What do I really need to know?

There’s a ton of info that you could learn about your tumor — but not all of this information is relevant when it comes to figuring out which treatments are right for you.

So let’s just focus on things that affect your treatment plan. We’ll try to stay away from the really sciency stuff for now, but if you’re interested, we’ll go into the nitty gritty details later on. If you want to know what a term means, check out the glossary!

What do we mean when we talk about treatment?

After you are diagnosed with colorectal cancer (CRC), your doctor will want to discuss how to treat it. This can include surgery, radiation, chemotherapy drugs, or other types of medication.

Depending on the type of CRC you have, treatments you get may vary. In the United States, oncologists make treatment decisions based on their experience and knowledge, as well as the National Comprehensive Cancer Network (NCCN) guidelines. If you want to know more, the NCCN patient guidelines for colon cancer can be found here, and the NCCN patient guidelines for rectal cancer can be found here. Don’t feel like you need to read or understand these documents right now!

For people with early stage colon cancer (stages I, II & III), treatment frequently includes resection (removing the tumor surgically) followed by a minimum of 3 months of chemotherapy (if the tumor has characteristics that indicate that chemotherapy is necessary to get to a cure). Early stage rectal cancer treatment frequently includes radiation too. The information in this section is especially important for those just diagnosed with stage IV cancer, as treatment plans may be less straightforward.

You might have the opportunity to participate in a clinical trial. In clinical trials, researchers can use experimental medications to try and treat your cancer. Some clinical trials test a class of drugs called targeted therapies — meaning people with tumors that have specific mutations may benefit from these treatments. Knowing whether you are in one of these groups can affect your treatment plan.

The very first type of treatment regimen you will undergo is called a “first-line treatment.” There may be very promising first-line clinical trials available for newly diagnosed patients who haven’t yet started chemotherapy. So it’s always good for patients to find out if they qualify for these clinical trials early on.

That’s why it’s so important to know if you fall into one of the groups we’re going to talk about next!

So let's discuss treatment

If you’ve just been diagnosed, there are some things you need to consider. It’s possible to be tested for many different cancer mutations, but not all of them are actionable. Here’s what you need to know.

Just a note, we’ll be going through this super quickly, so you get the essential info you need! Don’t worry if you don’t know what all the words mean, remember that everything will be explained in detail later on.

Is my tumor MSS or MSI-H?

There are two major types of colorectal cancer: Microsatellite stable (MSS) and microsatellite instable (MSI).

These relate to the status of the mismatch repair (MMR) pathway in the cancer cells. Finding out which type of tumor you have can have a big impact on what treatment options are available to you, including clinical trials. Here is a quick summary of each:

Microsatellite stable (MSS) is the “normal” state within our cells where MMR is working as it is supposed to, referred to as proficient mismatch repair (pMMR). MSS is the most common kind of colorectal cancer with MSS being about 85% of all-stage CRC and about 96% of stage IV CRC. The main type of treatment for this type of CRC is chemotherapy.
Microsatellite instability (MSI) is the “mutant” state, where MMR is not working properly and is referred to as deficient mismatch repair (dMMR). MSI is also called MSI-H for microsatellite instability high. MSI-H makes up about 15% of all CRC and about 4% of stage IV CRC. For stage IV MSI-H CRC, the main type of treatment is immunotherapy.

According to the NCCN guidelines, all newly diagnosed CRC patients should get their tumors tested for MSS/MSI-H status given its importance for treatment decisions. If your tumor is MSI-H, then it is recommended that you get tested for an inherited cancer condition called Lynch Syndrome.

If you want to learn more about MSS/MSI-H status, click here.

How do I get my tumor tested for MSS/MSI-H status?

Your oncologist will order one of these tests on your tumor or biopsy tissue to find out if it is MSS or MSI-H. This test typically is covered by insurance, can be done at your hospital and takes 7-10 days to get results. For stage IV CRC patients, when a tumor or biopsy tissue is not available, blood can be used for a liquid biopsy to find out the MSS/MSI-H status of your tumor.

What is the RAS status of my tumor?

All patients with metastatic colorectal cancer (colorectal cancer that has spread from the original tumor site) should have their tumor tested for RAS mutations. Patients with any known KRAS or NRAS mutation should not receive epidermal growth factor receptor (EGFR) inhibitors, such as cetuximab (Erbitux) or panitumumab (Vectibix). In those cases, patients are commonly offered Avastin (bevacizumab), which is an angiogenesis inhibitor.

There are also clinical trials available for patients with RAS mutations. Speak to your healthcare team about clinical trials that you may qualify for.

How do I get my tumor tested for RAS mutations?

RAS testing can be done on tumor tissue using a next-generation sequencing (NGS) panel or by a polymerase chain reaction (PCR) test. Your oncologist may order RAS testing when you are diagnosed.

What is the BRAF status of my tumor?

According to NCCN guidelines, all patients with metastatic colorectal cancer should have their tumor tested for BRAF mutations. The most common BRAF mutation is V600E. Patients who have tumors with this mutation should not receive epidermal growth factor (EGFR) inhibitors, such as cetuximab (Erbitux) or panitumumab (Vectibix), unless given with a BRAF inhibitor.

There are clinical trials in the first-line setting available for patients whose tumors have a BRAF mutation. It is very important that you speak to your healthcare team about first-line clinical trials you may qualify for.

Ask your oncologist about their experience with treating these mutations, as they are rare and it is important to have someone on your team who has experience treating them. You can work with your oncologist to bring specific expertise into your care. Some suggestions on this can be found in the Healthcare Team Roundup.

How do I get my tumor tested for BRAF mutations?

Your tumor can be tested for BRAF mutations through a next-generation sequencing (NGS) panel, or an immunohistochemistry (IHC) test. Your oncologist may order BRAF testing when you are diagnosed.

What is the HER2/ERBB2 status of my tumor?

According to NCCN guidelines, all patients with metastatic colorectal cancer should be tested for HER2/ERBB2 mutations and amplifications.

If your tumor has an HER2/ERBB2 amplification, there may be first-line clinical trials available. Speak to your healthcare team about clinical trials you may qualify for.

How do I get my tumor tested for HER2/ERBB2 amplification?

HER2/ERBB2 testing of your tumor can be done through a next-generation sequencing (NGS) panel, immunohistochemistry (IHC), or fluorescence in situ hybridization (FISH). Your oncologist may order HER2/ERBB2 testing for your tumor when you are diagnosed, if not, it’s good to ask about.

Ready to learn more?

Now we’ve gone over the key details that can affect your first-line treatment, let’s start from the very beginning.

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