Chemotherapy is a mainstay of tumour therapy. The current treatment guidelines for prescribing a treatment rests heavily on how a treatment or treatment combination has fared statistically, in terms of rates of cancer comeback and survival without cancer spread. The protocol does not include testing the efficacy of the drug against the unique nature of a person's tumour.
Each person's cancer is unique. Totally unique. There are similarities, but the way in which a person's cancer responds to therapy is a result of that cancer's individual genetics and how those genetics play out in the function of the cancer cells. Two people with the same type of cancer might respond differently to the same treatment. There is now a way of helping to determine which way a person's cancer might respond. It's called chemosensitivity testing. Keep reading...
A term called progression-free survival is used to describe the successful situation in which a person's cancer goes away, and never comes back. That is, it doesn't spread, metastasize. It is the secondary tumour, called a metastasis, that is most often responsible for a fatal outcome, rather than the (first) primary tumour. To go into a bit more detail here, the treatment (surgery, chemotherapy, radiation therapy, other treatments) has not just killed the diagnosed tumour, it has also worked to kill some really sneaky cells that have escaped the tumour. These cells invade the blood stream and can stay there until they're triggered to exit the blood and form a metastasis. These cells, responsible for cancer spread, are called Circulating Tumour Cells, abbreviated as CTCs.
The idea behind chemosensitivity testing of these circulating tumour cells is this: consider a patient with, for example Cancer X. There might be two different treatment options for this patient - Treatment A has been statistically successful in most cases, and Treatment B seems to work in not as many cases, but is perhaps less toxic, or perhaps it works in cases where Treatment A has failed. Chemosensitivity testing is a tool that can be utilised at this point in time. It is possible to find out which treatment works to kill off a person's renegade Circulating Tumour Cells, before the treatment is given to the patient. Using a sample of patient blood, scientists can isolate the CTCs from the patient's blood sample, and simply expose the cells to both treatments. Each patient's cells will respond differently.
Perhaps with Patient X, the first treatment, Treatment A might be the Oncologist's preferred treatment choice. Prior to the start of treatment, the Oncologist and Patient X may decide to test to see how successful Treatment A and Treatment B are at killing the cells that cause cancer spread. Let's say that Treatment A kills more cells than Treatment B does. These results would confirm that Treatment A is indeed the better choice. However, if Treatment B kills more cells than Treatment A, then Treatment B may be the preferred treatment for this patient. Such information is incredibly valuable to practitioners seeking to understand the unique nature of each patient's cancer. Even though Treatment A has been statistically more successful than Treatment B, in the latter case above, it would be in fact Treatment B that might be more successful at decreasing the risk of cancer spread for this particular patient.
In addition to current treatment methods, a clinician and their patient may now choose to test whether the treatment of choice works to kill off these renegade cells. With a simple blood test, a patient's CTCs can be isolated and tested. Chemosensitivity testing tests the capacity a treatment has to kill off these CTCs. If a treatment successfully kills CTCs, the chance of cancer progression and relapse reduces. This entire process takes a lot of the 'wait and see' out of the equation, and helps to increase confidence that the chosen treatment will work to reduce the risk of metastasis.
Patients: For more information about chemosensitivity testing, click here
Practitioners: Pachmann, K et al., (2013) Chemosensitivity Testing of Circulating Epithelial Tumor Cells (CETCs) in Vitro: Correlation to in Vivo Sensitivity and Clinical Outcome, Journal of Cancer Therapy (4) 597-605 - Download article
The purpose of this blog is to provide information for a general audience. It is not intended as personal or professional medical advice, which should be obtained directly from your Healthcare Practitioner.