Dose-Dense Temozolomide in Patients with MGMT-Silenced Chemorefractory Colorectal Cancer

MGMT function determines the differential response of ATR inhibitors with DNA-damaging agents in glioma stem cells for GBM therapy

Background

The most prevalent cancer treatments cause cell death through DNA damage. However, DNA damage response (DDR) repair pathways, initiated by tumor cells, can withstand the effects of anticancer drugs, providing justification for combining DDR inhibitors with DNA-damaging anticancer treatments.

Methods

Cell viability assays were performed with CellTiter-Glo assay. DNA damage was evaluated using Western blotting analysis. RNA-seq and single-cell level expression were used to identify the DDR signatures. In vivo, studies were conducted in mice to determine the effect of ATris on TMZ sensitization.

Results

We found a subpopulation of glioma sphere-forming cells (GSCs) with substantial synergism with temozolomide (TMZ) using a panel of 3 clinical-grade ataxia-telangiectasia- and Rad3-related kinase inhibitors (ATRis), (elimusertib, berzosertib, and ceralasertib). Interestingly, most synergistic cell lines had O6-methylguanine-DNA methyltransferase (MGMT) promoter methylation, indicating that ATRi mainly benefits tumors with no MGMT repair. Further, TMZ activated the ATR-checkpoint kinase 1 (Chk1) axis in an MGMT-dependent way. TMZ caused ATR-dependent Chk1 phosphorylation and DNA double-strand breaks as shown by increased γH2AX. Increased DNA damage and decreased Chk1 phosphorylation were observed upon the addition of ATRis to TMZ in MGMT-methylated (MGMT-) GSCs. TMZ also improved sensitivity to ATRis in vivo, as shown by increased mouse survival with the TMZ and ATRi combination treatment.

Conclusions

This research provides a rationale for selectively targeting MGMT-methylated cells using ATRis and TMZ combination. Overall, we believe that MGMT methylation status in GBM could serve as a robust biomarker for patient selection for ATRi combined with TMZ.

Improved Pathologic response to chemoradiation in MGMT methylated locally advanced rectal cancer

BACKGROUND AND PURPOSE

With the growing interest in total neoadjuvant treatment for locally advanced rectal adenocarcinoma (LARC) there is an urgent unmet need to identify predictive markers of response to long-course neoadjuvant concurrent chemoradiotherapy (LCRT). O6-Methylguanine (O6-MG)-DNA-methyltransferase (MGMT) gene methylation has been associated in some malignancies with response to concurrent chemoradiotherapy. We attempted to find if pathologic response to LCRT was associated with MGMT promoter hypermethylation (MGMTh).

MATERIALS AND METHODS

Patients were identified with LARC, available pre-treatment biopsy specimens, and at least 1 year of follow-up who received LCRT followed by surgical resection within 6 months. Biopsies were tested for MGMTh using a Qiagen pyrosequencing kit (Catalog number 970061). The primary outcome of LCRT responsiveness was based on tumor regression grade (TRG), with grades of 0-1 considered to have excellent response and grades of 2-3 considered to be non-responders. Secondary outcomes included overall survival (OS) and recurrence free survival (RFS).

RESULTS

Of 96 patients who met inclusion criteria, 76 had samples which produced reliable assay results. MGMTh corresponded with higher grade and age of the biopsy specimen. The percentage of responders to LCRT was higher amongst the MGMTh patients than the MGMTn patients (60.0% vs 27.5%, p value = 0.0061). MGMTh was not significantly associated with improved OS (2-year OS of 96.0% vs 98.0%, p = 0.8102) but there was a trend for improved RFS (2-year RFS of 87.6% vs 74.2%, p = 0.0903).

CONCLUSION

Significantly greater tumor regression following LCRT was seen in MGMTh LARC. Methylation status may help identify good candidates for close observation without surgery following LCRT.

Temozolomide Followed by Combination With Low-Dose Ipilimumab and Nivolumab in Patients With Microsatellite-Stable, O6-Methylguanine-DNA Methyltransferase-Silenced Metastatic Colorectal Cancer: The MAYA Trial

This is a multicenter, single-arm phase II trial evaluating the efficacy and safety of an immune-sensitizing strategy with temozolomide priming followed by a combination of low-dose ipilimumab and nivolumab in patients with microsatellite-stable (MSS) and O⁶-methylguanine–DNA methyltransferase (MGMT)–silenced metastatic colorectal cancer (mCRC).

MAYA shows that temozolomide priming followed by Ipi/Nivo combo induces durable benefit in MSS/MGMT-silenced mCRC.

Immune Checkpoint Inhibitors in Mismatch Repair Proficient/Microsatellite Stable Metastatic Colorectal Cancer Patients: Insights from the AtezoTRIBE and MAYA Trials

Simple Summary

Immune-checkpoint inhibitors (ICI) show modest activity and efficacy in microsatellite stable (MSS) metastatic colorectal cancer (mCRC) patients harbouring a proficient mismatch repair system (pMMR). Recently, two phase 2 trials -AtezoTRIBE and MAYA- have challenged this dogma through the administration of an intense first-line chemotherapy backbone consisting of FOLFOXIRI/bevacizumab in patients unselected for their microsatellite status, and immune priming with temozolomide in chemorefractory pMMR/MSS patients with silencing of O6-methylguanine-DNA methyltransferase (MGMT), respectively, reporting promising results. We here present the founding biological rationale of these two studies and their main findings. At the same time, we stress their strengths and drawbacks and open questions still to be address in future clinical investigations.

Abstract

In metastatic colorectal cancer (mCRC), remarkable advances have been achieved with immune checkpoint inhibitors (ICIs) targeting PD-1/PD-L1 and CTLA-4, only in a small subset of tumours (4–5%), harbouring a deficient mismatch repair system (dMMR)/microsatellite instability–high (MSI-H) or mutations in the catalytic subunit of polymerase epsilon (POLE). Within this framework, several combination strategies have been investigated to sensitize proficient mismatch repair (pMMR)/microsatellite stable (MSS) mCRC to ICIs, with disappointing results so far. However, at the last ESMO meeting, two phase II trials AtezoTRIBE and MAYA provided promising results in this field. In the comparative AtezoTRIBE trial, the addition of atezolizumab to FOLFOXIRI (5-fluoruracil, oxaliplatin and irinotecan) and bevacizumab led to a significant advantage in terms of progression free survival (PFS) in a population of untreated mCRC patients, not selected according to MMR/MSI status. In the single-arm MAYA trial, immune priming with temozolomide in pMMR/MSS chemo-resistant mCRC patients with silencing of O6-methylguanine-DNA methyltransferase (MGMT) allowed reporting signals of sensitivity to the subsequent therapy with nivolumab and a low dose of ipilimumab in some patients. Here, we discuss the rationale, results, criticisms and research perspectives opened by these two studies.

The Emergence of Immune-checkpoint Inhibitors in Colorectal Cancer Therapy

Immunotherapy has revolutionized the treatment landscape in a number of solid tumors. In colorectal cancer, evidence suggests that microsatellite high (MSI-H) tumors are the most responsive to immune checkpoint blockade due to increased neo-antigen load and a favorable tumor microenvironment. Indeed, Pembrolizumab now represents a first-line option in such patients. However, MSI-H tumors represent the minority and a proportion of patients' progress despite initially responding. Trials are investigating different immunotherapy combinatorial strategies to enhance immune response in less immunogenic colorectal tumors. Such strategies include dual immune checkpoint blockade, combining immune checkpoint inhibitors with other treatment modalities such as radiotherapy, chemotherapy or other biological or targeted agents. Moreover, there is an increasing drive to identify biomarkers to better select patients most likely to respond to immunotherapy and understand intrinsic and acquired resistance mechanisms. Apart from MSI-H tumors, there is a strong rationale to suggest that tumors with alterations in DNA polymerase epsilon and DNA polymerase delta are also likely to respond to immunotherapy and trials in this subpopulation are underway. Other strategies such as priming O6-methylguanineDNA methyltransferase silenced tumors with alkylating agents to make them receptive to immune checkpoint blockade are also being investigated. Here we discuss different colorectal subpopulations together with their likelihood of response to immune checkpoint blockade and strategies to overcome barriers to a successful clinical outcome. We summarize evidence from published clinical trials and provide an overview of trials in progress whilst discussing newer immunotherapy strategies such as adoptive cell therapies and cancer vaccines.

MGMT Immunohistochemical Expression in Colorectal Carcinoma and its Correlation with Tumor Progression

Introduction: There is an urgent need to identify predictive features and markers for colorectal carcinoma (CRC) progression and treatment. This study aimed to assess O6-methylguanine DNA methyltransferase (MGMT) expression in CRC and correlate with the clinico-pathological aspects of the tumor, also to evaluate the relationship between different histopathologic parameters and tumor progression. Material and Methods: The study was carried on 70 colectomy using formalin fixed paraffin embedded tumor tissue. Immunohistochemistry was used to detect MGMT expression, and clinico-pathologic aspects as well as Tumor budding, type of desmoplastic reaction, inflammatory lymphocytic milieu, pattern of invasive front and necrosis were assessed Then correlated with MGMT expression and tumor progression, using parametric and nonparametric statistical methods. Results: MGMT Loss of expression was detected in 42.9% of CRC cases. MGMT expression status was significantly correlated with tumor stage and metastatic status (p<0.05), while it was not correlated with other clinic-pathologic features, (p>0.05).  Desmoplastic reaction (DR), tumor budding, stromal tumor infiltrating lymphocytes (TIL-S) and necrosis were correlated with tumor stage (p<0.05). DR correlated with tumor budding (p<0.05). Both types of TIL and Crohn’s-like lymphoid reaction (CLR) showed a mutual correlation (p<0.05). Conclusion: MGMT high expression and histopathologic parameters as DR, tumor budding, inflammatory lymphocytic milieu and necrosis could be correlated with CRC progression.  

Temozolomide: An Updated Overview of Resistance Mechanisms, Nanotechnology Advances and Clinical Applications

Temozolomide (TMZ), an oral alkylating prodrug which delivers a methyl group to purine bases of DNA (O6-guanine; N7-guanine and N3-adenine), is frequently used together with radiotherapy as part of the first-line treatment of high-grade gliomas. The main advantages are its high oral bioavailability (almost 100% although the concentration found in the cerebrospinal fluid was approximately 20% of the plasma concentration of TMZ), its lipophilic properties, and small size that confer the ability to cross the blood-brain barrier. Furthermore, this agent has demonstrated activity not only in brain tumors but also in a variety of solid tumors. However, conventional therapy using surgery, radiation, and TMZ in glioblastoma results in a median patient survival of 14.6 months. Treatment failure has been associated with tumor drug resistance. This phenomenon has been linked to the expression of O6-methylguanine-DNA methyltransferase, but the mismatch repair system and the presence of cancer stem-like cells in tumors have also been related to TMZ resistance. The understanding of these mechanisms is essential for the development of new therapeutic strategies in the clinical use of TMZ, including the use of nanomaterial delivery systems and the association with other chemotherapy agents. The aim of this review is to summarize the resistance mechanisms of TMZ and the current advances to improve its clinical use.

Temozolomide modulates the expression of miRNAs in colorectal cancer

Cancer is the second leading cause of death globally, where nearly 1 in 6 deaths is due to cancer, with 70% of all deaths from cancer occur in low- and middle-income countries. The overall lifetime risk of developing colorectal cancer is 1 in 22 in men and 1 in 24 in women. In this work, we aimed to evaluate the role of temozolomide (TMZ) in controlling colon cancer cells (CRC) via regulating the miRnome. For this purpose, CRC cells (CaCo-2) were treated with 50 µM of TMZ for 48 h. Cell count using trypan test and cytotoxicity using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) were carried out, and the obtained results indicated a significant decrease in cell count (p = 0.029), and in the cell viability (p = 0.0019). Cell cycle analysis was performed using flow cytometer, and results showed that TMZ arrested CRC cells at G2/M phase. A total of 84 miRNAs were profiled using real time PCR, and the results indicated that TMZ treatment upregulated 15 of 84 miRNAs panel profiled and downregulated the rest. The TMZ-upregulated/downregulated miRNAs were predicted to interact with many epigenetic-related proteins i.e., DNMTs, EZH2, and SUV31H1. This study shed some light on the role of TMZ in regulating the miRnome of CRC and hence in different types of cancers.

Temozolomide and irinotecan (TEMIRI regimen) as salvage treatment of irinotecan-sensitive advanced colorectal cancer patients bearing MGMT methylation

Background

Non-randomized studies showed that temozolomide (TMZ) achieves an average 10% response rate in heavily pretreated metastatic colorectal cancer (mCRC) patients with promoter methylation of the DNA repair gene O6-methylguanine-DNA methyltransferase (MGMT). In this phase II trial, irinotecan and temozolomide (TEMIRI) combination regimen was assessed in irinotecan-sensitive, MGMT methylated/microsatellite stable (MSS) pretreated mCRC patients.

Patients and methods

Key inclusion criteria were centrally confirmed MGMT methylation by methylation-specific PCR, MSS mCRC, progression after at least two prior chemotherapy regimens for advanced disease and irinotecan-free interval >3 months. TEMIRI (TMZ 150 mg/m2 on days 1-5 plus irinotecan 100 mg/m2 on days 1, 15 q28 days) was administered for six cycles, followed by maintenance with TMZ. The primary end point was overall response rate (ORR). Exploratory translational analyses included MGMT immunohistochemistry (IHC) and methyl-BEAMing (MB).

Results

Between December 2014 and June 2017, 25 patients were enrolled. The primary end point was met, since six patients achieved a partial response [ORR 24%, 95% confidence interval (CI) 11% to 43%]. At a median follow-up of 15.6 months, median progression-free survival (mPFS) and overall survival (mOS) were 4.4 and 13.8 months, respectively. Only four (16%) patients had ≥ grade 3 (CTCAE 4.0) adverse events. All patients whose cancer was MGMT-positive IHC were non-responders. Consistently, patients with MGMT-negative/low tumors had a significantly longer mPFS than others (6.9 versus 2.0 months; hazard ratio = 0.29, 95% CI 0.02-0.41; P = 0.003) and a non-significant trend for longer mOS. MB testing showed similar accuracy.

Conclusions

TEMIRI regimen is a safe and active option in pre-treated, irinotecan-sensitive mCRC patients with MGMT methylation.

Capecitabine and Temozolomide versus FOLFIRI in RAS-Mutated, MGMT-Methylated Metastatic Colorectal Cancer

PURPOSE

To determine whether second-line therapy with capecitabine and temozolomide was superior to irinotecan, leucovorin, and fluorouracil (FOLFIRI) in patients with RAS-mutated, methyl-guanine methyltransferase (MGMT)-methylated metastatic colorectal cancer (mCRC).

PATIENTS AND METHODS

In this randomized, phase II trial, we enrolled patients with RAS-mutated, MGMT-methylated mCRC after failure of oxaliplatin-based regimen. Patients with centrally confirmed MGMT methylation were stratified by first-line progression-free survival (PFS) and prior bevacizumab and randomized to either capecitabine plus temozolomide (arm A, CAPTEM) or FOLFIRI (arm B). The primary endpoint was PFS analyzed on intention-to-treat basis, with 90% power and one-sided significance level of 0.05 to detect an increase of median time from 2 months in arm B to 4 months in arm A.

RESULTS

Between November 2014 and May 2019, 86 patients were randomly assigned to arm A (n = 43) or arm B (n = 43). After a median follow-up of 30.5 months (interquartile range, 12.2-36.3), 79 disease progression or death events occurred. Superiority of arm A was not demonstrated (one-sided P = 0.223). Progression-free survival and overall survival were 3.5 (2.0-5.0) and 9.5 (8.2-25.8) in arm A versus 3.5 (2.3-6.1) and 10.6 (8.5-20.8) in arm B [HR = 1.19 (0.82-1.72) and HR = 0.97 (0.58-1.61)], respectively. Grade ≥3 treatment-related adverse events had higher incidence in arm B versus A (47.6% vs 16.3%), and quality of life was significantly worse in arm B. Patients with positive MGMT expression by IHC did not benefit from CAPTEM.

CONCLUSIONS

Temozolomide-based therapy warrants further investigation in molecularly hyperselected subgroups.

Temozolomide Sensitizes MGMT-Deficient Tumor Cells to ATR Inhibitors

O⁶-methylguanine-DNA methyltransferase (MGMT) is an enzyme that removes alkyl groups at the O⁶-position of guanine in DNA. MGMT expression is reduced or absent in many tumor types derived from a diverse range of tissues, most notably in glioma. Low MGMT expression confers significant sensitivity to DNA alkylating agents such as temozolomide, providing a natural therapeutic index over normal tissue. In this study, we sought to identify novel approaches that could maximally exploit the therapeutic index between tumor cells and normal tissues based on MGMT expression, as a means to enhance selective tumor cell killing. Temozolomide, unlike other alkylators, activated the ataxia telangiectasia and Rad3-related (ATR)-checkpoint kinase 1 (Chk1) axis in a manner that was highly dependent on MGMT status. Temozolomide induced growth delay, DNA double-strand breaks, and G₂-M cell-cycle arrest, which led to ATR-dependent phosphorylation of Chk1; this effect was dependent on reduced MGMT expression. Treatment of MGMT-deficient cells with temozolomide increased sensitivity to ATR inhibitors both in vitro and in vivo across numerous tumor cell types. Taken together, this study reveals a novel approach for selectively targeting MGMT-deficient cells with ATR inhibitors and temozolomide. As ATR inhibitors are currently being tested in clinical trials, and temozolomide is a commonly used chemotherapeutic, this approach is clinically actionable. Furthermore, this interaction potently exploits a DNA-repair defect found in many cancers. SIGNIFICANCE: Monofunctional alkylating agents sensitize MGMT-deficient tumor cells to ATR inhibitors.

Constitutional mismatch repair-deficiency: current problems and emerging therapeutic strategies

Mismatch repair (MMR) proteins remove errors from newly synthesized DNA, improving the fidelity of DNA replication. A loss of MMR causes a mutated phenotype leading to a predisposition to cancer. In the last 20 years, an increasing number of patients have been described with biallelic MMR gene mutations in which MMR defects are inherited from both parents. This leads to a syndrome with recessive inheritance, referred to as constitutional mismatch repair-deficiency (CMMRD). CMMRD is a rare childhood cancer predisposition syndrome. The spectrum of CMMRD tumours is broad and CMMRD-patients possess a high risk of multiple cancers including hematological, brain and intestinal tumors. The severity of CMMRD is highlighted by the fact that patients do not survive until later life, emphasising the requirement for new therapeutic interventions. Many tumors in CMMRD-patients are hypermutated leading to the production of truncated protein products termed neoantigens. Neoantigens are recognized as foreign by the immune system and induce antitumor immune responses. There is growing evidence to support the clinical efficacy of neoantigen based vaccines and immune checkpoint inhibitors (collectively referred to as immunotherapy) for the treatment of CMMRD cancers. In this review, we discuss the current knowledge of CMMRD, the advances in its diagnosis, and the emerging therapeutic strategies for CMMRD-cancers.

Trifluridine/Tipiracil (TAS-102) in Refractory Metastatic Colorectal Cancer: A Multicenter Register in the Frame of the Italian Compassionate Use Program

BACKGROUND

TAS-102 is indicated for patients with metastatic colorectal cancer (mCRC) previously treated with, or not considered candidates for, available therapies. Given the complete inefficacy in half of patients, the lack of predictive factors, the palliative setting, and the financial and clinical toxicity, optimizing the cost-benefit ratio is crucial. The "ColonLife" nomogram allows an estimate of the 12-week life expectancy of patients with refractory mCRC.

MATERIALS AND METHODS

We collected data from patients treated at eight Italian centers in the compassionate use program. Baseline characteristics of patients who were or were not progression free at 6 months were compared. The discriminative ability of the ColonLife nomogram was assessed. Among patients who received both TAS-102 and regorafenib, clinical outcomes of the two sequences were compared.

RESULTS

This study included 341 patients. Six (2%) and 93 (27%) patients achieved response and disease stabilization, respectively. The median progression-free survival (PFS) was 2.4 months with an estimated 6-month PFS rate of 19%; the median overall survival (OS) was 6.2 months. An Eastern Cooperative Oncology Group performance status (ECOG PS) of 0, normal lactate dehydrogenase (LDH), and a time from the diagnosis of metastatic disease of >18 months were independently associated with higher chances of a patient being progression free at 6 months. The discriminative ability of ColonLife was confirmed. Among 121 patients who received both regorafenib and TAS-102, no differences in first or second PFS or OS were reported between the two sequences.

CONCLUSION

One out of five patients achieves clinical benefit with TAS-102. ECOG PS, LDH, and time from diagnosis of metastatic disease may help to identify these patients. Excluding patients with very short life expectancy appears a reasonable approach.

IMPLICATIONS FOR PRACTICE

Improving the cost-efficacy ratio of TAS-102 in metastatic colorectal cancer is needed to spare useless toxicities in a definitely palliative setting. Eastern Cooperative Oncology Group performance status, lactate dehydrogenase levels, and time from the diagnosis of metastatic disease may help to identify patients more likely to achieve benefit. Properly designed prognostic tools (i.e., the "ColonLife" nomogram) may enable excluding from further treatments patients with very limited life expectancy.

Clinical importance of DNA repair in sporadic colorectal cancer

Colorectal cancer (CRC) is the third major cause of cancer-related deaths worldwide. However, despite the scientific efforts to provide a molecular classification to improve CRC clinical practice management, prognosis and therapeutic decision are still strongly dependent on the TNM staging system. Mismatch repair system deficiencies can occur in many organs, but it is mainly a hallmark of CRC influencing clinical outcomes and response to therapy. This review will discuss the effect of the modulation of other DNA repair pathways (direct, excision and double strand break repairs) in the clinical and pathological aspects of colorectal cancer and its potential as prognostic and predictive biomarkers.

High microsatellite instability (MSI-H) colorectal carcinoma: a brief review of predictive biomarkers in the era of personalized medicine

Approximately 15 % of colorectal carcinomas (CRC) display high level microsatellite instability (MSI-H) due to either a germline mutation in one of the genes responsible for DNA mismatch repair (Lynch syndrome, 3 %) or somatic inactivation of the same pathway, most commonly through hypermethylation of the MLH1 gene (sporadic MSI-H, 12 %). Although heterogeneous, MSI-H colorectal carcinomas as a group show some distinct biologic characteristics when compared to CRC with stable or low level microsatellite instability. In the present review we will highlight therapeutically relevant characteristics of MSI-H tumors which could lead to specific responses to some conventional chemotherapy or novel targeted therapy agents.

A phase 2 study of temozolomide in pretreated metastatic colorectal cancer with MGMT promoter methylation

Background:

Presently, few options are available for refractory colorectal cancer (CRC). O6-methyl-guanine-DNA-methyltransferase (MGMT) promoter methylation is a frequent and early event in CRC tumourigenesis. This epigenetic silencing is a predictor of response to the alkylating drug temozolomide in glioblastoma. Preclinical evidences and some case reports showed temozolomide activity in CRC with MGMT silencing, but the available data from clinical trials are inconsistent.

Methods:

This was a multicentre, phase 2 trial, planned according to a two-stage Simon’s optimal design to investigate activity and safety of temozolomide in refractory CRC harbouring MGMT promoter methylation. The primary end point was overall response rate (ORR). Patients who failed two or more prior treatments received temozolomide at a dose of 150–200 mg m⁻² per day on days 1–5 every 28 days.

Results:

From July 2012 to June 2016, 225 patients were screened, 80 showed MGMT promoter methylation and 41 were enrolled. Overall response rate was 10% and disease control rate was 32%. Median progression-free survival and overall survival were 1.9 and 5.1 months, respectively.

Conclusions:

Temozolomide showed a modest activity in this heavily pretreated population and the study did not meet its primary end point. The role of temozolomide in CRC remains still controversial and further research is warranted.

Digital PCR assessment of MGMT promoter methylation coupled with reduced protein expression optimises prediction of response to alkylating agents in metastatic colorectal cancer patients

BACKGROUND

O(6)-methylguanine-DNA-methyltransferase (MGMT) is a repair protein, and its deficiency makes tumours more susceptible to the cytotoxic effect of alkylating agents. Five clinical trials with temozolomide or dacarbazine have been performed in metastatic colorectal cancer (mCRC) with selection based on methyl-specific PCR (MSP) testing with modest results. We hypothesised that mitigated results are consequences of unspecific patient selection and that alternative methodologies for MGMT testing such as immunohistochemistry (IHC) and digital polymerase chain reaction (PCR) could enhance patient enrolment.

PATIENTS AND METHODS

Formalin-fixed paraffin embedded archival tumour tissue samples from four phase II studies of temozolomide or dacarbazine in MGMT MSP-positive mCRCs were analysed by IHC for MGMT protein expression and by methyl-BEAMing (MB) for percentage of promoter methylation. Pooled data were then retrospectively analysed according to objective response rate, progression-free survival (PFS) and overall survival (OS).

RESULTS

One hundred and five patients were included in the study. Twelve had achieved partial response (PR) (11.4%), 24 stable disease (SD; 22.9%) and 69 progressive disease (PD; 65.7%). Patients with PR/SD had lower IHC scores and higher MB levels than those with PD. MGMT expression by IHC was negatively and MB levels positively associated with PFS (p < 0.001 and 0.004, respectively), but not with OS. By combining both assays, IHC low/MB high patients displayed an 87% reduction in the hazard of progression (p < 0.001) and a 77% in the hazard for death (p = 0.001).

CONCLUSION

In mCRC selected for MGMT deficiency by MSP, IHC and MB testing improve clinical outcome to alkylating agents. Their combination could enhance patient selection in this setting.

How the lab is changing our view of colorectal cancer

In metastatic colorectal cancer, the optimization of upfront treatment and the continuum of care based on patients' exposure to multiple treatment lines have reached a plateau of efficacy. Therefore, a paradigm shift is ongoing towards precision medicine and personalized treatments based on the specific molecular features of the disease. In this perspective, the improved knowledge of disease biology coming from the lab has prompted a rapid translation from bench to bedside of newer targeted strategies. Here, we focus on the most promising biomarkers already included or close to adoption in daily clinical practice. In particular, evidence about the potential roles of BRAF mutation, HER2 amplification, MGMT methylation, microsatellite instability, and ALK, ROS and NTRK1-3 rearrangements as positive predictors of benefit from biological agents is reviewed and discussed.