Colorectal (February 2018): Molecular Oncology Tumor Boards

ASCO University
Feb 14, 2018 7:40 AM

Participant Instructions: Welcome to the Molecular Oncology Tumor Board Series! This educational initiative is a collaboration between the American Society of Clinical Oncology (ASCO), College of American Pathologists (CAP), and Association for Molecular Pathology (AMP).

A new case will be presented each month with discussions led by an expert pathologist and medical oncologist. This month’s topic is led by Drs. Peeters and Shi.

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Do you have an interesting case in mind? Submit your hypothetical patient cases for consideration in an upcoming Molecular Oncology Tumor Board discussion forum.

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Please see below for supplemental resources related to the case.



ASCO University
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 14, 2018 7:45 AM

Patient Case #1

Age/Sex: 46 years, female

Medical History: Appendectomy at age 19

Family History: An aunt had colon cancer at age 37

Type of Tumor: Semi-circular tumor located at the right colon

Relevant Markers:  CEA 5.3 µg/l (< 3.0 µg/l)

Prior Treatment History/Response: None

Co-morbidities: None

Images/Scans/Pathology: Biopsy of the colonic lesion: invasive, moderately differentiated adenocarcinoma. Image

Further staging did not reveal metastatic sites. Final clinical staging: cTxN0M0


ASCO University
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 14, 2018 7:50 AM

Discussion Questions

1.    The pathology report of the preoperative colonic biopsy concluded: moderately differentiated adenocarcinoma. As a treating physician, do we expect additional information in the pathology report?

2.    After right hemicolectomy, the final pathology report showed a pG2T3N1cM0 of the right colon. This woman has stage III colon cancer and based on the guidelines it is a clear indication for adjuvant therapy. Do we need more information on (molecular) pathology to decide on type of treatment?

3.    If we determine MSI-status in this case. Why is this important from a pathology perspective?


Anis Toumeh, MD
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 14, 2018 2:15 PM

I would be interested in knowing the lymphocytic infiltratoin status in the specimen 

The predictive role of MSI status in stage III disease, to my knowledge, is not conclusive. Hence, regardeless of her MSI status, I would recommend 5FU and Oxaliplatin based regimen 


Sachdev P. Thomas, MD
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 14, 2018 5:39 PM

I woudl also recommend 6 mos of adjuvant Oxal based chemo. COnsider referral to Genetics Clinic



ASCO University
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 19, 2018 8:41 AM

Course Faculty Response by Dr. Marc Peeters

Question 1: Yes as the treating physician, I do expect in this type of case, when you have a young patient with a family history (second degree) of colon cancer, it would place them at a higher risk category. Therefore, they should have a through work up to identify, whether the patient has a genetic predisposition.  Hence, the diagnosis of her colon cancer might be part of Lynch Syndrome, which will need to be ruled out.

Question 2: The importance on MSI status is related to the possible genetic background. It is less predictive for treatment decision. This is a stage III colon cancer and still today oxaliplatin-based chemotherapy is standard of care. In that situation, MSI-status will not influence our decision. Otherwise, if this was a stage II tumor and 5-FU was the adjuvant treatment, some key opinion leaders would not use 5-FU in MSI-H patients. Although, still there is a lot of debate.  


Chanjuan Shi
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 19, 2018 8:52 AM

Course Faculty Response

Question 3: There are two initial screening tests for Lynch syndrome: 1) immunohistochemistry (IHC) for four mismatch repair (MMR) proteins and 2) PCR-based microsatellite instability (MSI) testing.  IHC stains for MMR (MLH1, MSH2, MSH6, and PMS2) proteins are a sensitive and specific way to detect MMR deficiency (dMMR). Loss of nuclear staining for one or more of the MMR proteins indirectly indicates MSI-high (MSI-H). MLH1 and PMS2 form the hMutLα heterodimer, and loss of MLH1 always leads to degradation of PMS2. Similarly, MSH2 and MSH6 form the hMutSα, and loss of MSH2 is always accompanied by loss of MSH6. However, loss of PMS2 or MSH6 usually does not cause the degradation of MLH1 or MSH2, respectively. Deficient MLH1 or MSH2 protein are more common than defective MSH2 or MSH6 in MSI-H colorectal cancers (CRCs). Therefore, MMR IHC results for most MSI-H CRCs are either loss of MLH1 and PMS2  or loss of MSH2 and MSH6. The advantages of MMR IHC include 1) only tumor sample required and 2) identification of possible defective MMR protein(s). The disadvantages includes 1) frequent technical failure, 2) loss of protein expression in some treated rectal cancers, and 3) Heterogeneity in protein expression.

PCR-based MSI testing, a fluorescence-based multiplex PCR assay, directly detects microsatellite instability. Both normal tissue (can be replaced by blood) and tumor tissue are needed for the test. Most laboratories in the United States use an assay with five mononucleotide repeat markers (BAT-25, BAT-26, NR-21, NR-24, and MON)-27) to detect MSI and two pentanucleotide repeat markers (identity markers) to ensure normal tissue and tumor from the same patient.  The results are interpreted as MSI-H (≥2 markers unstable), MSI-Low (1 marker unstable), or microsatellite stable (0 marker unstable). The results from MSI testing are easy to interpret, and it can be used to detect MSI in treated rectal cancers. However, it requires normal tissue and sufficient tumor tissue with a tumor cellularity of at least 20-30%.

MSI-H in CRCs mainly results from 1) hypermethylation of MLH1 gene promotor (sporadic MSI-H CRC) and 2) germline mutations in one of the four MMR genes or EPCAM gene (Lynch syndrome-associated CRC). Deletions in the 3’ region of EPCAM can cause hypermethylation of MSH2, which results in loss of MSH2 expression, consequently dMMR. Majority of MSI-H CRCs are sporadic, and only about one-fourth are Lynch syndrome-associated. While sporadic MSI-H CRCs frequently have BRAF V600E mutation, Lynch syndrome-associated CRCs are always BRAF wild type. For that reason, when a CRC is determined to be MSI-H by PCR or when it shows loss of MLH1 and PMS2 by IHC, analysis for BRAF V600E mutation can  rule out sporadic CRCs. Analysis for MLH1 promotor methylation should also be performed to determine whether it is sporadic or hereditary when a MSI-H CRC shows loss of MLH1 and PMS2 expression and is BRAF wild type (or mutation status unknown). It is recommended to send a blood sample for germline genetic testing for MLH1, MSH2, MSH6, PMS2 and EPCAM when a CRC has 1) loss of MLH1 and PMS2 expression with no MLH1 promotor hypermethylation (and no BRAF V600E mutation), 2) loss of expression of PMS2 alone, 3) loss of expression of MSH2 and MSH6, or 4) loss of expression of MSH6 alone.

Both PCR-based MSI testing and MMR IHC have a sensitivity of approximately 90%.  Nearly 5-10% of MSI-H CRCs could be missed by either test. Therefore, in patients with a high suspicion for Lynch syndrome, if one test shows microsatellite stable, the tumor should be tested using the second method to increase the sensitivity.


ASCO University
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 19, 2018 8:57 AM

Patient Case #2

Age/Sex: 72 years, male

Medical History: Arterial hypertension, diabetes type II

Both are well-controlled under current medication

Family History: Negative

Type of Tumor: The patient was diagnosed with a non-obstructive sigmoid adenocarcinoma with liver metastases in both lobes and several small lung lesions

MTD: The patient presented with a synchronous colon cancer. No indication for surgery at the time of diagnosis. The patient is in excellent condition.

Prior Treatment History/Response:

The MTD decided to start with FOLFOX/anti-EGFR based on left-sided tumor and RAS wild type. The treatment was well tolerated, but unfortunately after 10 months of treatment, the scan showed progressive disease.

Images/Scans/Pathology: Biopsy of liver lesions: metastatic adenocarcinoma, morphologically consistent with colorectal primary.

How tissue was acquired/preserved: Formalin fixed paraffin embedded liver tumor biopsy was used for gene mutational analysis.

Testing Platform/Molecular Profiling: Next generation sequencing of selected genes including KRAS and NRAS

Pre-analytics: Review of histopathology; Unstained sections cut from block for microdissection for tumor enrichment (ensure tumor cellularity >10%); DNA extraction.

Analysis: Mutational testing in CLIA-accredited laboratory with laboratory developed 31-gene “hot-spot” next generation sequencing solid tumor panel.


ASCO University
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 19, 2018 8:59 AM

Discussion Questions

1.    The patient is diagnosed with a metastatic colon cancer. To confirm diagnoses pathology is necessary. Question 1: Which material would you use for further (molecular) pathology analysis?
2.    The material to perform (molecular) pathology analysis. Questions 2: Besides routine histology, which type of molecular testing would the  pathologist do?
3.    After 10 months of treatment with FOLOFOX/anti-EGFR the disease showed progression. Questions 3: What is the next step? Switch to a second-line, test for additional markers, re-biopsy, liquid biopsy?


Anis Toumeh, MD
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 19, 2018 1:51 PM

1- I believe either material (metastatic or primary) can be used 

2- Would test for MSI, RAS and BRAF

3- Would switch to FOLFIRI - BEV if no contraindication and good performance status. Would consider Anto-PD1 if MSI-high 



ASCO University
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 23, 2018 10:40 AM

Course Faculty Response by Dr. Marc Peeters

Question 1 response: To start a given treatment in a patient with a synchronous colon cancer that is not suitable for a surgical intervention, it is advised to order a biomarker status of the patient. RAS and BRAF are mostly determined at baseline. Additionally identifying, which side the primary tumor is on, performance status of the patient, and aim of treatment might drive your decision on first line treatment. 

The patient was in good condition with the primary located at the left side. No mutation was found in the RAS and BRAF genes.

The treatment-strategy in first line: FOLFOX/anti-EGFR. The need of re-biopsy after failing first-line therapy is debatable. If we have information of MSI-status on older material, it is sufficient.

Question 3 response: Since there was widespread, disease in order to obtain a rapid response, FOLFOX-anti-EGFR therapy was started. After progression and with the option to treat this patient with immunotherapy, an additional analysis of the MSI status might influence our strategy in second-line.


Chanjuan Shi
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 23, 2018 10:45 AM

Course Faculty Response

Question 1 response: This case presented with a synchronous, unresectable metastatic CRC. For patients with metastatic CRC, the guideline from ASCP-CAP-AMP-ASCO recommends metastatic cancer tissues as the preferred specimens for molecular biomarker testing when such specimens are available and adequate. Therefore, a liver biopsy is the preferred specimen for molecular testing in this patient. However, several studies on the genes commonly mutated in CRCs (including KRAS and BRAF) have demonstrated high overall concordance rate between primary and metastatic tumors. High concordance rate of MSI status between primary CRC and corresponding metastases has also been reported. Therefore, primary tumor tissue is an acceptable alternative when metastatic cancer tissue is unavailable or insufficient.

Question 2 response: The NCCN guidelines recommend extended RAS (including KRAS and NRAS in exons 2, 3, and 4) and BRAF mutational analysis for all patients with metastatic CRC. Several technologies can be used to detect mutations in these genes. However, many cancer centers in the United States use next-generation sequencing to detect mutations in selected genes including RAS and BRAF (targeted sequencing).

Question 3 response: The patient present here is a 72-year-old male with a negative family history. Based on the NCCN guidelines, screening for Lynch syndrome is not entailed for CRC patients who are ≥70 year old and do not meet the revised Bethesda guidelines.  However, for any patients with metastatic CRC, MSI testing or MMR IHC should be performed to determine MSI status as microsatellite instability is a predictive marker for checkpoint inhibitor immunotherapy. Studies have shown that most of MSI-H CRCs respond to immunotherapy whereas the treatment response is only seen in about 10% of patients with MMS CRCs. MSI-H tumors are highly mutated and contain high load of tumor neo-antigens, hence, they are more likely to respond to immunotherapy. The treatment predictive role of PD-L1 expression has not been established in CRCs.

Either PCR-based MSI testing or MMR IHC can be used to determine MSI status in this setting. However, in patients with synchronous, unresectable metastatic CRC (like this case), small biopsy may be the only specimen available for molecular biomarker testing, and normal tissue is often unavailable. MMR IHC may be more feasible than PCR-based MSI testing.


ASCO University
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 28, 2018 10:00 AM

Course Faculty Summary Response by Dr. Marc Peeters

  • A young patient with a family history of colon cancer needs MSI testing to detect Lynch syndrome
  • With the introduction of immunotherapy in metastatic colon cancer, MSI status is becoming important to detect the patients who’re candidate for this type of therapy


Chanjuan Shi
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 28, 2018 10:02 AM

Course Faculty Summary Response

  • Either PCR-based MSI testing or MMR IHC can be used as an initial screening test for Lynch syndrome. There is 5-10% likelihood of getting false negative result for each test.
  • Majority of MSI-H CRCs are sporadic. Further studies, including analyses for BRAF V600E mutation and MLH1 promotor methylation are done to exclude sporadic CRCs before genetic testing for MMR genes is performed on blood.
  • Microsatellite instability is a predictive marker for immunotherapy in CRC patients. Therefore, MMR IHC or PCR-based MSI testing should be done in patients with metastatic CRC.


ASCO University
Re: Colorectal (February 2018): Molecular Oncology Tumor Boards
Feb 28, 2018 10:06 AM

Thank you to Drs. Peeters and Shi for leading the discussion of this case and also to all of those who contributed to the conversation! The forum is now closed to further comments but users have the opportunity to claim credit on ASCO University by clicking here.

Please check back in mid-April for a new case in this series.