.81) among 36 patients with high CatS. Treatment did not benefit the 66 patients with low CatS, with a RFS HR of 1.34 (95% CI, 0.60–3.19) and OS HR of 1.33 (95% CI, 0.56–3.15). Interaction between CatS and treatment status was significant for RFS (P=0.02) and OS (P=0.04) in a multivariate model adjusted for known prognostic markers.

Conclusion:

These results signify that CatS may be an important prognostic biomarker and predictive of response to adjuvant FU/FA in CRC.

Predictive molecular classifiers in colorectal cancer

The introduction of predictive molecular markers has radically enhanced the identification of which patients may benefit from a given treatment. Despite recent controversies, KRAS mutation is currently the most recognized molecular predictive marker in colorectal cancer (CRC), predicting efficacy of anti-epidermal growth factor receptor (anti-EGFR) antibodies. However, other relevant markers have been reported and claimed to identify patients that will benefit from anti-EGFR therapies. This group of markers includes BRAF mutations, PI3KCA mutations, and loss of PTEN expression. Similarly, molecular markers for cytotoxic agents' efficacy also may predict outcome in patients with CRC. This review aims to summarize the most important predictive molecular classifiers in patients with CRC and further discuss any inconsistent or conflicting findings for these molecular classifiers.

TGFBR2 and BAX mononucleotide tract mutations, microsatellite instability, and prognosis in 1072 colorectal cancers

BACKGROUND

Mononucleotide tracts in the coding regions of the TGFBR2 and BAX genes are commonly mutated in microsatellite instability-high (MSI-high) colon cancers. The receptor TGFBR2 plays an important role in the TGFB1 (transforming growth factor-β, TGF-β) signaling pathway, and BAX plays a key role in apoptosis. However, a role of TGFBR2 or BAX mononucleotide mutation in colorectal cancer as a prognostic biomarker remains uncertain.

METHODOLOGY/PRINCIPAL FINDINGS

We utilized a database of 1072 rectal and colon cancers in two prospective cohort studies (the Nurses' Health Study and the Health Professionals Follow-up Study). Cox proportional hazards model was used to compute mortality hazard ratio (HR), adjusted for clinical, pathological and molecular features including the CpG island methylator phenotype (CIMP), LINE-1 methylation, and KRAS, BRAF and PIK3CA mutations. MSI-high was observed in 15% (162/1072) of all colorectal cancers. TGFBR2 and BAX mononucleotide mutations were detected in 74% (117/159) and 30% (48/158) of MSI-high tumors, respectively. In Kaplan-Meier analysis as well as univariate and multivariate Cox regression analyses, compared to microsatellite stable (MSS)/MSI-low cases, MSI-high cases were associated with superior colorectal cancer-specific survival [adjusted HR, 0.34; 95% confidence interval (CI), 0.20-0.57] regardless of TGFBR2 or BAX mutation status. Among MSI-high tumors, TGFBR2 mononucleotide mutation was associated with CIMP-high independent of other variables [multivariate odds ratio, 3.57; 95% CI, 1.66-7.66; p = 0.0011].

CONCLUSIONS

TGFBR2 or BAX mononucleotide mutations are not associated with the patient survival outcome in MSI-high colorectal cancer. Our data do not support those mutations as prognostic biomarkers (beyond MSI) in colorectal carcinoma.

Use of capecitabine in management of early colon cancer

Capecitabine (Xeloda^®, Roche, Basel, Switzerland) is a pro-drug of 5-fluorouracil (5-FU), and it is converted to 5-FU in the cancer cell by enzymatic degradation. The role of capecitabine in colorectal cancer has evolved in the last 15 years. In early trials in the metastatic setting, capecitabine has shown superior response rates compared with those achieved with 5-FU (Mayo Clinic regimen) (26% vs 17%), with equivalent progression-free survival and overall survival. In the adjuvant setting, the Xeloda in Adjuvant Colon Cancer Therapy (X-ACT) trial demonstrated that capecitabine as a single agent led to improvement in relapse-free survival (hazard ratio: 0.86, 95% confidence interval: 0.74–0.99, P = 0.04) and was associated with significantly fewer adverse events than 5-FU plus leucovorin (LV, folinic acid). On the basis of the X-ACT trial, capecitabine was approved by the United States Food and Drug Administration, the National Institute for Clinical Excellence, and the Scottish Medicines Consortium as monotherapy for the adjuvant treatment of stage III colon cancer. The next step was to incorporate capecitabine into combination therapy. The XELOXA trial studied the combination of capecitabine and oxaliplatin (XELOX) vs 5-FU/LV and demonstrated 5-year disease-free survival of 66% for XELOX, compared with 60% for 5-FU/LV. The toxicity profile was also quite comparable in the two arms. So both the single agent use of capecitabine as well as in combination with oxaliplatin can be considered as part of the standard of care in management of early colon cancer in appropriately selected patient groups.

Tumour Genetics and Genomics to Personalise Cancer Treatment

Personalising cancer treatment to optimise therapeutic efficacy while minimising exposure to the toxicities of ineffective drugs is the holy grail of medical oncology. Clinical parameters and conventional histopathological characterisations of cancers are no longer adequate to guide the practising oncologists in treatment planning. The explosion of knowledge in cancer molecular biology has led to the availability of tumour-specific molecules that serve as predictive and prognostic markers. In breast cancer, HER-2 positivity is a good predictor for success of anti-HER-2 trastuzumab monoclonal antibody therapy. K-ras mutational status predicts the likelihood of response to anti-EGFR monoclonal antibodies in advanced colorectal cancers. Similarly, EGFR mutational status in pulmonary adenocarcinoma is highly predictive for responses or otherwise to tyrosine kinase inhibitors. Notwithstanding our deeper understanding of tumour biology and the availability of predictive and prognostic laboratory tools, we are still far from achieving our dream of the perfect personalised cancer treatment, as each tumour in a particular patient is unique to itself. A much coveted, real-time, anti-tumour drug sensitivity testing in the future may one day pave the way for truly treating the right tumour with the right drug in the right patient. Key words: Personalised cancer treatment, Predictive markers, Prognostic markers

Cancer immunology--analysis of host and tumor factors for personalized medicine

Immune cells in the tumor microenvironment have an important role in regulating tumor progression. Therefore, stimulating immune reactions to tumors can be an attractive therapeutic and prevention strategy. Cancer cells and host cells constantly interact with each other in the tumor microenvironment; thus, cancer immunology is an interdisciplinary area where integrated analysis of both host and tumor factors is needed. Cancer represents a heterogeneous group of diseases with different genetic and epigenetic alterations; therefore, molecular classification of cancer (for example lung, prostate and breast cancers) is an important component in clinical decision making. However, most studies on antitumor immunity and clinical outcome lack analysis of tumor molecular biomarkers. In this Review, we discuss colorectal cancer as a prototypical example of cancer. Common molecular classifiers of colon cancer include KRAS, BRAF and PIK3CA mutations, microsatellite instability, LINE-1 methylation, and CpG island methylator phenotype. Since tumor molecular features and immune reactions are inter-related, a comprehensive assessment of these factors is critical. Examining the effects of tumor-host interactions on clinical outcome and prognosis represents an evolving interdisciplinary field of molecular pathological epidemiology. Pathological immunity evaluation may provide information on prognosis and help identify patients who are more likely to benefit from immunotherapy.

Challenges in the management of stage II colon cancer

Approximately one third of patients diagnosed with early-stage colon cancer will present with lymph node involvement (stage III) and about one quarter with transmural bowel wall invasion but negative lymph nodes (stage II). Adjuvant chemotherapy targets micrometastatic disease to improve disease-free (DFS) and overall survival (OS). While beneficial for stage III patients, the role of adjuvant chemotherapy is unestablished in stage II disease. This likely relates to the improved outcome of these patients, and the difficulties in developing studies with sufficient power to document benefit in this patient population. However, recent investigation also suggests that molecular differences may exist between stage II and III cancers and within stage II patients. Validated pathologic prognostic markers are useful at identifying stage II patients at high risk for recurrence for whom the benefit from adjuvant chemotherapy may be greater. Such high-risk features include higher T stage (T4 v T3), suboptimal lymph node retrieval, presence of lymphovascular invasion, bowel obstruction, or bowel perforation, and poorly differentiated histology. However, for the majority of patients who do not carry any of these adverse features and are classified as "average-risk" stage II patients, the benefit of adjuvant chemotherapy remains unproven. Emerging understanding of the underlying biology of stage II colon cancer has identified molecular markers that may change this paradigm and improve our risk assessment and treatment choices for stage II disease. Assessment of microsatellite stability (MSI), which serves as a marker for DNA mismatch repair (MMR) system function, has emerged as a useful tool for risk stratification of patients with stage II colon cancer. Patients with high frequency of MSI have been shown to have increased OS and limited benefit from 5-fluorouracil (5-FU)-based chemotherapy. Additional research is necessary to clearly define the most appropriate way to use this marker and others in routine clinical practice.

Adjuvant chemotherapy for stage II colon cancer with poor prognostic features

PURPOSE

Adjuvant chemotherapy is typically considered for patients with stage II colon cancer characterized by poor prognostic features, including obstruction, perforation, emergent admission, T4 stage, resection of fewer than 12 lymph nodes, and poor histology. Despite frequent use, the survival advantage conferred on patients with stage II disease by chemotherapy is yet unproven. We sought to determine the overall survival benefit of chemotherapy among patients with stage II colon cancer having poor prognostic features.

PATIENTS AND METHODS

A total of 43,032 Medicare beneficiaries who underwent colectomy for stage II and III primary colon adenocarcinoma diagnosed from 1992 to 2005 were identified from the Surveillance, Epidemiology, and End Results (SEER) -Medicare database. χ(2) and two-way analysis of variance were used to assess differences in patient- and disease-related characteristics. Five-year overall survival was examined using Kaplan-Meier survival analysis and Cox proportional hazards regression with propensity score weighting.

RESULTS

Of the 24,847 patients with stage II cancer, 75% had one or more poor prognostic features. Adjuvant chemotherapy was received by 20% of patients with stage II disease and 57% of patients with stage III disease. After adjustment, 5-year survival benefit from chemotherapy was observed only for patients with stage III disease (hazard ratio[HR], 0.64; 95% CI, 0.60 to 0.67). No survival benefit was observed for patients with stage II cancer with no poor prognostic features (HR, 1.02; 95% CI, 0.84 to 1.25) or stage II cancer with any poor prognostic features (HR, 1.03; 95% CI, 0.94 to 1.13).

CONCLUSION

Among Medicare patients identified with stage II colon cancer, either with or without poor prognostic features, adjuvant chemotherapy did not substantially improve overall survival. This lack of benefit must be considered in treatment decisions for similar older adults with colon cancer.

Prognostic and predictive impact of DNA mismatch repair in the management of colorectal cancer

Colorectal cancers develop via two major pathways that include chromosomal instability and microsatellite instability. Microsatellite instability occurs due to deficient DNA mismatch repair (MMR), which can be caused by epigenetic silencing of the MLH1 MMR gene in sporadic colorectal cancers or germline mutations in MMR genes that result in Lynch syndrome. While the molecular origin of deficient MMR differs, sporadic and Lynch syndrome tumors share similar pathological features and have a more favorable stage-adjusted prognosis compared with MMR-proficient cases. While controversy remains, there is evidence to suggest that deficient MMR may predict a lack of benefit from 5-fluorouracil-based adjuvant chemotherapy. The focus of this article is on the MMR phenotype and its prognostic and predictive implications for the management of patients with colorectal cancer.

Inherited colorectal cancer syndromes

Colorectal cancer is common in the Western world; ~5% of individuals diagnosed with colorectal cancer have an identifiable inherited genetic predisposition to this malignancy. Genetic testing and rational clinical management recommendations currently exist for the management of individuals with a variety of colorectal cancer syndromes, including hereditary nonpolyposis colorectal cancer (HNPCC, also known as Lynch syndrome), familial adenomatous polyposis (FAP), MYH-associated polyposis (MAP), and the hamartomatous polyposis syndromes (Peutz-Jeghers, juvenile polyposis, and Cowden disease). In addition to colorectal neoplasia, these syndromes frequently predispose carriers to a variety of extracolonic cancers. The elucidation of the genetic basis of several colorectal cancer predisposition syndromes over the past two decades has allowed for better management of individuals who are either affected with, or at-risk for inherited colorectal cancer syndromes. Appropriate multidisciplinary management of these individuals includes genetic counseling, genetic testing, clinical screening, and treatment recommendations.

Adjuvant Chemotherapy for Stage II Colon Cancer: The Role of Molecular Markers in Choosing Therapy

The optimal adjuvant treatment for stage II colon cancer remains controversial. While chemotherapy is often recommended for high-risk stage II disease, many low-grade tumors with similar histopathologic features will recur and ultimately cause cancer-associated mortality. The development of molecular markers that predict clinical outcome or response to therapy in stage II colon cancer is an important tool that could give clinicians added information in discussions regarding the role of adjuvant chemotherapy. While many potential molecular biomarkers have been investigated, to date none have been validated in prospective clinical trials. Among the most promising molecular markers to be studied are microsatellite instability and 18q and 17p loss of heterozygosity, both of which are currently being evaluated as prognostic indicators in a large prospective clinical trial (Eastern Cooperative Oncology Group 5202). This review focuses on potential molecular biomarkers being evaluated for their prognostic value in stage II colon cancer and their potential role in clinical decision-making regarding the use of adjuvant chemotherapy.

UNG-initiated base excision repair is the major repair route for 5-fluorouracil in DNA, but 5-fluorouracil cytotoxicity depends mainly on RNA incorporation

Cytotoxicity of 5-fluorouracil (FU) and 5-fluoro-2′-deoxyuridine (FdUrd) due to DNA fragmentation during DNA repair has been proposed as an alternative to effects from thymidylate synthase (TS) inhibition or RNA incorporation. The goal of the present study was to investigate the relative contribution of the proposed mechanisms for cytotoxicity of 5-fluoropyrimidines. We demonstrate that in human cancer cells, base excision repair (BER) initiated by the uracil–DNA glycosylase UNG is the major route for FU–DNA repair in vitro and in vivo. SMUG1, TDG and MBD4 contributed modestly in vitro and not detectably in vivo. Contribution from mismatch repair was limited to FU:G contexts at best. Surprisingly, knockdown of individual uracil–DNA glycosylases or MSH2 did not affect sensitivity to FU or FdUrd. Inhibitors of common steps of BER or DNA damage signalling affected sensitivity to FdUrd and HmdUrd, but not to FU. In support of predominantly RNA-mediated cytotoxicity, FU-treated cells accumulated ~3000- to 15 000-fold more FU in RNA than in DNA. Moreover, FU-cytotoxicity was partially reversed by ribonucleosides, but not deoxyribonucleosides and FU displayed modest TS-inhibition compared to FdUrd. In conclusion, UNG-initiated BER is the major route for FU–DNA repair, but cytotoxicity of FU is predominantly RNA-mediated, while DNA-mediated effects are limited to FdUrd.

Review of histopathological and molecular prognostic features in colorectal cancer

Prediction of prognosis in colorectal cancer is vital for the choice of therapeutic options. Histopathological factors remain paramount in this respect. Factors such as tumor size, histological type and subtype, presence of signet ring morphology and the degree of differentiation as well as the presence of lymphovascular invasion and lymph node involvement are well known factors that influence outcome. Our understanding of these factors has improved in the past few years with factors such as tumor budding, lymphocytic infiltration being recognized as important. Likewise the prognostic significance of resection margins, particularly circumferential margins has been appreciated in the last two decades. A number of molecular and genetic markers such as KRAS, BRAF and microsatellite instability are also important and correlate with histological features in some patients. This review summarizes our current understanding of the main histopathological factors that affect prognosis of colorectal cancer.

Microsatellite instability in the management of colorectal cancer

Microsatellite instability (MSI) is a form of genetic instability caused by alterations in the DNA mismatch repair system. Approximately 15% of colorectal cancers display MSI due to a germline mutation in one of the mismatch repair genes (MLH1, MSH2, MSH6 and PMS2) or to epigenetic silencing of MLH1. Colorectal cancers with MSI have distinctive features, including a tendency to arise in the proximal colon, poor differentiation, lymphocytic infiltration and mucinous or signet-ring histology. Patients with MSI tumors appear to have a better prognosis than those with microsatellite stable tumors, but curiously the responses to 5-fluorouracil-based chemotherapy regimens are poorer with MSI tumors. Preliminary data suggest possible advantages of irinotecan-based regimens, but these findings need validation in well-designed clinical trials.

DNA mismatch repair status and colon cancer recurrence and survival in clinical trials of 5-fluorouracil-based adjuvant therapy

BACKGROUND

Approximately 15% of colorectal cancers develop because of defective function of the DNA mismatch repair (MMR) system. We determined the association of MMR status with colon cancer recurrence and examined the impact of 5-fluorouracil (FU)-based adjuvant therapy on recurrence variables.

METHODS

We included stage II and III colon carcinoma patients (n = 2141) who were treated in randomized trials of 5-FU-based adjuvant therapy. Tumors were analyzed for microsatellite instability by polymerase chain reaction and/or for MMR protein expression by immunohistochemistry to determine deficient MMR (dMMR) or proficient MMR (pMMR) status. Associations of MMR status and/or 5-FU-based treatment with clinicopathologic and recurrence covariates were determined using χ(2) or Fisher Exact or Wilcoxon rank-sum tests. Time to recurrence (TTR), disease-free survival (DFS), and overall survival (OS) were analyzed using univariate and multivariable Cox models, with the latter adjusted for covariates. Tumors showing dMMR were categorized by presumed germline vs sporadic origin and were assessed for their prognostic and predictive impact. All statistical tests were two-sided.

RESULTS

In this study population, dMMR was detected in 344 of 2141 (16.1%) tumors. Compared with pMMR tumors, dMMR was associated with reduced 5-year recurrence rates (33% vs 22%; P < .001), delayed TTR (P < .001), and fewer distant recurrences (22% vs 12%; P < .001). In multivariable models, dMMR was independently associated with delayed TTR (hazard ratio = 0.72, 95% confidence interval = 0.56 to 0.91, P = .005) and improved DFS (P = .035) and OS (P = .031). In stage III cancers, 5-FU-based treatment vs surgery alone or no 5-FU was associated with reduced distant recurrence for dMMR tumors (11% vs 29%; P = .011) and reduced recurrence to all sites for pMMR tumors (P < .001). The dMMR tumors with suspected germline mutations were associated with improved DFS after 5-FU-based treatment compared with sporadic tumors where no benefit was observed (P = .006).

CONCLUSIONS

Patients with dMMR colon cancers have reduced rates of tumor recurrence, delayed TTR, and improved survival rates, compared with pMMR colon cancers. Distant recurrences were reduced by 5-FU-based adjuvant treatment in dMMR stage III tumors, and a subset analysis suggested that any treatment benefit was restricted to suspected germline vs sporadic tumors.

DNA mismatch repair status and colon cancer recurrence and survival in clinical trials of 5-fluorouracil-based adjuvant therapy

BACKGROUND

Approximately 15% of colorectal cancers develop because of defective function of the DNA mismatch repair (MMR) system. We determined the association of MMR status with colon cancer recurrence and examined the impact of 5-fluorouracil (FU)-based adjuvant therapy on recurrence variables.

METHODS

We included stage II and III colon carcinoma patients (n = 2141) who were treated in randomized trials of 5-FU-based adjuvant therapy. Tumors were analyzed for microsatellite instability by polymerase chain reaction and/or for MMR protein expression by immunohistochemistry to determine deficient MMR (dMMR) or proficient MMR (pMMR) status. Associations of MMR status and/or 5-FU-based treatment with clinicopathologic and recurrence covariates were determined using χ(2) or Fisher Exact or Wilcoxon rank-sum tests. Time to recurrence (TTR), disease-free survival (DFS), and overall survival (OS) were analyzed using univariate and multivariable Cox models, with the latter adjusted for covariates. Tumors showing dMMR were categorized by presumed germline vs sporadic origin and were assessed for their prognostic and predictive impact. All statistical tests were two-sided.

RESULTS

In this study population, dMMR was detected in 344 of 2141 (16.1%) tumors. Compared with pMMR tumors, dMMR was associated with reduced 5-year recurrence rates (33% vs 22%; P < .001), delayed TTR (P < .001), and fewer distant recurrences (22% vs 12%; P < .001). In multivariable models, dMMR was independently associated with delayed TTR (hazard ratio = 0.72, 95% confidence interval = 0.56 to 0.91, P = .005) and improved DFS (P = .035) and OS (P = .031). In stage III cancers, 5-FU-based treatment vs surgery alone or no 5-FU was associated with reduced distant recurrence for dMMR tumors (11% vs 29%; P = .011) and reduced recurrence to all sites for pMMR tumors (P < .001). The dMMR tumors with suspected germline mutations were associated with improved DFS after 5-FU-based treatment compared with sporadic tumors where no benefit was observed (P = .006).

CONCLUSIONS

Patients with dMMR colon cancers have reduced rates of tumor recurrence, delayed TTR, and improved survival rates, compared with pMMR colon cancers. Distant recurrences were reduced by 5-FU-based adjuvant treatment in dMMR stage III tumors, and a subset analysis suggested that any treatment benefit was restricted to suspected germline vs sporadic tumors.

Genetic-based biomarkers and next-generation sequencing: the future of personalized care in colorectal cancer

The past 5 years have witnessed extraordinary advances in the field of DNA sequencing technology. What once took years to accomplish with Sanger sequencing can now be accomplished in a matter of days with next-generation sequencing (NGS) technology. This has allowed researchers to sequence individual genomes and match combinations of mutations with specific diseases. As cancer is inherently a disease of the genome, it is not surprising to see NGS technology already being applied to cancer research with promises of greater understanding of carcinogenesis. While the task of deciphering the cancer genomic code remains ongoing, we are already beginning to see the application of genetic-based testing in the area of colorectal cancer. In this article we will provide an overview of current colorectal cancer genetic-based biomarkers, namely mutations and other genetic alterations in cancer genome DNA, discuss recent advances in NGS technology and speculate on future directions for the application of NGS technology to colorectal cancer diagnosis and treatment.

Prognostic and predictive markers in stage II colon cancer: is there a role for gene expression profiling?

Conventional clinical and pathologic risk factors in stage II colon cancer provide limited prognostic information and do not predict response to adjuvant 5-fluorouracil-based chemotherapy. New prognostic and predictive biomarkers are needed to identify patients with highest recurrence risk who will receive the greatest absolute risk reduction from adjuvant chemotherapy. We review below the evidence for conventional risk factors in patients with node-negative colon cancer, followed by a discussion of promising new molecular and genetic markers in this malignancy. Gene expression profiling is an emerging tool with both prognostic and predictive potential in oncology. For patients with stage II colon cancer, the Oncotype DX Colon Cancer test is now commercially available as a prognostic marker, and the ColoPrint assay is expected to be released later this year. Current evidence for both of these assays is described below, concluding with a discussion of potential future directions for gene expression profiling in colon cancer risk stratification and treatment decision making.

Microsatellite instability in colorectal cancer: from molecular oncogenic mechanisms to clinical implications

BACKGROUND

Microsatellite instability (MSI) constitutes an important oncogenic molecular pathway in colorectal cancer (CRC), representing approximately 15% of all colorectal malignant tumours. In roughly one third of the cases, the underlying DNA mismatch repair (MMR) defect is inherited through the transmission of a mutation in one of the genes involved in MMR, predominantly MSH2 and MLH1, or less frequently, MSH6 or PMS2. In the overwhelming number of sporadic cases, MSI results from epigenetic MLH1 silencing through hypermethylation of its promoter. MMR deficiency promotes colorectal oncogenesis through the accumulation of numerous mutations in crucial target genes harbouring mononucleotide repeats, notably in those involved in the control of cell proliferation and differentiation, as well as DNA damage signalling and repair.

DESIGN

In this review, we describe the molecular aspects of the MMR system and the biological consequences of its defect on the oncogenic process, and we discuss the various experimental systems used to evaluate the efficacy of cytotoxic drugs on MSI colorectal cells lines. There is increasing evidence showing that MSI CRCs differ from all CRCs in terms of prognosis and response to the treatment. We report the clinical studies that have evaluated the prognostic and predictive value of MSI status on clinical outcome in patients treated with various chemotherapy regimens used in the adjuvant setting or for advanced CRCs.

CONCLUSION

In view of this, the opportunity of a systematic MSI phenotyping in the clinical management of patients with CRC is further discussed.

Predictive and prognostic factors in colorectal cancer: a personalized approach

It is an exciting time for all those engaged in the treatment of colorectal cancer. The advent of new therapies presents the opportunity for a personalized approach to the patient. This approach considers the complex genetic mechanisms involved in tumorigenesis in addition to classical clinicopathological staging. The potential predictive and prognostic biomarkers which have stemmed from the study of the genetic basis of colorectal cancer and therapeutics are discussed with a focus on mismatch repair status, KRAS, BRAF, 18qLOH, CIMP and TGF-β.

XELOX in colorectal cancer: a convenient option for the future?

XELOX is a 3-weekly chemotherapy combination of oral capecitabine and intravenous oxaliplatin. The central hypothesis that led to its development was that it would provide a convenient and cost-effective alternative to intravenous fluorouracil-based chemotherapy doublets, without compromising on anti-tumor efficacy. Recently its role in colorectal cancer has become more established in both the metastatic and adjuvant setting. Ongoing investigation of XELOX continues in a number of directions: its combination with novel biological agents, its efficacy and safety in the elderly, and the development of biomarkers that can predict its anti-tumor effect. This article provides a comprehensive and up-to-date synopsis of all pertinent clinical studies detailing this regimen and its promise for the future.

Personalized medicine and oncology practice guidelines: a case study of contemporary biomarkers in colorectal cancer

Predictive and prognostic biomarkers offer a potential means to personalize cancer medicine, although many reach the market-place before they have been validated, and their adoption is often hindered by variable clinical evidence. Because of this variability in supporting evidence, clinical practice guidelines formulated by panels of subspecialty experts may be particularly important in guiding stakeholders' acceptance and use of new personalized medicine biomarker tests and other nascent technologies. This article provides a structured review of the clinical evidence supporting 4 contemporary biomarker tests in colorectal cancer: K-ras and B-raf mutation analyses, mismatch repair protein testing, and the Oncotype DX Colon Cancer Assay. All 4 tests have been evaluated for guideline inclusion by the NCCN Guidelines Panel for Colon Cancer. This case study shows significant variability in the level of clinical evidence associated with these tests. In the cases of B-raf and mismatch repair protein testing, the available evidence is also inconsistent as it pertains to the specific NCCN Guideline recommendation. Based on this uncertainty in the evidence base, the authors conclude that expert clinical judgment, experience, and consensus may be more heavily weighted than published clinical trial data in the evaluation of new personalized medicine biomarker tests. Potential implications of this conclusion and future directions for research are discussed.

Analysis of the immunohistochemical expressions of p53, bcl-2 and Ki-67 in colorectal adenocarcinoma and their correlations with the prognostic factors

CONTEXT

Search of tumors markers that allow treatment with higher survival rates, and indicate the response to treatment and recurrence of cancer

OBJECTIVE

To analyze the immunoexpression of the proteins p53, bcl-2 and Ki-67 in colorectal adenocarcinoma and correlate them with the clinical-pathological prognostic factors.

METHOD

Tissue microarray paraffin blocks were made from colorectal adenocarcinoma tissue resected from 82 patients who had undergone surgery but not chemotherapy or radiotherapy, at "Hospital São Paulo", São Paulo, SP, Brazil, between 2002 and 2005. Thin sections (4 microm) were subjected to immunohistochemical reactions, and immunoexpression staining scores were obtained. The scores were correlated with the degree of cell differentiation, staging, disease-free interval, recurrence, survival and specific mortality. The study variables were analyzed using the chi-square and Kaplan-Meier tests to investigate associations with the markers. The significance of the differences between the curves of the disease-free interval and survival was analyzed using the Logrank and Wilcoxon tests.

RESULTS

The immunohistochemical expression of p53 was positive in 70 tumors (85.4%) and negative in 12 (14.6%). The expression of bcl-2 was positive in 26 (31.7%) and negative in 56 (68.3%). The expression of Ki-67 was positive in 62 (75.6%) and negative in 20 (24.4%). There was no statistically significant correlation between the expressions of these markers separately or in conjunction, in relation to the degree of cell differentiation, staging, disease-free interval, survival and specific mortality. In relation to recurrence, there was a statistically significant correlation with positive expression of Ki-67 (P = 0.035).

CONCLUSION

The immunohistochemical expression of Ki-67 in colorectal cancer is associated with recurrence of this disease.

Tumour-infiltrating T-cell subsets, molecular changes in colorectal cancer, and prognosis: cohort study and literature review

The abundance of tumour-infiltrating T-cells has been associated with microsatellite instability (MSI) and a favourable prognosis in colorectal cancer. However, numerous molecular alterations have been associated with clinical outcome, and potentially confounding the biological and prognostic significance of tumour-infiltrating T-cells. We utilized a database of clinically and molecularly-annotated colon and rectal carcinoma cases (N = 768; stage I-IV) in two prospective cohort studies (the Nurses' Health Study and the Health Professionals Follow-up Study) and quantified the densities of CD3(+), CD8(+), CD45RO(+) (PTPRC), and FOXP3(+) cells within neoplastic epithelial areas using an Ariol image analysis system and tissue microarray. We used Cox proportional hazard models to compute the mortality hazard ratio, adjusting for clinical and molecular features including KRAS, BRAF, and PIK3CA mutations, MSI, CIMP, and LINE-1 hypomethylation. The densities of CD8(+), CD45RO(+), and FOXP3(+) cells were significantly associated with patient survival in univariate analyses (P(trend) < 0.007). In the multivariate model, tumour-infiltrating CD45RO(+)-cell density, but not CD3(+), CD8(+) or FOXP3(+)-cell density, was significantly associated with survival (p = 0.0032). In multivariate linear regression analysis, MSI-high (p < 0.0001) and high-level tumour LINE-1 methylation (p = 0.0013) were independently associated with higher CD45RO(+)-cell density. The survival benefit associated with CD45RO(+) cells was independent of MSI and LINE-1 status. In conclusion, tumour-infiltrating CD45RO(+)-cell density is a prognostic biomarker associated with longer survival of colorectal cancer patients, independent of clinical, pathological, and molecular features. In addition, MSI-high and tumour LINE-1 methylation level are independent predictors of CD45RO(+)-cell density. Our data offer a possible mechanism by which MSI confers an improved clinical outcome and support efforts to augment the host immune response in the tumour microenvironment as a strategy of targeted immunotherapy.

Improved testing for microsatellite instability in colorectal cancer using a simplified 3-marker assay

BACKGROUND

In colorectal cancer (CRC), microsatellite instability (MSI) is a valuable marker of defective DNA mismatch repair that identifies cancers with distinct phenotypic properties, including favorable survival. However, the optimal assay for MSI status is unknown. We have evaluated a simplified 3-marker assay for MSI and compared it with the 5-marker (NCI) assay to see if technical variations in MSI testing are important.

MATERIALS AND METHODS

DNA samples from 357 CRCs were evaluated for MSI using the 5 microsatellite markers recommended for the NCI assay (BAT 25, BAT26, D2S123, D5S346, and D17S250). Results were compared with a simplified 3-marker assay (BAT25, BAT26, and D2S123). CRCs identified as MSI were evaluated for their clinical, pathological, and genetic characteristics.

RESULTS

The 5-marker assay identified 96 cancers as MSI. Only 56 of these were MSI by the 3-marker assay (3-marker+ group), leaving 40 cases identified as MSI only by NCI criteria (3-marker- group). The remaining 261 cancers were microsatellite stable (MSS). The 3-marker+ MSI tumors had features characteristic of MSI tumors: more proximal, poorly differentiated, associated with hereditary nonpolyposis colorectal cancer (HNPCC), more BRAF mutations, fewer KRAS mutations, better 5-year disease-specific survival, more frequent mismatch repair (MMR) protein loss, and less likely to be metastatic on presentation (P < .05). Chromosomal arm loss was observed only in 3-marker- MSI and MSS cancers (P < .05).

CONCLUSION

The 3-marker MSI assay outperforms the traditional 5-marker assay for identifying patients with favorable prognosis and homogeneous clinical and genetic features. More accurate MSI testing should improve prognostic and predictive scoring systems for colorectal cancer.

Microsatellite instability in colorectal cancer

Approximately 20 percent of right-sided colon cancers and 5 percent of left-sided colon and rectal cancers have a deficient DNA mismatch repair system. This results in the widespread accumulation of mutations to nucleotide repeats, some of which occur within the coding regions of cancer-related genes such as TGFβRII and BAX. A standardized definition for microsatellite instability (MSI) based on the presence of deletions to mononucleotide repeats is gaining widespread acceptance in both research and the clinic. Colorectal cancer (CRC) with MSI are characterized histologically by an abundance of tumor-infiltrating lymphocytes, poor differentiation and a signet ring or mucinous phenotype. In younger patients these tumors usually develop along the chromosomal instability pathway, in which case the mismatch repair genes are inactivated by germline mutation, somatic mutation and loss of heterozygosity. In older patients MSI CRC usually develops against a background of widespread hypermethylation that includes methylation-induced silencing of the mismatch repair gene MLH1. The overall biological and clinical phenotype of MSI CRC that arise in these two pathways is likely to be different and may account for some of the discordant results reported in the literature relating to the clinical properties of these tumors. The available evidence indicates that MSI is unlikely to be a clinically useful marker for the prognostic stratification of early-stage CRC. The predictive value of MSI for response to 5-fluorouracil-based chemotherapy remains controversial, while for other agents the predictive value is difficult to assess because they are used in combination regimens. The MSI phenotype is being actively investigated for novel therapeutic approaches based on the principle of synthetic lethality. Finally, the MSI status of CRC is an extremely useful marker for population-based screening programs that aim to identify individuals and families with the hereditary cancer condition known as Lynch syndrome.

Clinical significance of microsatellite instability for stage II or III colorectal cancer following adjuvant therapy with doxifluridine

Microsatellite instability (MSI) is a molecular marker that can provide valuable prognostic information for colorectal cancer (CRC). However, the predictive role of the MSI status remains less clear than its role in prognostication due to mixed results from previous studies. Therefore, this study investigated the usefulness of the MSI status as a predictive factor for stage II or III CRC patients who received adjuvant doxifluridine therapy. Among 3030 patients with CRC who underwent surgical resection between 1997 and 2006, 564 patients were diagnosed with stage II or III, and adjuvant doxifluridine therapy was administered to 394 patients (70.0%). The MSI status was assessed using the markers BAT25 and BAT26, and samples with instability at both markers were scored as exhibiting high-frequency MSI (MSI-H). Among the 564 patients, 290 patients (51.4%) had stage II, and MSI-H was found in 41 patients (7.3%). With a median follow-up duration of 35.1 months (range, 0.5-135.2), the 5-year overall survival (OS) rate and relapse-free survival (RFS) rate were 87.5 and 76.2%, respectively. MSI-H showed a favorable survival trend for OS (P = 0.098) and significant survival benefit for RFS (P = 0.037) in all patients. In a univariate analysis, the doxifluridine-treated patients with MSI-H showed improved RFS compared to those with low or stable MSI (MSI-L/S) (P = 0.036), while the MSI status was not significantly associated with OS (P = 0.107). In a multivariate analysis, MSI-H was not significantly associated with RFS (Hazard ratio = 2.467, P = 0.125). In conclusion, this study confirmed the positive prognostic role of MSI-H. However, MSI-H patients with stage II or III CRC did not seem to benefit from doxifluridine adjuvant therapy.

Stage II and stage III colon cancer: treatment advances and future directions

Because of its frequency and mortality rate, colorectal cancer represents a major public health problem. Adjuvant chemotherapy has improved the prognosis. Six months of oxaliplatin and fluoropyrimidine in combination is the standard adjuvant treatment in stage III patients. Two monoclonal antibodies, bevacizumab targeting vascular endothelial growth factor and cetuximab targeting epidermal growth factor receptor 1, are being assessed in addition to chemotherapy in the adjuvant setting. Preliminary results of 2 trials have shown disappointing results. Duration of therapy is another other critical issue for the future. Adjuvant chemotherapy in patients with stage II colon cancer is still a subject of controversy. The potential biomarkers that can accurately select patients with stage II or III cancer who are at risk for recurrence to individualize therapy from microsatellite instability to gene signature are reviewed. Adjuvant therapy in elderly patients is another matter of debate due to the lack of survival advantage in the recent trials.

TTD consensus document on the diagnosis and management of hereditary colorectal cancer

Colorectal cancer is the first cause of cancer in occidental countries if we consider both male and females tumours. In Spain, 26,000 new cases are diagnosed every year. The possibilities of cure are higher if the tumour is diagnosed early. One of the most important risk factors for colorectal cancer is inheritance. Some hereditary syndromes, such as familial adenomatous polyposis (FAP), increase the risk by almost 100% and at a young age. Other more prevalent syndromes, such Lynch syndrome, increase the risk 10-12 times more than in the general population. This article aims at summarising the most important aspects in hereditary colorectal cancer and to be a useful tool to oncologists who work with these patients and their families.

Clinical, laboratory and molecular factors predicting chemotherapy efficacy and toxicity in colorectal cancer

Colorectal cancer (CRC) treatment has evolved significantly over the last ten years with the use of active chemotherapeutic agents including fluoropyrimidines, oxaliplatin and irinotecan plus targeted monoclonal antibodies bevacizumab, cetuximab and panitumumab. The addition of newer chemotherapeutic agents and targeted therapies has improved patient outcomes at the cost of increased toxicity with not all patients benefiting from these treatments. It is necessary for clinicians to more accurately predict clinical outcomes particularly in the predominantly elderly CRC patient population. This review aims to summarise existing data regarding the use of clinical and laboratory variables plus molecular markers in predicting response, survival and toxicity to chemotherapy agents and targeted monoclonal antibodies currently used in the treatment of CRC.

Mismatch repair protein expression is an independent prognostic factor in sporadic colorectal cancer

Abstract Background. Mismatch repair (MMR) status has been reported as a prognostic and predictive factor in sporadic colorectal cancer (CRC). The purpose of this study was to determine the prognostic and predictive value of MMR protein expression in the adjuvant setting. Patients and methods. The MMR status in the primary tumor was retrospectively assessed on paraffin-embedded formalin-fixed samples from 1 006 patients with sporadic CRC (488 stage II and 518 stage III) using immunohistochemical analysis (IHC) of MLH1 and MSH2 expression. The patients were included in adjuvant Nordic trials between 1991 and 1996 randomly assigned to surgery alone or surgery plus adjuvant 5-fluorouracil (5-FU)-based chemotherapy. Data was censored at 120 months after surgery. Results. One hundred fifty-seven patients (15.6%) showed a loss of MMR protein expression (139 MLH1 negative, 15 MSH2 negative and 3 MLH1 and MSH2 negative) and were classified as MMR protein negative. A normal MMR protein expression was found in 849 patients who were defined as MMR protein positive. MMR protein expression was a significant prognostic marker in the entire study group with a better overall survival (OS) among patients with MMR protein negative tumors compared to patients with MMR protein positive tumors (p=0.01). In a multivariate analysis the MMR protein expression was significantly associated with OS, (HR 0.70 [95% CI, 0.40 to 0.99]; p=0.01). The MMR status did not predict survival benefit from adjuvant 5-FU-based chemotherapy. Conclusion. This study reveals that IHC of MLH1 and MSH2 expression can yield important prognostic information but is not a predictive factor for adjuvant 5-FU-based chemotherapy in sporadic CRC.

DNA mismatch repair deficiency in sporadic colorectal cancer and Lynch syndrome

DNA mismatch repair (MMR) deficiency is one of the best understood forms of genetic instability in colorectal cancer (CRC), and is characterized by the loss of function of the MMR pathway. Failure to repair replication-associated errors due to a defective MMR system allows persistence of mismatch mutations all over the genome, but especially in regions of repetitive DNA known as microsatellites, giving rise to the phenomenon of microsatellite instability (MSI). A high frequency of instability at microsatellites (MSI-H) is the hallmark of the most common form of hereditary susceptibility to CRC, known as Lynch syndrome (LS) (previously known as hereditary non-polyposis colorectal cancer syndrome), but is also observed in approximately 15-20% of sporadic colonic cancers (and rarely in rectal cancers). Tumour analysis by both MMR protein immunohistochemistry and DNA testing for MSI is necessary to provide a comprehensive picture of molecular abnormality, for use in conjunction with family history data and other clinicopathological features, in order to distinguish LS from sporadic MMR-deficient CRC. Identification of the gene targets that become mutated in MMR-deficient tumours may explain, at least in part, some of the clinical, pathological and biological features of MSI-H CRCs and holds promise for developing novel therapeutics.

Defective mismatch repair as a predictive marker for lack of efficacy of fluorouracil-based adjuvant therapy in colon cancer

PURPOSE

Prior reports have indicated that patients with colon cancer who demonstrate high-level microsatellite instability (MSI-H) or defective DNA mismatch repair (dMMR) have improved survival and receive no benefit from fluorouracil (FU) -based adjuvant therapy compared with patients who have microsatellite-stable or proficient mismatch repair (pMMR) tumors. We examined MMR status as a predictor of adjuvant therapy benefit in patients with stages II and III colon cancer.

METHODS

MSI assay or immunohistochemistry for MMR proteins were performed on 457 patients who were previously randomly assigned to FU-based therapy (either FU + levamisole or FU + leucovorin; n = 229) versus no postsurgical treatment (n = 228). Data were subsequently pooled with data from a previous analysis. The primary end point was disease-free survival (DFS).

RESULTS

Overall, 70 (15%) of 457 patients exhibited dMMR. Adjuvant therapy significantly improved DFS (hazard ratio [HR], 0.67; 95% CI, 0.48 to 0.93; P = .02) in patients with pMMR tumors. Patients with dMMR tumors receiving FU had no improvement in DFS (HR, 1.10; 95% CI, 0.42 to 2.91; P = .85) compared with those randomly assigned to surgery alone. In the pooled data set of 1,027 patients (n = 165 with dMMR), these findings were maintained; in patients with stage II disease and with dMMR tumors, treatment was associated with reduced overall survival (HR, 2.95; 95% CI, 1.02 to 8.54; P = .04).

CONCLUSION

Patient stratification by MMR status may provide a more tailored approach to colon cancer adjuvant therapy. These data support MMR status assessment for patients being considered for FU therapy alone and consideration of MMR status in treatment decision making.

Combination therapy in high-risk stage II or stage III colon cancer: current practice and future prospects

Colon cancer represents the second leading cause of cancer-related deaths. For patients who have undergone curative surgery, adjuvant therapy can reduce the risk of recurrence and death from relapsed or metastatic disease. Postoperative chemotherapy with a 5-fluorouracil-based regimen combined with oxaliplatin is the current standard of care for stage III patients. However, there is still controversy in stage II disease about the real impact of adjuvant monotherapy or combined therapy on survival. Better identification of a subgroup of patients with a higher risk of recurrence can select patients who might benefit from adjuvant therapy. For the elderly population, there is a well-established role for postoperative therapy, although the most appropriate regimen remains to be defined. Targeted agents for combined adjuvant therapy in stage II and III colon cancer is a promising area, but to date, there is no evidence supporting its use in this setting. Results from large prospective trials with targeted therapy have been disappointing and new drugs and strategies are needed to define the role of these types of agents in the adjuvant scenario of colon cancer.

The loss of the CBX7 gene expression represents an adverse prognostic marker for survival of colon carcinoma patients

We have previously shown that CBX7 expression is associated with a more malignant phenotype in thyroid cancer. On this basis, we decided to investigate its possible prognostic value in colorectal cancer (CRC). CBX7 expression has been analysed by immunohistochemistry in tissue microarray (TMA) specimens obtained from a large series of sporadic CRC resections (n=1420). The CBX7 expression data have been correlated with several clinico-pathological parameters. CBX7 expression is reduced or absent in a significant number of CRC samples in comparison to the normal colonic mucosa and the loss of CBX7 expression correlates with a poor outcome of CRC (p<0.001). The block of CBX7 expression seems to occur at a transcriptional level since quantitative RT-PCR analysis showed a reduced CBX7-specific mRNA levels in CRC samples versus normal counterpart tissue (up to more than 50-fold). Finally, the restoration of CBX7 expression in two CRC cell lines reduces their proliferation rate suggesting a role of the loss of CBX7 expression in the progression step of colon carcinogenesis. Therefore, the data reported here indicate that the evaluation of CBX7 expression may represent a valid tool in the prognosis of colon cancer since a reduced survival of CRC patients is associated with the loss of CBX7 expression.

Microsatellite instability as a marker of prognosis and response to therapy: a meta-analysis of colorectal cancer survival data

BACKGROUND AND METHODS

We have reviewed and pooled data from published studies to evaluate the relationship between microsatellite instability (MSI) and colorectal cancer (CRC) prognosis. Thirty-one eligible studies reporting survival in 12782 patients characterised for MSI were pooled using a fixed- or random-effects model.

RESULTS

The summary odds ratio (OR) estimate for overall survival (OS) associated with MSI was 0.6 (95%CI 0.53-0.69, p<0.0001), with no evidence of heterogeneity. The effect was similar for disease-free survival (DFS) (OR=0.58, 95%CI 0.47-0.72, p<0.0001). In a subset of patients treated with 5-fluorouracil (5-FU)-based chemotherapy a significant improved prognosis was found for microsatellite stable (MSS) tumours (OR=0.52, 95%CI 0.4-0.6, p<0.0001) with no heterogeneity (p=0.53; I(2)=0%). By contrast a large heterogeneity characterised the data relative to 396 patients with MSI tumours (OR=0.69, 95%CI 0.3-1.5, p=0.1; heterogeneity: p=0.03; I(2)=58%).

CONCLUSIONS

This study confirmed the association between MSI and favourable prognosis as determined by both OS and DFS of CRC patients. A significant beneficial effect of 5-FU therapy was found for MSS tumours whilst no clear conclusion was reached for MSI tumours due to the high inter-study heterogeneity. We propose that this inconclusive result is due to the use of a single marker, such as MSI, that cannot account alone for the complexity of the mechanisms underlying 5-FU cytotoxicity. Future studies to predict response to 5-FU chemotherapy should include additional genome stability markers.

DNA mismatch repair and adjuvant chemotherapy in sporadic colon cancer

Defective DNA mismatch repair (MMR) occurs in approximately 15% of sporadic colorectal cancers (CRCs). Multiple retrospective studies have shown that patients with MMR-deficient CRCs have a more favorable stage-adjusted prognosis compared with those who have MMR-proficient tumors. Evidence also indicates that patients with MMR-deficient colon cancers do not benefit from treatment with adjuvant 5-fluorouracil chemotherapy. Furthermore, recent studies, including a pooled analysis, have validated the prognostic and predictive impact of MMR status in patients with stage II and III colon cancer who were treated in adjuvant chemotherapy trials. Given these data, it can be recommended that MMR status be determined and used to inform clinical decision-making for adjuvant chemotherapy in patients with stage II colon cancer.