Natural history of Cancer

The course of a disease is normally described from a very general perspective, so it is often hard to personalise it for a particular case. In medical terminology, this evolution is known as the natural history of a disease. In the case of cancer, it probably makes more sense to talk in terms of stages and crossroads rather than a linear evolution. Crossroads are critical points during the course of the disease which can produce very different outcomes or consequences.

Broadly speaking the following stages can be identified throughout the course of cancer:

• Preclinical phase (without symptoms). Cancer silently develops in the background over a highly variable period of time (depending on each person and tumour type). Screening programmes focus specifically on this stage of the disease. Some types of tumour never produce any clinical manifestations and the patient dies with the cancer, but not because of the cancer. Despite an increase in the diagnosis of certain types of cancer such as thyroid and prostate cancers, scientists have not detected an increase in patient mortality.
• Prediagnosis symptomatic phase. The period from the onset of symptoms until diagnosis tends to vary greatly. The location of the tumour can play a significant role in aiding early identification or, contrastingly, delaying diagnosis due to a lack of specific symptoms.
• Diagnosis. The diagnostic procedure may be straightforward or complicated. In some cases, several tests are required to identify the tumour and confirm its staging. Staging is an important crossroad because it determines the most appropriate type of treatment.
• Treatment phase. Treatment generally corresponds to a very standardised stage in the cancer process, but it is subject to potential complications or crises associated with the actual treatment or the evolution of the disease.
• Maintenance phase. The initial treatment is usually succeeded by a follow-up stage of varying stability. The “crises” may become evident through relapses (new appearances of the cancer) or due to treatment-related complications. The crossroad after the maintenance stage has two different paths: cure or palliative care.
• Long-term survival. Patients who overcome the maintenance phase, although the cancer for which they received treatment is technically considered to be cured, enter into a new chronic stage of the disease. Cancer survivors subsequently have to deal with the aftereffects of the treatment, the long-term complications of these effects and the risk of developing another tumour.
• Palliative care. Active cancer treatment is always combined with elements of palliative care that are applied more intensively in advanced stages of the disease. The natural history of cancer is characterised by long periods of varying stability, with some intercurrent crises, and end-of-life stages that last for a few weeks or months.

The natural history of cancer is characterised by long periods of varying stability, with some intercurrent crises, and end-of-life stages that last for a few weeks or months.