Cancer treatment
Cancer treatments are a wide range of treatments available for the many different types of cancer, with each cancer type needing its own specific treatment. Treatments can include surgery, chemotherapy, radiation therapy, hormonal therapy, targeted therapy including small-molecule drugs or monoclonal antibodies, and PARP inhibitors such as olaparib. Other therapies include hyperthermia, immunotherapy, photodynamic therapy, and stem-cell therapy. Most commonly cancer treatment involves a series of separate therapies such as chemotherapy before surgery. Angiogenesis inhibitors are sometimes used to enhance the effects of immunotherapies.
The choice of therapy depends upon the location and grade of the tumor and the stage of the disease, as well as the general state of the patient. Biomarker testing can help to determine the type of cancer, and indicate the best therapy. A number of experimental cancer treatments are continuously under development. In 2023 it was estimated that one in five people will be diagnosed with cancer at some point in their lifetime.
The primary goal of cancer treatment is to either cure the cancer by its complete removal, or to considerably prolong the life of the individual. Palliative care is involved when the prognosis is poor and the cancer termed as terminal. There are many types of cancer, and many of these can be successfully treated if detected early enough.
Types of treatments
The treatment of cancer has undergone evolutionary changes as understanding of the underlying biological processes has increased. Tumor removal surgeries have been documented in ancient Egypt, hormone therapy and radiation therapy were developed in the late 19th century. Chemotherapy, immunotherapy and newer targeted therapies are products of the 20th century. As new information about the biology of good cancer emerges, treatments will be developed and modified to increase effectiveness, precision, survivability, and quality of life.Surgery
Malignant tumours can be cured if entirely removed by surgery. But if the cancer has already spread to other sites, complete surgical excision is usually impossible. In the Halstedian model of cancer progression, tumors grow locally, then spread to the lymph nodes, then to the rest of the body. This has given rise to the popularity of local-only treatments such as surgery for small cancers. Even small localized tumors are increasingly recognized as possessing metastatic potential.Examples of surgical procedures for cancer include mastectomy, and lumpectomy for breast cancer, prostatectomy for prostate cancer, and lung cancer surgery for non-small cell lung cancer. The goal of the surgery can be either the removal of only the tumor, the entire organ, or part of the organ. A single cancer cell is invisible to the naked eye but can regrow into a new tumor, a process called recurrence. For this reason, the pathologist will examine the surgical specimen to determine if a margin of healthy tissue is present, thus decreasing the chance that microscopic cancer cells are left in the patient.
In addition to removal of the primary tumor, surgery is often necessary for staging, e.g. determining the extent of the disease and whether it has metastasized to regional lymph nodes. Staging is a major determinant of prognosis and of the need for adjuvant therapy. Occasionally, surgery is necessary to control symptoms, such as spinal cord compression or bowel obstruction. This is referred to as palliative treatment.
Surgery may be performed before or after other forms of treatment. Treatment before surgery is often described as neoadjuvant. In breast cancer, the survival rate of patients who receive neoadjuvant chemotherapy are no different from those who are treated following surgery. Giving chemotherapy earlier allows oncologists to evaluate the effectiveness of the therapy, and may make removal of the tumor easier. However, the survival advantages of neoadjuvant treatment in lung cancer are less clear.
Radiation therapy
is the use of ionizing radiation to kill cancer cells and shrink tumors by damaging their DNA causing cellular death. Radiation therapy can either damage DNA directly or create charged particles within the cells that can in turn damage the DNA. Radiation therapy can be administered externally via external beam radiotherapy or internally via brachytherapy. The effects of radiation therapy are localised and confined to the region being treated. Although radiation damages both cancer cells and normal cells, most normal cells can recover from the effects of radiation and function properly. The goal of radiation therapy is to damage as many cancer cells as possible, while limiting harm to nearby healthy tissue. Hence, it is given in many fractions, allowing healthy tissue to recover between fractions.Radiation therapy may be used to treat almost every type of solid tumor, and may also be used to treat leukemia and lymphoma. The radiation dose to each site depends on a number of factors, including the radio sensitivity of each cancer type and whether there are tissues and organs nearby that may be damaged by radiation. Thus, as with every form of treatment, radiation therapy is not without its side effects.
Radiation therapy can lead to dry mouth from exposure of salivary glands to radiation, resulting in decreased saliva secretion. Post therapy, the salivary glands will resume functioning but rarely in the same fashion. Dry mouth caused by radiation can be a permanent problem.
Chemotherapy
is the treatment of cancer with drugs that can destroy cancer cells. Chemotherapy can be given in a variety of ways such as injections into the muscles, skin, artery, or vein, or it can be taken by mouth in the form of a pill. In current usage, the term "chemotherapy" usually refers to cytotoxic drugs which affect rapidly dividing cells in general, in contrast with targeted therapy. Chemotherapy drugs interfere with cell division in various possible ways, e.g. with the duplication of DNA or the separation of newly formed chromosomes. Most forms of chemotherapy target all rapidly dividing cells and are not specific to cancer cells, although some degree of specificity may come from the inability of many cancer cells to repair DNA damage, while normal cells generally can. Hence, chemotherapy has the potential to harm healthy tissue, especially those tissues that have a high replacement rate. These cells usually repair themselves after chemotherapy.Because some drugs work better together than alone, two or more drugs are often given at the same time. This is called "combination chemotherapy"; most chemotherapy regimens are given in a combination.
Since chemotherapy affects the whole body, it can have a wide range of side effects. Patients often find that they start losing their hair since the drugs that are combatting the cancer cells also attack the cells in the hair roots. This powerful treatment can also lead to fatigue, loss of appetite, and vomiting depending on the person.
The treatment of some leukaemias and lymphomas requires the use of high-dose chemotherapy, and total body irradiation. This treatment ablates the bone marrow, and hence the body's ability to recover and repopulate the blood. For this reason, bone marrow, or peripheral blood stem cell harvesting is carried out before the ablative part of the therapy, to enable "rescue" after the treatment has been given. This is known as autologous stem cell transplantation.
Targeted therapies
Targeted therapy, which first became available in the late 1990s, has had a significant impact in the treatment of some types of cancer, and is a very active research area. This constitutes the use of agents specific for the deregulated proteins of cancer cells. Small molecule drugs are targeted therapy drugs that are generally inhibitors of enzymatic domains on mutated, overexpressed, or otherwise critical proteins within the cancer cell. Prominent examples are the tyrosine kinase inhibitors imatinib and gefitinib.Monoclonal antibody therapy is another strategy in which the therapeutic agent is an antibody which specifically binds to a protein on the surface of the cancer cells. Examples include the anti-HER2/neu antibody trastuzumab used in breast cancer, and the anti-CD20 antibody rituximab, used in a variety of B-cell malignancies.
Targeted therapy can also involve small peptides as "homing devices" which can bind to cell surface receptors or affected extracellular matrix surrounding the tumor. Radionuclides which are attached to these peptides eventually kill the cancer cell if the nuclide decays in the vicinity of the cell. Especially oligo- or multimers of these binding motifs are of great interest, since this can lead to enhanced tumor specificity and avidity.
Photodynamic therapy is a ternary treatment for cancer involving a photosensitizer, tissue oxygen, and light. PDT can be used as treatment for basal cell carcinoma or lung cancer; PDT can also be useful in removing traces of malignant tissue after surgical removal of large tumors. In February 2019, medical scientists announced that iridium attached to albumin, creating a photosensitized molecule, can penetrate cancer cells and, after being irradiated with light, destroy the cancer cells.
High-energy therapeutic ultrasound could increase higher-density anti-cancer drug load and nanomedicines to target tumor sites by 20x fold higher than traditional target cancer therapy.
Targeted therapies under pre-clinical development as potential cancer treatments include morpholino splice switching oligonucleotides, which induce ERG exon skipping in prostate cancer models, multitargeted kinase inhibitors that inhibit the PI3K with other pathways including MEK and PIM, and inhibitors of NF-κB in models of chemotherapy resistance.
Another approach to targeted therapy involves simultaneously targeting multiple genes implicated in cancer development. For example, concurrent targeting of Integrin β3 and IGF-1R genes in breast cancer has demonstrated significant downregulation of both genes in vitro, as well as induction of programmed cell death in cancer cells.
A systematic review published in the U.K. Cochrane database found that targeted therapies significantly improve progression-free survival by 35 to 40% in metastatic or relapsed cancer. While the research points to promising clinical outcomes, there is still limited evidence on the long-term effects of targeted therapies in terms of overall survival, quality of life, and severe adverse events.