Among the modalities for cancer therapy we must basically differentiate between systemic therapies (chemotherapy) and local therapies (surgery or radiation), bearing in mind that the therapeutic options can also be combined with each other.
Systemic Therapies
- With systemic therapy or chemotherapy, a drug - for cancer this is usually a chemotherapeutic drug - is introduced into the blood circulation and subsequently affects the whole organism.
Systemic therapies are used if the cancer has already affected several parts of the body.
In some cases, systemic therapies are also used to reduce the size of the tumour before local therapy is used.
Chemotherapy reaches all regions of the body and has an anti-cancerous effect there. A chemotherapeutic drug must therefore be able to distinguish between healthy and cancerous cells. This distinction if often achieved by using the characteristically enhanced cell division frequency of the growing cancer - and this is why chemotherapy is most effective on rapidly growing tumours. Unfortunately, there are also healthy cells which divide frequently - for example hair cells, the cells of the bowel mucosa and the cells in the haematopoietic system. Chemotherapy does not therefore just kill cancer cells but also rapidly dividing healthy cells.
Another problem is, that Cancer cells can also develop a resistance to the chemotherapeutical drug.
The domains of systemic therapy are diffusely distributed tumours such as leukemia or metastases which can no longer or not yet be diagnosed or localized because of their microscopic size. Finally, systemic therapy is used for solid tumours which cannot be treated by surgery or radiation for technical reasons.
Chemotherapy as sole treatment option will be successful in only 5% of patients. Therefore chemotherapy is mostly used in combination with surgery and radiation therapy (see below) for the treatment of advanced, i.e. already metastasized tumours.
Local Therapies
- For local therapies a distinction must be made between surgery (surgical removal of tumours) and radiation therapy (destruction of tumours by irradiation).
Local therapies are used if the cancer is locally confined. If the cancer has already affected other regions of the body, local therapies can be used to fight the cancer at these sites.
Both of these local procedures can be combined with chemotherapy. This is particularly appropriate if microscopically small metastases also need to be affected in addition to the solid tumour.