There is understandable frustration and despair among patients and their families that rare cancers have not received the funding and attention of the more high-profile cancers. They feel left behind by the pink ribbons, the moustaches, and the slip, slop, slaps.
Recent announcements on new funding and clinical trials initiatives are welcome and, in time, will drive real improvements to people's lives. But even when funding is secured, researchers working on rare cancers (or any rare disease) still face significant hurdles.
Finding patterns in genetic or drug response data are made much easier and the insights more powerful when a larger number of patients or samples is available to study.
With rare cancers it is not always possible to get more than a handful of precious samples to work on. Experimental models may be even harder to come by and clinical trials present a real challenge.
Although — it's important to point out that even rare cancer researchers are often at a significant advantage, compared with those working on other rare diseases like motor neuron disease.
Taken individually, rare cancers represent very small numbers of patients — often just a few hundred cases worldwide every year. But together they represent a large proportion of total cases.
A rare cancer is defined as a type of cancer that has an incidence of less than six cases per year, per 100,000 population.
A less common cancer is defined as one that has between six and 12 incidences per year per 100,000 population.
About 42,000 people are diagnosed with a form of rare or less common cancer in Australia every year. Examples are brain tumours, thyroid cancers, liver cancers, pancreatic cancers, kidney cancer, testicular cancer and many, many more.
But the very definition of cancer is changing. The way we currently classify different types of cancer is largely anatomical — based on where in your body the cancer arises. Our various organs are built from hundreds of different cell types, each with specialised function. Any of them can transform into a cancer cell: acquiring the ability for uncontrolled growth, disrupting normal function, even invading and spreading to other organs.
Much of our understanding of cancer pathology, and hence the way we treat it, is built around this cellular or tissue origin model.
The way we think about cancer is undergoing a slow but radical transformation.
Definitions are changing but not funding
The explosion of ever-cheaper, faster and more sensitive technology to read our genome — our genetic blueprint — has driven the emergence of entirely new fields of molecular oncology and precision medicine.
Scientists are moving away from broad definitions — breast cancer, prostate cancer, lung cancer and so on — as genetic data emerges showing that each patient's cancer is unique.
More targeted treatment of the disease is blurring the lines between cancer types.
But funding models, charities and lobby groups, research institutes and medical specialties linked to individual cancer types remain deeply entrenched.
As this new thinking gradually translates into the clinic, we are seeing remarkable improvements in patient outcomes for many of the most common cancer types like breast, prostate and skin cancer. But that success is not universal. Survival rates for many cancers, like brain, lung and pancreatic are shockingly low and have barely shifted in decades. For many patients and their families, the lofty expectations of precision medicine are just a precursor to profound disappointment.
The genomics revolution is driving a shift away from anatomical definitions towards classifications reflecting shared molecular features (i.e. signatures of genetic mutation and gene expression) between tumours in different parts of the body (eg. shared mutations in pancreas and breast cancer).
This biological framework underpins many of the new generation of targeted therapies, such as the breakthrough leukaemia drug Venetoclax. But this revolution could have a profound impact on our understanding and ability to treat rare cancers.
Sequencing genomes isn't enough
The more we learn at the genetic level, the more each individual cancer begins to look like a "rare cancer", and this might show the way forward. With the emergence of molecular oncology and precision medicine, we should be able to leverage the mountains of knowledge we have amassed on more common cancers to improve our understanding and treatment of rare cancers.
Much of the insight we gain into the behaviour of cancer cells with a particular molecular/genetic signature should hold in other rare cancer types with similar molecular profiles.
In fact, the very first cancer drug approved on the basis of application to a molecular signature regardless of anatomical site was approved last year in the US.
But just sequencing genomes is not enough. We also need to do the slow, difficult work of figuring out what those genes do, how they interact with each other in huge, complex and dynamic networks, and how those networks are disrupted in disease. Only then can we really exploit the avalanche of genomic information to realise its therapeutic potential. I worry that the increasing focus on sequencing genomes is drawing our attention away from the truly difficult task of functional translation.
And we need to be careful to balance the expectations generated by the huge hype around precision medicine against the sobering reality that we are not there yet. Despite the creeping evangelism in this space, the reality for most patients today is that we still have a long way to go.
Dr Darren Saunders is an Associate Professor in Medicine at the University of New South Wales.