A small trial has matched patients with rare cancers to treatments based on the characteristics of their disease.

The findings highlight the potential of personalised medicine for these cancers.

Around half of patients who received treatment on the trial saw their tumours stop growing, shrink or disappear completely.

This the first trial to test making treatment choices for rare cancers based on features of the disease, said the researchers. The approach could “open the doors to new treatments” for these patients, said lead researcher Dr Shumei Kato, from the University of California San Diego Moores Cancer Center.

Personalised or targeted medicine involves using specific, often genetic, information about a person’s cancer to help diagnose, treat and find out about how well treatment is working.

The findings have been published in The Oncologist.

Rare cancers – such as sarcomas and anal cancers – are classified as those affecting fewer than six in 100,000 people each year, although some set this figure at fewer than two  in 100,000 people. They can also be defined as rare if they start in an unusual part of the body.

Clinical trials on rare cancers can be difficult due to the small numbers of eligible patients. And this has meant that few targeted treatments have been developed specifically for these diseases.

In the latest trial, researchers studied 40 patients at the Rare Tumour Clinic at the UC San Diego Moores Cancer Center with various rare cancers, including sarcomas and cancers that could not be classified.

They used blood and tissue samples to analyse the tumours’ molecular and genetic features, looking for those which could be targeted with drugs.

Based on this analysis the team identified suitable drugs for just over half of the patients, including immunotherapy. Of the patients who received treatment, more than half (52.4%) saw their cancers stop getting worse, shrink or disappear. And in patients who were previously given standard treatment, the tailored treatments kept patients’ cancers at bay for longer.

Dr Nischalan Pillay, a Cancer Research UK-funded sarcoma expert from University College London, said: “Rare cancers make up around a quarter of all cancers, but these patients are often not eligible for traditional clinical trials because of difficulties recruiting sufficient numbers. This small study provides a way to pursue personalised treatment for these patients.

“There is an urgent need to develop new ways to design clinical trials for patients with sarcomas and other rare cancer types. The design of this particular trial, where recruitment is based on the molecular characteristics in a patient’s tumour rather than on the tumour type, is one way of addressing this. In order to fulfil the promise of personalised medicine more of these kinds of trials should be undertaken.”

The team has now adopted a personalised medicine approach in their Rare Tumour Clinic and plan to carry out further studies with more patients.