What a clinical trial is and how to take part if I have colon cancer

How can I join a colorectal cancer clinical trial in Spain?

Reviewed by: Equipo CRC Warriors (pendiente de revisión clínica) Last reviewed: 01/11/2026 Updated: 01/11/2026 3 min
In short: A clinical trial is a study in which a new treatment is compared with the best available treatment, under strict controls. In oncology, placebo is not used instead of standard treatment. Taking part is free and voluntary, and you can leave whenever you want. The usual route is to ask your oncologist and search for open trials near you that match your mutation.

What a clinical trial is (and is not)

It is how medicine checks whether a new treatment is better, equal or worse than the existing one. Every drug used in colon cancer today (oxaliplatin, bevacizumab, pembrolizumab, encorafenib…) arrived through trials. You are not a "guinea pig": before reaching patients a drug has gone through years of laboratory work, and the trial is approved by the Spanish Medicines Agency (AEMPS) and an independent ethics committee.

The phases

  • Phase 1: few patients; finds the safe dose. Usually offered when standard treatments have been exhausted. Many phase 1 trials today involve drugs aimed at a specific mutation (KRAS G12D, HER2…) and can produce meaningful responses.
  • Phase 2: dozens or hundreds of patients; measures whether the drug works in that tumour.
  • Phase 3: hundreds or thousands; compares the new treatment with the standard. This is the one that leads to approval.

What you should know

  • Placebo: in oncology, placebo is almost never given instead of treatment. If there is a placebo, it is added to standard treatment (everyone receives at least the best available).
  • Randomisation: in phase 3, a draw decides whether you receive the new treatment or the standard. Neither your doctor nor you choose.
  • Cost: the drug, the extra tests and sometimes travel are paid for by the sponsor. You never have to pay.
  • Voluntary: you sign an informed consent after reading it calmly, and you can withdraw whenever you want without it affecting your care.
  • Closer monitoring: you will have more visits, blood tests and CT scans than outside the trial. For many patients that is an advantage.
  • Eligibility criteria: each trial requires certain conditions (mutation type, previous lines, general health, liver and kidney function). Not meeting them is not a failure on your part; that trial is simply not for you.

How to find one

  1. Ask your oncologist, always. They know the trials open at your hospital and can refer you to another centre. Ask specifically: "Is there any trial for my mutation/situation, here or at another hospital?"
  2. Search yourself so you arrive at the appointment informed:
  3. Have your molecular profile to hand (RAS, BRAF, MSI, HER2, NGS panel). It is what decides most new trials. If you have not had a broad panel and have exhausted lines of treatment, ask for one.
  4. Contact the centre: each trial record lists the hospital and sometimes a contact. Usually your oncologist makes the referral. If you go on your own, bring reports and images.

What to ask before accepting

  • What is being compared, and what is my chance of receiving the new treatment?
  • What is the trial's aim (cure, extend life, improve symptoms)?
  • What side effects of the new drug are known?
  • How many extra visits and tests will there be, and where?
  • What happens if the treatment stops working or I want to leave?
  • Can I keep receiving the drug after the trial ends if it is working for me?

Frequently asked questions

Do I have to pay to take part in a clinical trial?

No. The study treatment, the related tests and, usually, travel costs are covered by the sponsor. If someone asks you for money to join a "trial", be suspicious.

Could I be given placebo instead of treatment?

In colorectal cancer, not instead of standard treatment. If there is a placebo arm, it is given together with the best available therapy, and this is always explained in the consent form.

Can I take part if I am on treatment right now?

It depends on the trial: some are for first line, others for when you progress. That is why it is worth asking about trials at each change of treatment, not only at the end.

Are there clinical trials for your case?

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Sources

This guide is general information prepared by the CRC Warriors Association (non-profit) from public medical sources. It does not replace the assessment of your oncologist or medical team, who know your case. If you spot an error, write to contacto@crcwarriors.org.