Rare-Cancer Research: Why Shared Data and Basket Trials Matter

Rare, added up, is not rare

Each rare cancer affects few people. Together they affect many. NCI's rare tumor network reports that rare cancers make up about a quarter of all cancer cases.

That is the paradox behind this whole field. One in four people with cancer has a disease that almost no single hospital sees often.

The arithmetic problem

A large trial needs hundreds or thousands of participants. For a cancer diagnosed in a few hundred people a year across the country, that trial cannot be built. Not for lack of will, but for lack of arithmetic.

The results are predictable. Fewer trials. Fewer approved drugs. Treatment guided by case reports rather than randomized evidence. Diagnosis that takes longer, because fewer pathologists have seen the tumor before.

Networks instead of single hospitals

One answer is to pool people and information across many sites. NCI's MyPART network brings together scientists, patients, family members, advocates, and clinicians who work on rare tumors.

It also runs rare tumor clinics at the NIH Clinical Center, where patients and experts meet and learn from each other. Gathering people in one place is itself a research method when the disease is scattered.

The network points to results this approach has produced. Atezolizumab has been confirmed as effective against alveolar soft part sarcoma, a rare sarcoma. Nirogacestat shrinks desmoid tumors, improves progression-free survival, and reduces pain. Selumetinib was approved by the FDA for children with NF1 after an NCI-led trial.

Basket trials sort by gene, not by organ

The second answer changes what a trial enrolls. Instead of grouping people by where the cancer started, a basket trial groups them by a shared genetic change.

NCI describes these as studies that enroll people based on the biomarkers in their cancer rather than the site it began in. Our page on biomarker testing explains what those tests look for.

For a rare cancer, this is often the only route into a clinical trial at all. A tumor type with 200 cases a year may still share a mutation with a common cancer that has a drug already.

What NCI-MATCH showed

NCI-MATCH is the largest US trial built this way. It enrolled 1,201 people across 38 treatment arms.

Rare cancers were central, not incidental. Researchers set out to have at least 25 percent of participants with rare or uncommon cancers. The final figure was higher. About 60 percent had cancers other than colon, rectal, breast, non-small cell lung, or prostate.

NCI's conclusion is carefully worded. People with advanced cancer may benefit from genomic sequencing to help plan treatment. That is a maybe, and it is meant as one.

Where small numbers mislead

Small studies are unstable. Two people responding out of six looks like 33 percent. Add four more people with no response and it drops to 20 percent. Nothing about the drug changed.

Other traps follow the same pattern.

• With no comparison group, there is no way to know what would have happened otherwise.
• People who reach a specialized center are often healthier or better supported than average.
• Striking single cases get published. Failures often do not.
• A percentage without a denominator hides everything that matters.

Ask for the raw counts, not just the percentage.

What still matters most

Getting the diagnosis right comes first. Rare tumors are misidentified more often, and a second pathology opinion is reasonable. Our page on how cancer is diagnosed covers the steps involved, and our guide to finding a rare-cancer specialist covers where to look next.

Ask at the specialist visit

• Has my diagnosis been confirmed by someone who sees this tumor often?
• Is there a registry or network for this cancer?
• Are there basket trials open to my tumor's genetic profile?
• How many people have been treated on this study so far?
• What does the trial measure, and over what period?

How this article was prepared

An AI-assisted editorial system helped prepare this page. No named medical reviewer has reviewed it unless one is listed.

The National Cancer Information Foundation publishes Cancer Explained. This page is for learning. It is not medical advice and does not suggest a test or treatment.

See an error, old source, or unclear wording? Tell us.