by John Brown

Created on: March 12, 2009

Cancer is not a single disease, but is over 100 related but dissimilar diseases which have common characteristics. These are genetic diseases caused by defects in one or more regions of the cell DNA, in which the normal control mechanisms are absent, and thus cells can divide and grow in an uncontrolled way. Cancers can broadly be subdivided into blood cancers (e.g. leukemias and lymphomas) or solid tumours, which can be benign or malignant. Benign cancers or tumors are localised in one tissue, and are non-invasive, and are usually contained within a membrane. Malignant tumors are not contained like benign tumours, and often migrate to other distant tissues to start another growth or tumour in a process called metastasis. Metastatic tumours give rise to secondary tumours, and when these invade and destroy vital organs, the outcome is bleak.

There are already many approaches to the treatment of cancer depending on the type of disease, the stage (early or advanced in progression), the age and general health of the patient, and whether treatment has previously been administered. Treatments include surgery (for solid tumors where operable), radiotherapy, chemotherapy, immunotherapy and other therapies. The challenge in treatment is that every single cancer cell must be eliminated, otherwise even a single remaining cell has the potential to produce further disease. Surgery alone is not usually sufficient to remove all the cells, so either radiotherapy or chemotherapy is used to remove any remaining malignant cells. And there lies the problem with treatment.

When a solid cancer is diagnosed, there are usually over 1 million tumor cells present. Radiotherapy or chemotherapy will kill most, but not all the cancer cells, and those which remain may become resistant to further treatment. If chemotherapy is used, it is common to use 3 or more different compounds which attack tumours at different stages of the cell growth cycle to ensure maximum cell kill. Cells which survive this multiple drug high dose therapy, often develop into untreatable disease. That said, the success rates against some types of cancer is now approaching 100% for some types of cancer. Sadly some cancers do not respond well to any type of treatment. So some cancers can already be cured.

So what about the rest, can they ever be cured? The simple answer is probably, yes. There have been enormous advances in the understanding of cancer biology in the last 10-15 years, and with advances in molecular biology and the mapping of the human genome, and especially with precise knowledge of the genetic defects which cause the tumors to form, the chances are that effective treatments for all types of cancer will one day be developed.

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