For many years, doctors have diagnosed cancer according to its location in the body. But thanks to new technologies, researchers are able to look at the inner workings of cancer cells and are starting to think about cancer differently. Cancers that start in the same place can be very different from each other, and cancers that start in different places can have similarities.
This isn’t a completely new idea. Researchers have known for some time that some cancers have subtypes that are different from each other. For example, different kinds of breast cancers are treated differently with therapies that may be targeted towards the unique features of each subtype.
It has been more challenging to find the similarities among tumours that on the surface appear to be very different. However, researchers in California recently published a study that identifies common links among rare cancers, with the aim of improving treatments.
Rare tumours are often challenging to treat
More than 100 different types of cancer exist, and some of are rare, for example those diagnosed in fewer than 15 in 100,000 people. (For comparison, lung cancer is diagnosed in nearly 70 in 100,000 people.) But when considered all together, rare cancers make up about one quarter of all cancers.
Rare cancers pose challenges to doctors: they are more difficult to study, researchers don’t know as much about them, and they are more difficult to diagnose and treat. In fact, rare tumours have a lower survival rate than many other tumour types.
Many different types of cancer fit under the umbrella of rare cancers, but researchers are finding that it may be more important to focus on what is the same in these cancers. Understanding the similarities at the genetic and molecular levels can help to provide information about drugs that could successfully treat the rare cancers.
Targeted treatments improved survival of rare cancers
The researchers analyzed tissue and blood samples from 40 people with rare tumours, representing 20 different types of cancer. They looked for genetic changes and proteins unique to cancer in the tissue or blood.
They found that roughly 93%of the patients with a rare cancer had at least 1 genetic change or cancer-related protein found in another type of cancer that can already be targeted with an available drug. This presented an opportunity to try giving the person a targeted drug matched to the genetic change or protein found in their tumour.
The researchers were able to follow up with 21 patients who received a matched targeted treatment. After treatment, the cancer in more than half of these patients stopped growing or was no longer detectable. When a targeted treatment was available, progression-free survival was much better.
Genetic and molecular features provide critical information about cancer
Cancer is more than where it is located, and the genetic changes and proteins found in tumours can provide more useful information when determining treatments. This may be particularly important for rare cancers.
Identifying similarities in different types of cancer can suggest new ways to treat these tumours. Using therapies matched to the tumour’s genetic or protein features was successful for a number of people in this study. The researchers will be working on confirming these promising results in a larger study so that this strategy can be adopted more broadly.
Eileen Hoftyzer, BSc, and Carolyn Goard, PhD