What are conventional cancer therapies (standard therapies)?

Complete tumour removal is the first and most important goal of conventional cancer treatment. Conventional cancer treatment consists of the three “classical pillars” of surgery, radiation and chemotherapy, which are often combined. There are decades of experience with these methods worldwide. The efficacy of chemotherapeutic agents in particular has been repeatedly tested in clinical trials.

Surgery

For most types of cancer, surgery is the most important form of treatment. It ranges from a small incision to remove a suspicious skin lesion, to extensive surgery. Surgeons remove not only the entire tumour, but also lymph nodes and surrounding tissue. If the tumour can be completely excised, this is always done “within a surgical margin”. This means that the tumour is removed with a small margin of healthy tissue in order to reduce the risk of tumour cells being left behind.

If lymph nodes are affected, these are also removed. Often the lymph nodes surrounding the tumour are also removed as a precaution. Tumours can occur in any part of the body and sometimes may be difficult to access surgically. In such cases it can make sense to reduce tumour size through chemo- or radiotherapy before operating. In this approach, the chemotherapy or radiation treatment is called “neoadjuvant”.

Conversely, a tumour that cannot be completely removed surgically can first be reduced by surgery in order to provide a better starting point for subsequent chemotherapy or radiation therapy. Wherever possible, physicians use methods that will only cause minor injury to the skin and soft tissues. These procedures are called “minimally invasive.” Only a few small incisions are made to insert tubular instruments (this procedure is called “endoscopy”), containing a camera and tiny surgical instruments. This way of operating is also known as “keyhole surgery”. Some endoscopic procedures can be performed without a skin incision at all, such as the removal of colon polyps during a colonoscopy. However, such small operations are not always the method of first choice as the aim of cancer surgery is the best possible removal of the tumour.

The “three classical pillars” of cancer treatment are often combined to optimize treatment outcome. If radiation therapy or chemotherapy is performed after surgery, this is called “adjuvant” (supportive) treatment. Its purpose is to ensure that the tumour and any tumour cells are completely removed.

Radiation therapy (Radiotherapy)

Radiation is another therapeutic strategy in conventional medicine to destroy the tumour. It is applied and acts only locally in the irradiated tissue. Radiation damages the DNA cells. As opposed to healthy tissue, tumour cells are unable to repair these damages and die off. Radiation therapy can be applied following surgery in order to destroy any remaining cancer cells. In some cases, radiation is applied to tumours that are not accessible to surgery. Other types of localized tumours may be treated by radiation therapy alone. Palliative radiotherapy is used to relieve pain and other symptoms of advanced cancer.

Many different types of radiation are used in cancer treatment today: X-rays, gamma radiation, and electron radiation are just a few. They all share the ability to damage the body tissue they penetrate. Medical specialists (radiologists and nuclear medicine specialists) will therefore devise an individual radiation plan for each patient with the aim to ensure the best possible effect on the tumour while minimizing the damage to the healthy tissues.

It is impossible to predict if a patient will expect side effects from radiation. The radiation effect depends on the dose, the size of the irradiation field and the sensitivity of affected tissue. A patient’s general condition and the state of progression of the tumour also have an effect. Radiation damage is suffered primarily by the skin, which will react to radiation with symptoms similar to sunburn. Irritation, redness, tanning effects, and hair loss in the irradiated areas are the most common undesirable side effects of radiation therapy. Many patients experience fatigue and a general feeling of illness with loss of appetite, fatigue or headache after a few days. However, most symptoms disappear quickly after treatment ends, as healthy tissue is able to heal the radiation damages.

Chemotherapy

The third pillar of conventional cancer therapy is chemotherapy with certain drugs known as cytostatics. The word “cyto” stands for “cell” and “static” for “stop,” indicating that cytostatics can stop cells from multiplying. They also have a “cytotoxic” effect, meaning that they act in a toxic manner on rapidly dividing cells.

Tumour cells multiply faster than healthy cells. This is where the active principle of chemotherapy comes in: Cytostatic drugs damage the DNA of cells that are in the process of dividing and multiplying. However, this means that healthy tissues with a higher rate of cellular division than others will experience side effects from chemotherapy. Oncologists supervising chemotherapy protocols will therefore try to specifically affect tumour cells through the precisely calculated combined application of cytostatic drugs while minimizing the impact on the healthy body cells.

In certain types of cancer and especially in those that do not form solid tumours (e.g., leukaemia or Hodgkin’s lymphoma), chemotherapy has proven to be extremely effective. While there are often significant side effects from cytostatic drugs during treatment, the prospects for cure can be very good.

As cytostatic drugs primarily attack cells that frequently divide and renew themselves, healthy tissues with similar characteristics like the hematopoietic system, hair root cells, skin cells and mucous membranes are particularly prone to experience side effects.

Side effects are also the reason why some physicians carefully weigh the use of chemotherapeutic agents. Ultimately, it must be a shared decision between patient and the treating physician. In addition to the physical side effects, patients may experience impairments such as fatigue, chronic exhaustion and depression. These may last for years after chemotherapy and are thus referred to as late effects. Nevertheless, chemotherapy has a firm place in cancer treatment.

Anti-hormone therapies

Hormones or messenger substances control important processes in the body, for instance blood sugar levels, reproduction or growth. Some tumours also grow under the influence of hormones. This can be the point of action of an anti-hormone therapy. Anti-hormone therapy by block the body’s own hormones or keep them from interacting with the tumour, thereby blocking its growth.

Examples:
Breast cancer cells often grow in response to female hormones. These are primarily oestrogens and in some cases progesterone, which will bind to specific receptors on the tumour cells, signalling them to multiply.

Various anti-hormonal therapies can either suppress the body’s own hormone production or prevent their action by blocking hormone receptors on the cancer cells.

Anti-hormones are administered as tablets or by injection and are thus distributed throughout the body. In this way, they are able to reach tumour cells that may have gone undetected during examinations and prevent them from growing. Like chemotherapy, hormonal therapy is a “systemic” treatment, i.e. it is effective throughout the body.

Use of anti-hormonal drugs depends on several factors, like for example, the stage of the disease. It must also be determined whether a patient’s tumour cells react to hormones at all. The report of the findings will then state, for example, the tumour to be “hormone receptor-positive”. Hormone withdrawal

is also a treatment option for prostate cancer, the growth of which is promoted by the male hormone testosterone. However, since at least at the beginning of the disease in all men the tumours grow in a hormone-dependent manner, there is no need for targeted receptor determination – unlike in women with breast cancer.

Targeted therapies

Different tumours can have different characteristics and properties. For example, tumour cells are often stimulated to divide by special substances produced naturally in the body, such as so-called growth factors. These substances are part of specific molecular signalling pathways that responsible for growth, metabolism or the blood supply to the cells. Targeted therapies intervene in such processes and inhibit the metabolism or cell division of the cancer cells. For this purpose, prior to treatment, it is determined whether the tumour has the characteristics suitable for a targeted therapy. Since healthy cells can have these specific characteristics as well, side effects can also occur with targeted therapies.

There are a large number of different targeted drugs that are used to treat a wide variety of cancers and may be combined with other therapies for this purpose.

Immunotherapies

Immunotherapies do not target cancer cells directly, but rather help the body’s immune system fight the cancer. Cancer cells often change in such a way that they are no longer recognized by the immune system and can therefore continue to grow and spread. Other cancer cells actively suppress the activity of the immune system. Immunotherapies are designed to reactivate the body’s immune defences against cancer cells.

Monoclonal antibodies

Antibodies are protein molecules that bind specifically to structures the immune system identifies as foreign or somewhat “altered”, so-called antigens, and designate these structures for destruction by the immune cells. Monoclonal antibody therapy uses artificially produced antibodies directed against specific proteins on the surface of cancer cells, thereby inhibiting their growth. One such antibody is trastuzumab. It binds to the Her-2/neu receptors, which are binding sites for growth factors present in the cancer cells of 25% of women with breast cancer.

Immune checkpoint inhibitors are also monoclonal antibodies.

Immune checkpoint inhibitors

A recently developed group of pharmaceuticals can target specific checkpoints, the “brakes” or “checkpoints” of the immune system. These checkpoints normally prevent the immune system from overacting against healthy cells. However, some tumours can activate such “immune checkpoints” thereby suppressing the activity of immune cells that could actually recognize and fight the tumour. So-called “checkpoint inhibitors” stop this mechanism, enabling the immune system to once again attack the tumour with greater vigour.

Cytokines

Cytokines are messenger or signal substances that have a stimulating or inhibiting effect on the immune system. Cytokines such as interferons or interleukins are also used in cancer therapy. They can inhibit tumour cell division or activate certain immune cells. With cytokine therapies, it has been possible to treat some forms and situations of disease successfully. However, they are increasingly being replaced by other, more effective immunotherapies.

Tumour vaccines

In recent years, various therapeutic vaccination strategies against cancer have been developed. The goal is to train the immune system to better recognize and attack cancer cells by exposing it to cancer-specific molecules, so-called tumour antigens, in a vaccination in order to prevent the growth of tumour tissue.

However, since such vaccines are difficult to develop, current strategies aim to give patients only fragments of such antigens hoping their immune system will respond in the desired way. In most cases, very small proteins, so-called peptides (peptide vaccines), are used. Most of the vaccines for cancer therapy are still in the clinical trial phase.

Prophylactic tumour vaccines are used to prevent the development of certain types of cancer. Examples include the HPV (human papillomavirus) vaccine to prevent cervical cancer, or the hepatitis B vaccine to prevent hepatocellular carcinoma.

CAR-T cells

CAR-T cells (chimeric antigen receptor T cells) are the body’s own immune cells that are genetically modified in a lab in order to recognize and attack cancer cells based on specific target structures, the tumour antigens. After preparation in the lab, the CAR-T cells are reintroduced into the patient’s body via an infusion. CAR-T cell therapy is currently used to treat leukaemia and types of lymphoma. It is a very complex and expensive therapy.