What makes a cancer “hard to treat”?


human-skeleton-163715_1280First and foremost, no cancer is “easy to treat”- cancer is a devastating illness that poses many challenges to patients, doctors and researchers. However, relative to one another, some cancers are more difficult to treat for various reasons. For example, certain cancers, like those of the pancreas and ovaries, are very difficult to detect and screen for, so they silently progress to advanced stages. Some are very rare and poorly understood, so treating them is all the more problematic, whereas still others have unique features that make them very resistant to therapy.

The easier a cancer is to detect, the sooner it can be identified, and the easier it is to treat. Many can be detected by the naked eye, such as skin cancer, others, like breast cancer can be felt through the skin and have excellent screening programs in place- these have some of the best prognoses when caught at early stages. Unfortunately, cancers of the internal organs are far more challenging to diagnose since they are hidden away inside the body and screening is not part of routine examination. When symptoms finally do appear, the disease is typically at a very advanced stage. Any cancer that has somehow avoided detection and progressed to late stages is exceedingly difficult to treat- it has had time to accumulate numerous changes that make it particularly aggressive and resistant to drugs, and it has often already metastasized (spread to other sites of the body).

Accordingly, experts agree that early detection is perhaps the single most important element in improving prognoses, making it a top priority for researchers to invent clever new screening methods and strategies. In fact, some tests can now detect nasopharyngeal or lung cancer by simply analyzing a person’s breath! These new screening and imaging technologies have already significantly improved rates of detection and many cancers now have high success rates when caught and treated early.

The next big breakthrough may come from the discovery of small molecules, such as certain proteins or genes, found in the blood that are only present if a patient has a particular disease- scientists call these biomarkers. It is possible to imagine that cancer screening will one day be as simple and routine as a blood test.

Put plainly, anything that is rare is less understood than what is common- we know less about giant squid than we do about horses. Similarly, we know far less about how to diagnose, screen for, or what to expect from some cancers compared to others, making them much harder to treat- cancer of the blood vessels, connective tissue or heart are such examples.

Even once a cancer is detected, it can still be very difficult to treat. The standard of care for most cancers is to surgically remove the initial tumour; a tumour’s location can make this a very challenging undertaking. Surgeries on the brain or in the abdomen pose far more risk than skin tumours and are also much more time consuming and costly procedures. Also, late stage disease is often very aggressive and resistant to drugs.

Researchers working on these rare cancers have other hurdles to overcome as well. There is a lot more public awareness, support and funding directed to common cancers. Once new drugs or therapies are developed, appropriate clinical trials must be conducted to ensure that a drug is safe and effective before it can be brought to the public, simply finding enough patients to complete these trials can be a slow process. However, new technologies are vastly improving what we know about rare cancers. Experimental techniques are constantly being improved to become more and more sensitive, allowing researchers to extract more and more information from small and rare tumour tissue. To overcome the hurdles of studying rare cancers, scientists from around the globe are collaborating and working together to track down and learn what they can from these rare diseases.

One important question that may not immediately come to mind, but researchers must carefully consider, is how to deliver a drug. Drugs are commonly swallowed as a pill, and are carried through the blood stream to the target site. They then exit the blood to reach the tumour and kill cancer cells. Unfortunately, some parts of the body have features that prevent this from happening, such as the blood-brain-barrier (BBB). The BBB can be thought of as an impermeable plastic wrap enclosing individual blood vessels found only in the brain. Its normal function is quite important: it protects a the brain from infections and toxins, but by the same token it makes treating brain cancer notoriously difficult by preventing potentially life saving medication from leaving the bloodstream. Very (very!) recently, researchers from Sunnybrook Health Sciences Centre here in Toronto have discovered a non-invasive way to cross the BBB! They ultrasound technology with small bubbles that can carry drugs, called microbubbles, to show that we can now deliver drugs out of the blood, directly to the tumour, in a controlled way. This is a massive breakthrough for brain cancer treatment and opens up new avenues for research.

Ultimately, cancer is a disease that is simply difficult to treat. Period. However, each day researchers are making headway to overcome the issues that make some cancers all that much more challenging. When we look at how far we have already come, the road ahead looks very promising.

This article was written by Mike Pryszlak. Mike is currently completing his PhD at the University of Toronto. He studies how normal stem cell genes are changed in cancer stem cells. To learn more about Mike and his research check out our members page.

Further reading about the BBB:



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