3D magnetic seed localization for augmented reality in surgery.

PURPOSE: For tumor resection, surgeons need to localize the tumor. For this purpose, a magnetic seed can be inserted into the tumor by a radiologist and, during surgery, a magnetic detection probe informs the distance to the seed for localization. In this case, the surgeon still needs to mentally reconstruct the position of the tumor from the probe's information. The purpose of this study is to develop and assess a method for 3D localization and visualization of the seed, facilitating the localization of the tumor. METHODS: We propose a method for 3D localization of the magnetic seed by extending the magnetic detection probe with a tracking-based localization. We attach a position sensor (QR-code or optical marker) to the probe in order to track its 3D pose (respectively, using a head-mounted display with a camera or optical tracker). Following an acquisition protocol, the 3D probe tip and seed position are subsequently obtained by solving a system of equations based on the distances and the 3D probe poses. RESULTS: The method was evaluated with an optical tracking system. An experimental setup using QR-code tracking (resp. using an optical marker) achieves an average of 1.6 mm (resp. 0.8 mm) 3D distance between the localized seed and the ground truth. Using a breast phantom setup, the average 3D distance is 4.7 mm with a QR-code and 2.1 mm with an optical marker. CONCLUSION: Tracking the magnetic detection probe allows 3D localization of a magnetic seed, which opens doors for augmented reality target visualization during surgery. Such an approach should enhance the perception of the localized region of interest during the intervention, especially for breast tumor resection where magnetic seeds can already be used in the protocol.

Copy number alterations and allelic ratio in relation to recurrence of rectal cancer.

BACKGROUND: In rectal cancer, total mesorectal excision surgery combined with preoperative (chemo)radiotherapy reduces local recurrence rates but does not improve overall patient survival, a result that may be due to the harmful side effects and/or co-morbidity of preoperative treatment. New biomarkers are needed to facilitate identification of rectal cancer patients at high risk for local recurrent disease. This would allow for preoperative (chemo)radiotherapy to be restricted to high-risk patients, thereby reducing overtreatment and allowing personalized treatment protocols. We analyzed genome-wide DNA copy number (CN) and allelic alterations in 112 tumors from preoperatively untreated rectal cancer patients. Sixty-six patients with local and/or distant recurrent disease were compared to matched controls without recurrence. Results were validated in a second cohort of tumors from 95 matched rectal cancer patients. Additionally, we performed a meta-analysis that included 42 studies reporting on CN alterations in colorectal cancer and compared results to our own data. RESULTS: The genomic profiles in our study were comparable to other rectal cancer studies. Results of the meta-analysis supported the hypothesis that colon cancer and rectal cancer may be distinct disease entities. In our discovery patient study cohort, allelic retention of chromosome 7 was significantly associated with local recurrent disease. Data from the validation cohort were supportive, albeit not statistically significant, of this finding. CONCLUSIONS: We showed that retention of heterozygosity on chromosome 7 may be associated with local recurrence in rectal cancer. Further research is warranted to elucidate the mechanisms and effect of retention of chromosome 7 on the development of local recurrent disease in rectal cancer.

Nuclear expression of histone deacetylases and their histone modifications predicts clinical outcome in colorectal cancer.

AIMS: Epigenetic changes are of crucial importance in cancer development and are potentially reversible; they are therefore targets of interest for anti-cancer therapy. The aim of this study was to investigate the clinical prognostic value of the histone deacetylases SIRT1, HDAC1 and HDAC2 and the histone modifications H4K16Ac and H3K56Ac in colorectal cancer. METHODS AND RESULTS: The epigenetic markers were immunohistochemically stained on tissue microarrays containing colorectal tumours (n = 254) and normal colorectal tissues (n = 50). Nuclear expression was assessed on the semi-automated Ariol system. Multivariate trend survival analyses of the combined markers showed better patient survival and less tumour recurrence when more markers showed high nuclear expression. For the combination of the histone deacetylases and H3K56Ac, the hazard ratio (HR) for overall survival (OS) was 0.82 [95% confidence interval (CI) 0.72-0.94; P = 0.005] and the HR for distant recurrence-free survival (DRFS) was 0.77 (95% CI 0.64-0.92; P = 0.003) per additional marker showing high expression. Similarly, for the combination of histone deactylases and H4K16Ac, HRs of 0.86 (95% CI 0.76-0.97; P = 0.01) for OS and 0.79 (95% CI 0.68-0.93; P = 0.006) for DRFS were observed per additional marker showing high expression. CONCLUSIONS: The studied epigenetic markers showed clinical prognostic value in colorectal cancer, both as individual markers and when combined into multimarker analyses. These results indicate that epigenetic mechanisms play an important role in colorectal carcinogenesis.

Age-dependent clinical prognostic value of histone modifications in colorectal cancer.

Aging is one of the prime risk factors for the development of cancer. Expression patterns of epigenetic regulators, including histone modification levels, are altered during aging of normal cells, a phenomenon referred to as epigenetic drift. Furthermore, it is known that epigenetic mechanisms are involved in the development of cancer. We hypothesized that expression of histone modifications, acetylation of histone 3 lysine 9 (H3K9Ac) and trimethylation of histone 3 lysine 27 (H3K27me3), with reported normal age-related expression patterns might show an age-dependent prognostic value in colorectal cancer (CRC). To quantify expression, we performed immunohistochemical staining of these histone modifications on a tissue microarray containing colorectal tissues of the 254 patients with TNM stage I-III CRC. Stratification of patients according to survival status revealed age-related tumor expression patterns of both H3K9Ac and H3K27me3. Decreased expression with advancing age was observed in patients who were alive after follow-up (no-event group), whereas increased expression with advancing age was observed in patients who presented with a recurrence or death in follow-up (event group). These opposite expression patterns translated into an age-dependent prognostic value in CRC for the individual histone modifications and their combination. The prognostic value reverses with advancing age, high nuclear expression associated with good clinical outcome in young adults, and, in contrast, with worse clinical outcome in elderly patients. In conclusion, for the first time, we demonstrated prognostic impact of epigenetic biomarkers that reverses with advancing age. This new insight supports the hypothesis that CRC biology is different in young vs elderly patients and emphasizes the importance of focusing on age-related effects in CRC.

Prognostic value of polycomb proteins EZH2, BMI1 and SUZ12 and histone modification H3K27me3 in colorectal cancer.

Numerous changes in epigenetic mechanisms have been described in various types of tumors. In search for new biomarkers, we investigated the expression of Polycomb-group (PcG) proteins EZH2, BMI1 and SUZ12 and associated histone modification H3K27me3 in colorectal cancer. Nuclear expression of PcG proteins and histone modification H3K27me3 were immunohistochemically (IHC) stained on a tissue microarray (TMA), including 247 tumor tissues and 47 normal tissues, and scored using the semi-automated Ariol system. Tumor tissues showed higher expression of EZH2 (p = 0.05) and H3K27me3 (p<0.001) as compared to their normal counterparts. Combined marker trend analyses indicated that an increase in the number of markers showing high expression was associated with better prognosis. High expression of all four markers in the combined marker analyses was correlated with the best patient survival and the longest recurrence-free survival, with overall survival (p = 0.01, HR 0.42(0.21-0.84)), disease-free survival (p = 0.007, HR 0.23(0.08-0.67) and local recurrence-free survival (p = 0.02, HR 0.30(0.11-0.84)). In conclusion, we found that expression of PcG proteins and H3K27me3 showed prognostic value in our study cohort. Better stratification of patients was obtained by combining the expression data of the investigated biomarkers as compared to the individual markers, underlining the importance of investigating multiple markers simultaneously.

DNA methylation of apoptosis genes in rectal cancer predicts patient survival and tumor recurrence.

Deregulation of the apoptotic pathway, one of the hallmarks of tumor growth and -progression, has been shown to have prognostic value for tumor recurrence in rectal cancer. In order to develop clinically relevant biomarkers, we studied the methylation status of promoter regions of key apoptosis genes in rectal cancer patients, using methylation-sensitive restriction enzymes. DNA was extracted from fresh-frozen tumor tissues of 49 stage I-III rectal cancer patients and 10 normal rectal tissues. The results of this pilot study were validated in 88 stage III tumor tissues and 18 normal rectal tissues. We found that methylation of the intrinsic apoptotic pathway genes Apaf1, Bcl2 and p53 correlated with the apoptotic status (M30) of the tumor. Combined survival analyses of these three genes, based on the number of genes showing high methylation (all low, 1 high, 2 high or all high), showed shorter patient survival and recurrence-free periods with an increasing number of methylated markers. Multivariate analyses showed significant differences for overall survival (p = 0.01; HR = 0.28 (0.09-0.83)), cancer-specific survival (p = 0.004; HR = 0.13 (0.03-0.67)) and distant recurrence-free survival (p = 0.001; HR = 0.22(0.05-0.94)). The shortest survival was observed for patients showing low methylation of all markers, which-as was expected-correlated with high apoptosis (M30), but also with high proliferation (Ki-67). The study of epigenetic regulation of apoptosis genes provides more insight in the tumorigenic process in rectal cancer and might be helpful in further refining treatment regimens for individual patients.

Histone trimethylation at H3K4, H3K9 and H4K20 correlates with patient survival and tumor recurrence in early-stage colon cancer.

BACKGROUND: Post-translational modification of histone tails by methylation plays an important role in tumorigenesis. In this study, we investigated the nuclear expression of H3K4me3, H3K9me3 and H4K20me3 in early-stage colon cancer in relation to clinical outcome. METHODS: Tumor tissue cores of 254 TNM stage I-III colorectal cancer patients were immunohistochemically stained for H3K4me3, H3K9me3 and H4K20me3 and scored using the semi-automated Ariol system. Cox proportional hazard trend analyses were performed to assess the prognostic value of the combined markers with respect to patient survival and tumor recurrence. RESULTS: The histone methylation markers only showed prognostic value in early-stage (TNM stage I and II) colon cancer. Therefore, only this patient set (n = 121) was used for further statistical analyses. Low nuclear expression of H3K4me3, and high expression of H3K9me3 and H4K20me3 were associated with good prognosis. In combined marker analyses, the patient group showing most favorable expression (low H3K4me3, high H3K9me3 and high H4K20me3) was associated with the best prognosis. Multivariate trend analyses showed significantly increased hazard ratios (HR) for each additional marker showing unfavorable expression, as compared to the "all favorable" reference group. The HR for disease-free survival was 3.81 (1.72-8.45; p = 0.001), for locoregional recurrence-free survival 2.86 (1.59-5.13; p < 0.001) and for distant recurrence-free survival 2.94 (1.66-5.22; p < 0.001). CONCLUSIONS: Combined nuclear expression of histone modifications H3K4me3, H3K9me3 and H4K20me3 is prognostic in early-stage colon cancer. The combination of expression of the three histone modifications provides better stratification of patient groups as compared to the individual markers and provides a good risk assessment for each patient group.

The homeobox gene MEIS1 is methylated in BRAF (p.V600E) mutated colon tumors.

Development of colorectal cancer (CRC) can occur both via gene mutations in tumor suppressor genes and oncogenes, as well as via epigenetic changes, including DNA methylation. Site-specific methylation in CRC regulates expression of tumor-associated genes. Right-sided colon tumors more frequently have BRAF (p.V600E) mutations and have higher methylation grades when compared to left-sided malignancies. The aim of this study was to identify DNA methylation changes associated with BRAF (p.V600E) mutation status. We performed methylation profiling of colon tumor DNA, isolated from frozen sections enriched for epithelial cells by macro-dissection, and from paired healthy tissue. Single gene analyses comparing BRAF (p.V600E) with BRAF wild type revealed MEIS1 as the most significant differentially methylated gene (log2 fold change: 0.89, false discovery rate-adjusted P-value 2.8*10(-9)). This finding was validated by methylation-specific PCR that was concordant with the microarray data. Additionally, validation in an independent cohort (n=228) showed a significant association between BRAF (p.V600E) and MEIS1 methylation (OR: 13.0, 95% CI: 5.2 - 33.0, P<0.0001). MEIS1 methylation was associated with decreased MEIS1 gene expression in both patient samples and CRC cell lines. The same was true for gene expression of a truncated form of MEIS1, MEIS1 D27 , which misses exon 8 and has a proposed tumor suppression function. To trace the origin of MEIS1 promoter methylation, 14 colorectal tumors were flow-sorted. Four out of eight BRAF (p.V600E) tumor epithelial fractions (50%) showed MEIS1 promoter methylation, as well as three out of eight BRAF (p.V600E) stromal fractions (38%). Only one out of six BRAF wild type showed MEIS1 promoter methylation in both the epithelial tumor and stromal fractions (17%). In conclusion, BRAF (p.V600E) colon tumors showed significant MEIS1 promoter methylation, which was associated with decreased MEIS1 gene expression.

The prognostic value of the apoptosis pathway in colorectal cancer: a review of the literature on biomarkers identified by immunohistochemistry.

Research towards biomarkers that predict patient outcome in colorectal cancer (CRC) is rapidly expanding. However, none of these biomarkers have been recommended by the American Association of Clinical Oncology or the European Group on Tumor Markers. Current staging criteria result in substantial under-and over-treatment of CRC patients. Evasion of apoptosis, a characteristic feature of tumorigenesis, is known to correlate with patient outcome. We reviewed the literature on immunohistochemistry-based studies between 1998 and 2011 describing biomarkers in this pathway in CRC and identified 26 markers. Most frequently described were p53, Bcl-2, survivin, and the Fas and TRAILR1 receptors and their ligands. None of the studies reviewed provided sufficient support for implementing a single marker into current clinical practice. This is likely due to the complex biology of this pathway. We suggest focusing on the combination of key markers within the apoptosis pathway that together represent an 'apoptotic tumor profile', which better reflects the status of this pathway in a tumor.

Independent validation of a prognostic genomic signature (ColoPrint) for patients with stage II colon cancer.

OBJECTIVES: The aim of this study was to independently validate a genomic signature developed both to assess recurrence risk in stage II patients and to assist in treatment decisions. BACKGROUND: Adjuvant therapy is recommended for high-risk patients with stage II colon cancer, but better tools to assess the patients' prognosis accurately are still required. METHODS: Previously, an 18-gene signature had been developed and validated on an independent cohort, using full genome microarrays. In this study, the gene signature was translated and validated as a robust diagnostic test (ColoPrint), using customized 8-pack arrays. In addition, clinical validation of the diagnostic ColoPrint assay was performed on 135 patients who underwent curative resection (R0) for colon cancer stage II in Munich. Fresh-frozen tissue, microsatellite instability status, clinical parameters, and follow-up data for all patients were available. The diagnostic ColoPrint readout was determined blindly from the clinical data. RESULTS: ColoPrint identified most stage II patients (73.3%) as at low risk. The 5-year distant-metastasis free survival was 94.9% for low-risk patients and 80.6% for high-risk patients. In multivariable analysis, ColoPrint was the only significant parameter to predict the development of distant metastasis with a hazard ratio of 4.28 (95% confidence interval, 1.36-13.50; P = 0.013). Clinical risk parameters from the American Society of Clinical Oncology (ASCO) recommendation did not add power to the ColoPrint classification. Technical validation of ColoPrint confirmed stability and reproducibility of the diagnostic platform. CONCLUSIONS: ColoPrint is able to predict the development of distant metastasis of patients with stage II colon cancer and facilitates the identification of patients who may be safely managed without chemotherapy.

Addition of interferon-α to the p53-SLP® vaccine results in increased production of interferon-γ in vaccinated colorectal cancer patients: a phase I/II clinical trial.

We previously established safety and immunogenicity of a p53 synthetic long peptides (p53-SLP®) vaccine. In the current trial, we investigated whether combination of interferon-alpha (IFN-α) with p53-SLP® is both safe and able to improve the induced p53-specific IFN-γ response. Eleven colorectal cancer patients successfully treated for metastatic disease were enrolled in this study. Of these, nine patients completed follow-up after two injections with p53-SLP® together with IFN-α. Safety and p53-specific immune responses were determined before and after vaccination. Furthermore, cryopreserved PBMCs were compared head-to-head to cryopreserved PBMCs obtained in our previous trial with p53-SLP® only. Toxicity of p53-SLP® vaccination in combination with IFN-α was limited to Grade 1 or 2, with predominantly small ongoing swellings at the vaccination site. All patients harbored p53-specific T cells after vaccination and most patients showed p53-specific antibodies. Compared to the previous trial, addition of IFN-α significantly improved the frequency of p53-specific T cells in IFN-γ ELISPOT. Moreover, in this trial, p53-specific T cells were detectable in blood samples of all patients in a direct ex vivo multiparameter flowcytometric assay, opposed to only 2 of 10 patients vaccinated with p53-SLP® only. Finally, patients in this trial displayed a broader p53-specific immunoglobulin-G response, indicating an overall better p53-specific T-helper response. Our study shows that p53-SLP® vaccination combined with IFN-α injection is safe and capable of inducing p53-specific immunity. When compared to a similar trial with p53-SLP® vaccination alone the combination was found to induce significantly more IFN-γ producing p53-specific T cells.

FoxP3- and CD8-positive Infiltrating Immune Cells Together Determine Clinical Outcome in Colorectal Cancer.

Immune cells are known to affect clinical outcome in colorectal cancer. Subsets of immune cells can both support and inhibit immunological interaction with tumor cells. We examined the clinical impact of T cells that are supposed to be responsible for the down regulation of a T cell response: regulatory T cells or Tregs. The study population (n = 76) consisted of a random population of colorectal cancer patients who did not receive any (neo-) adjuvant therapy, with a median follow-up time of 7.3 years (range 0.1-23.1 years). Expression of FoxP3 was used as an immunohistochemical marker to identify Tregs. We considered FoxP3+ cells present in tumor stroma and tumor epithelium separately, and related results to clinical outcome and to data on CD8+ immune cell infiltration that we previously obtained in the same patient cohort. All samples showed presence of Foxp3+ cells and in the majority of the patients (85.5%) these cells were also present in the tumor epithelial compartment. A relative high level of Foxp3+ cells in the tumor epithelium was significantly related to down regulation of HLA Class I expression (p-value 0.03). There was a trend, but no significant relation, towards a longer overall survival (p-value; 0.084) and disease-free survival (p-value; 0.073) when high levels of Foxp3+ cells were present in the tumor epithelium. More importantly, the ratio of CD8+/Foxp3+ cells did show a significant correlation with distant-recurrence-free survival. This was the case for both Foxp3+ cells specifically located in the tumor epithelium (p-value 0.024) as well as in the stroma compartment (p-value 0.018). Unfortunately due to the small sample size the ratios did not retain their statistical significance in multivariate analysis. These results provide further evidence that local interactions in the cancer microenvironment between tumor cells and immune cells are not only determined by tumor cell-related factors like HLA expression, but also by interactions among immune cells.

Biomarkers in precision therapy in colorectal cancer.

Colorectal cancer (CRC) is the most commonly diagnosed cancer in Europe. Because CRC is also a major cause of cancer-related deaths worldwide, a lot of research has been focused on the discovery and development of biomarkers to improve the diagnostic process and to predict treatment outcomes. Up till now only a few biomarkers are recommended by expert panels. Current TNM criteria, however, cause substantial under- and overtreatment of CRC patients. Consequently, there is a growing need for new and efficient biomarkers to ensure optimal treatment allocation. An ideal biomarker should be easily translated into clinical practice, to identify patients who can be spared from treatment or benefit from therapy, ultimately resulting in precision medicine in the future. In this review we aim to provide an overview of a number of frequently studied biomarkers in CRC and, at the same time, we will emphasize the challenges and controversies that withhold the clinical introduction of these biomarkers. We will discuss both prognostic and predictive markers of chemotherapy, aspirin therapy as well as overall therapy toxicity. Currently, only mutant KRAS, mutant BRAF, MSI and the Oncotype DX® Colon Cancer Assay are used in clinical practice. Other biomarker studies showed insufficient evidence to be introduced into clinical practice. Divergent patient selection criteria, absence of validation studies and a large number of single biomarker studies are possibly responsible. We therefore recommend that future studies focus on combining key markers, rather than analysing single markers, standardizing study protocols, and validate the results in independent study cohorts, followed by prospective clinical trials.

Prediction in rectal cancer.

The treatment of rectal cancer largely depends on disease stage at diagnosis, based on which patients can be classified as low, intermediate, or high risk. Prognostic and predictive markers, specific to each risk category, can be applied for optimal risk classification and subsequent treatment allocation. These markers are either histopathological, determined with imaging, or have a biomolecular background. This review provides an overview of the current status of treatment options and the use of prognostic and predictive markers in each risk category. An effort was made to identify those markers that are currently lacking in, but have the potential to improve, the clinical decision process by discussing the data from recent studies aimed at the development of new prognostic and predictive markers. At this moment, none of the markers studied has been proven to be of significant, independent value, justifying implementation in daily clinical practice. However, recent developments in imaging techniques and biomolecular research do show great potential.

Transanal endoscopic microsurgery for T1 rectal cancer: size matters!

BACKGROUND: Transanal endoscopic microsurgery (TEM) is considered a curative option for selected T1 rectal cancer. Although TEM is safe, local recurrence (LR) rates after TEM are unacceptably high. Evidence on selection criteria, however, is not abundant. To expand evidence on low- versus high-risk T1 rectal cancer with respect to LR, this study aimed to identify predictive histopathologic factors in a selected group of T1 rectal cancers treated with TEM only. METHODS: The study enrolled 62 patients for whom specimens of the primary tumor containing an invasive T1 carcinoma could be reevaluated. Tumors were scored according to predefined criteria, and analysis of predictive factors for locoregional failure was performed. RESULT: Local recurrence rates at 3 years for tumors 3 cm in size or smaller were significantly lower than for tumors larger than 3 cm (16 vs. 39%; P < 0.03). Combining smaller tumors with submucosal invasion depth and budding led to identifying tumors that likely will not recur (3-year LR rates, 7 and 10%, respectively). CONCLUSIONS: The findings showed that low- and high-risk criteria are too robust for identifying tumors at risk for LR. Tumor size alone or in combination with submucosal invasion depth or tumor budding appeared to be a significant predictive factor for locoregional failure after TEM for T1 rectal cancer.

PIK3CA kinase domain mutation identifies a subgroup of stage III colon cancer patients with poor prognosis.

BACKGROUND: PIK3CA mutations in the helical domain (in exon 9) and in the kinase domain (exon 20) cause tumor formation by different means. We aimed to determine the effects of each of these mutations on survival of colon carcinoma patients. METHODS: A large cohort of 685 colon carcinoma patients was tested for PIK3CA mutations in exons 9 and 20 by single nucleotide primer extension (N = 428) or by real time PCR (N = 257). RESULTS: PIK3CA mutation rate was 13%. 66 of 83 (79.5%) were in exon 9 and 17 of 83 (20.5%) in exon 20. In survival analysis, PIK3CA mutations in exon 9 and 20 had different effects on patient outcome. The PIK3CA exon 20 mutation conferred a poorer disease free survival compared to patients with wild type alleles and exon 9 mutations (Log rank p = 0.04 and p = 0.03 respectively) and cancer specific survival (Log rank p = 0.03 and p = 0.056 respectively) in stage III patients. In stage I and II this negative effect on outcome was not seen. CONCLUSIONS: PIK3CA mutation in exon 20 is a negative prognostic factor in stage III colon cancer patients. Moreover, this negative effect is not present in stage I and II patients.

Colorectal cancer vaccines in clinical trials.

This article elucidates current strategies of active immunotherapy for colorectal cancer patients with a focus on T-cell mediated immunotherapy. Poor prognosis of especially stage III and IV colorectal cancer patients emphasizes the need for advanced therapeutic intervention. Here, we refer to clinical trials using either tumor cell-derived vaccines or tumor antigen vaccines with a special interest on safety, induced immune responses, clinical benefit and efforts to improve the clinical impact of these vaccines in the context of colorectal cancer treatment.

PIK3CA mutations predict local recurrences in rectal cancer patients.

PURPOSE: Identifying rectal cancer patients at risk for local recurrence would allow for refinement in the selection of patients who would benefit from preoperative radiotherapy. PIK3CA, KRAS, and BRAF mutations are commonly found in colon cancers, but their prevalence has not been clearly assessed in rectal cancer. In this study, we aim to determine the mutation frequencies of PIK3CA, KRAS, and BRAF and to investigate whether a mutation may be used as a prognostic parameter in rectal cancer patients. EXPERIMENTAL DESIGN: We evaluated DNA mutations in PIK3CA, KRAS, and BRAF in 240 stage I to III rectal tumors obtained from nonirradiated patients from the Dutch Total Mesorectal Excision trial. RESULTS: PIK3CA, KRAS, and BRAF mutations were identified in 19 (7.9%), 81 (33.9%), and 5 (2.1%) rectal cancers. Patients with PIK3CA mutations developed more local recurrences (5-year risks, 27.8% versus 9.4%; P = 0.006) and tended to develop these recurrences more rapidly after surgery (median local recurrence-free interval since surgery: 7.9 versus 19.6 months; P = 0.07) than patients without PIK3CA mutations. In multivariate analysis, PIK3CA mutations remained as an independent predictor for the development of local recurrences (hazard ratio, 3.4; 95% confidence interval, 1.2-9.2; P = 0.017), next to tumor-node-metastasis stage. CONCLUSION: PIK3CA mutations can be used as a biomarker in identifying rectal cancer patients with an increased risk for local recurrences. Currently, our findings suggest that prospective evaluation of PIK3CA mutation status could reduce overtreatment by preoperative radiotherapy for the low-risk patients who might otherwise only experience the side effects.

Clinical impact of HLA class I expression in rectal cancer.

PURPOSE: To determine the clinical impact of human leukocyte antigen (HLA) class I expression in irradiated and non-irradiated rectal carcinomas. EXPERIMENTAL DESIGN: Tumor samples in tissue micro array format were collected from 1,135 patients. HLA class I expression was assessed after immunohistochemical staining with two antibodies (HCA2 and HC10). RESULTS: Tumors were split into two groups: (1) tumors with >50% of tumor cells expressing HLA class I (high) and (2) tumors with < or =50% of tumor cells expressing HLA class I (low). No difference in distribution or prognosis of HLA class I expression was found between irradiated and non-irradiated patients. Patients with low expression of HLA class I (15% of all patients) showed an independent significantly worse prognosis with regard to overall survival and disease-free survival. HLA class I expression had no effect on cancer-specific survival or recurrence-free survival. CONCLUSIONS: Down-regulation of HLA class I in rectal cancer is associated with poor prognosis. In contrast to our results, previous reports on HLA class I expression in colorectal cancer described a large population of patients with HLA class I negative tumors, having a good prognosis. This difference might be explained by the fact that a large proportion of HLA negative colon tumors are microsatellite instable (MSI). MSI tumors are associated with a better prognosis than microsatellite stable (MSS). As rectal tumors are mainly MSS, our results suggest that it is both, oncogenic pathway and HLA class I expression, that dictates patient's prognosis in colorectal cancer. Therefore, to prevent confounding in future prognostic analysis on the impact of HLA expression in colorectal tumors, separate analysis of MSI and MSS tumors should be performed.