A. MONOCLONAL ANTIBODY-DRUG, ANTIBODY-TOXIN, OR ANTIBODY-RADIONUCLIDE CONJUGATES
These antibodies recognize specific antigenic determinants on cancer cells. Their potential is very far reaching. Monoclonal antibodies that recognize tumor associated surface components can deter tumor cell proliferation in culture and whole animals. Administration to patients has been tried recently but only limited success has been achieved so far. By themselves monoclonal will be useful in clearing circulating tumor cells from blood and in clearing the bone marrow of tumor cells. Monoclonal antibodies can also be conjugated with antitumor drugs, toxins, or radionuclides that will allow targeting of the toxic substances precisely to the tumor cells while sparing for the most part the normal cells.
B. BIOLOGICAL RESPONSE MODIFIERS
These incorporate agents like interferons, interleukins that affect the patient�s biological response to a neoplasm beneficially. Some of the agents in this category act directly on the tumor cell while most of them act indirectly by enhancing the host�s immunological response to the neoplastic cells. Recombinant DNA technology has greatly facilitated the production of these compounds. These agents include growth factors, agents increasing differentiation and interferons and interleukins.
C. ADOPTIVE IMMUNOTHERAPY
This is a line of attack in which cells with antitumor activity are administered to a tumor-bearing host and intercede either directly or indirectly the regression of established tumor. This has been approached in several ways. One idea is to take the person�s own lymphocytes and activate them in vitro with appropriate activating factors and then inject them back into the patient. In this approach, the lymphocytes are incubated with recombinant IL-2 which stimulates a population of lymphocytes that when activated can lyse fresh, noncultured, natural killer cell-resistant tumor cells but not normal cells.
D. HEMATOPOIETIC GROWTH FACTORS
Several growth factors have recently been found to be very useful in reducing some of the bone marrow toxicity associate with the use of the anticancer agents. These are a subset of regulatory polypeptides of the cytokine family that are concerned in the proliferation and differentiation of granulocytes and monocyte/macrophages. The ones most commonly used are granulocyte-macrophage stimulating and granulocyte stimulating factor. Both of these have been shown to replenish peripheral blood neutrophils after high dose chemotherapy followed by autologous bone-marrow transplantation. Positive benefits include decreasing the frequency of infections and shortening the stay in the hospital. Erythropoietin has been used to replenish red blood cells in aplastic anemia and after cancer chemotherapy.
E. INDUCTION OF TUMOR CELL DIFFERENTIATION
This therapy take advantage of the capacity to initiate the differentiation of certain kinds of cells into functioning cells rather than allow them to stay in their immature form.
F. GENE THERAPY
This method works by altering the cell�s gene dosage for specific genes, which could significantly affect the outcome of a malignant growth.
G. ANTISENSE THERAPY
This is another approach to regulating gene expression in cancer cells. An antisense piece of DNA or RNA is introduced into the cancer cells. Generally introducing a small piece of DNA into the cell does this. This oligo is complimentary to the normal gene. Such an approach might be used to inhibit the expression of cancer-associated genes if it could be directed towards cancer cells. This approach has worked well with in vitro cultured cancer cells.
H. TUMOR VACCINES
Vaccines may avert the onset of cancer for those tumors initiated or promoted by infectious viruses. These vaccines would be resulting from inactivated viruses or from a preparation of viral antigens. However, vaccination of patients who already have cancer would be much more difficult to accomplish successfully.
I. PHOTODYNAMIC THERAPY
Photodynamic therapy is a treatment for some types of cancer. This is based on the finding that certain chemicals known as photosensitizing agents can kill one-celled organisms when the organisms are exposed to a particular type of light. PDT destroys cancer cells through the use of a fixed-frequency laser light in combination with a photosensitizing agent.
In PDT, the photosensitisizing is injected into the bloodstream and absorbed by cells all over the body. The agent remains in cancer cells for a longer time than it does in normal cells. When the treated cancer cells are exposed to laser light, the photosensitisizing agent absorbs the light and produces an active form of oxygen that destroys the treated cancer cells. Light exposure must be timed carefully so that it occurs when most of the photosensitisizing agent has left healthy cells but is still present in the cancer cells.
J. CRYOSURGERY
Cryosurgery (also called cryotherapy) is the use of extreme cold to destroy cancer cells. Traditionally, it has been used to treat external tumors, such as those on the skin, but recently some physicians have begun using it as a treatment for tumors that occur inside the body. Cryosurgery for internal tumors is increasing as a result of developments in technology over the past several years. For internal tumors, liquid nitrogen is circulated through an instrument called a cryoprobe, which is placed in contact with the tumor. To guide the cryoprobe and to monitor the freezing of the cells, the physician uses ultrasound to spare nearby healthy tissues. Cryosurgery often involves a cycle of treatments in which the tumor is frozen, allowed to thaw, and then refrozen. The treatment can be safely repeated and may be used along with standard treatments such as surgery, chemotherapy, and radiation. Furthermore, cryosurgery may offer an option for treating cancers that are considered inoperable or that do not respond to standard treatments.
K. LASER THERAPY
This therapy involves the use of high-intensity light to destroy cancer cells. This technique is often used to relieve symptoms of cancer such as bleeding or obstruction, especially when the cancer cannot be cured by other treatments. It may also be used to treat cancer by shrinking or destroying tumors. Lasers are used to treat many types of cancer. Laser surgery is a standard treatment for certain stages of glottis (vocal cord), cervical, skin, lung, vaginal, vulvar, and penile cancers. In addition to its use to destroy the cancer, laser surgery is also used to help relieve symptoms caused by cancer (palliative care). For example, lasers may be used to shrink or destroy a tumor that is blocking a patient's trachea (windpipe), making it easier to breathe. It is also sometimes used for palliation in colorectal and anal cancer.
L. LASER INDUCED INTERSTITIAL THERMOTHERAPY
Laser-induced interstitial thermotherapy (LITT) is one of the most recent developments in laser therapy. LITT uses the same idea as a cancer treatment called hyperthermia; that heat may help shrink tumors by damaging cells or depriving them of substances they need to live. In this treatment, lasers are directed to interstitial areas (areas between organs) in the body. The laser light then raises the temperature of the tumor, which damages or destroys cancer cells.
