Making Sense of Cancer Therapies

February 19, 2019

Proven approaches and new technologies mean individualized treatment for cancer.

Surgery

Scientists continue to learn more about cancer’s biology and how it affects each patient. As they make new discoveries, they are able to refine existing treatments and develop new ones.In many cases, can be used to remove the tumor and, depending on the pathology of the cancer, the surrounding tissue. In some circumstances, patients might be eligible for less invasive surgical options.

Laparoscopic surgery requires one or more small incisions that allow a thin fiber-optic scope, called a laparoscope, and specially designed surgical instruments to be inserted into the body to remove the tumor. Disease-free survival and recurrence rates for specific tumor types and stages seem to be about the same with laparoscopic surgery compared with traditional open surgery. The main benefits are faster recovery times, shorter hospital stays and fewer complications.

Robot-assisted surgery could have even more benefits for some patients. As with laparoscopic surgery, robot-assisted procedures require a few small incisions. But instead of directly manipulating the surgical instruments, the surgeon sits at a console to perform the procedure by directing robotic arms. The process enables finer movements yet prevents the surgeon from feeling the tissue in the same way as open surgery. In addition to prostatectomy (surgery to remove the prostate gland), robot-assisted surgery can be used for hysterectomy to treat cervical and endometrial cancers, and to treat some bladder, throat, thyroid and kidney cancers. When performed correctly by well-trained surgeons in appropriate patients, robot-assisted procedures have the potential to prevent some short-term complications, such as blood loss, and to reduce the length of hospital stays, compared with open surgery.

Radiation Therapy

Compared to traditional radiation therapy, which can kill cancer cells but also damage healthy tissue, specialized techniques deliver radiation to the tumor more precisely, with less severe side effects.

Proton Beam (left) The larger size of a proton particle, used in specific cases, ensures that the bulk of energy is deposited exactly at the tumor site, allowing more precise treatment and, in some cases, treatment of areas previously radiated with standard radiation.

X-ray Beam (center) X-rays are high-energy photons created by machines, and although the beam can be aimed at a tumor, the radiation dose is also delivered to healthy tissue in front of and behind the tumor. The energy breaks DNA bonds, causing cell death.

Stereotactic Radiosurgery Stereotactic radiosurgery uses highly focused x-rays or gamma rays that originate at many different angles and intersect at the tumor site. The tumor is hit with a high, concentrated dose of radiation, sparing surrounding healthy tissue from the full dose.

Radiofrequency ablation, or RFA, is an outpatient procedure that uses heat delivered through a thin, needle-like probe inserted into the tumor to kill tumor cells. Cryoablation is a similar procedure that uses rapid freezing and thawing to kill the cancer cells.Radiation therapy might be used alone to treat some cancers but is most often used in combination with other therapies to improve the cure rate following surgery. Radiation could also be used to allow less extensive surgery or to relieve side effects of advanced cancer. High doses of radiation can cause side effects after treatment, as well as late effects, such as secondary cancers. Newer specialized techniques more accurately target radiation to tumors and minimize these effects.

Types of Targeted Radiation Therapy

Brachytherapy radiates the cancer cells directly by implanting radioactive seeds or wires into the body in or near the tumor. Brachytherapy is used in prostate, cervical and other cancers. Brachytherapy can also be used in breast cancer. This is a type of partial breast irradiation and is sometimes used for smaller, lymph node—negative, lower-risk breast cancers.

Radiopharmaceuticals are agents that contain radioactive elements that deliver radiation directly to tumors. These injections are approved to treat bone metastases in prostate and thyroid cancers, as well as some types of lymphoma, and to alleviate cancer-related bone pain.

TO THE BONE AND BEYOND: Blood-forming (hematopoietic) stem cells can be harvested from the bone marrow, drawn from the circulating (peripheral) blood or taken from blood in a newborn’s umbilical cord and placenta.

Conformal radiation uses several weak radiation beams originating from different angles that intersect to produce a concentrated high dose of radiation at the tumor site. Advanced conformal therapy, such as intensity-modulated radiation therapy (IMRT), uses multiple beams with varying intensity.

Stereotactic radiosurgery, such as Gamma Knife, uses a computer to simultaneously focus about 200 small beams onto a tumor in the brain while the patient’s head is immobilized in a special helmet. A similar technique, known as CyberKnife, bypasses the need for the helmet by using imaging to make adjustments for movements. Gamma Knife is used for small- to medium-sized tumors in the brain, and CyberKnife is employed for larger tumors and tumors in other areas of the body.

Chemotherapy

Proton beam therapy uses positively charged particles, called protons, that only travel a certain distance. The method allows doctors to control the depth of radiation more precisely and deliver more of it to tumors while sparing nearby healthy tissue. Proton beam therapy is used for some childhood cancers and certain cancers of the brain, central nervous system, eye, head and neck, liver and lung, and some sarcomas. It’s also being investigated in other cancers, such as breast, esophageal and prostate. More research is needed to determine if side effects are less intense than with older types of radiation.While surgery and radiation target the tumor, chemotherapy targets the whole body systemically through a number of mechanisms of action. New chemotherapy drugs are more effective and less toxic than first-generation agents developed 50 years ago, due to greater knowledge about how to deliver them, including optimal dose and frequency of dose, alone and in combination.

A VARIETY OF METHODS ARE NEEDED to attack the numerous ways cancer cells multiply, spread and survive. By combining agents that use different strategies, scientists are gaining ground on cancer.

Angiogenesis: Proteins, such as VEGF, are secreted by cancer cells to signal blood vessel growth to the tumor. Anti-angiogenic drugs block these proteins and starve the tumor of nutrients.

Hormones: Hormones spur the growth of hormone-dependent breast, ovarian and prostate cancers. Hormonal agents cut off the effect of hormones on cancer cells by either lowering hormone levels or blocking receptors.

Growth factors: Growth factors signal the cell to continue multiplying at an abnormal rate. When targeted agents bind to these growth factors or their intended receptors, the pathway is halted or turned off.

Proliferation: DNA contains the cancer cell’s instructions to multiply and resist death. Chemotherapy targets the DNA of these fast-growing cancer cells, stopping proliferation and causing cell death.

Metastasis: It only takes a small percentage of cancer cells to break away from the tumor and invade other organs via the bloodstream or lymph system. Methods to block cell mobility and ultimately prevent metastasis are under way.

Chemotherapy can be given as the primary—or main—treatment for some cancers, such as lymphoma and leukemia. It can also be given after the cancer has been removed as adjuvant therapy, which might improve survival and delay or prevent disease progression. Neoadjuvant chemotherapy is given before surgery to shrink tumors enough to permit less extensive surgery. When cancer is not curable, palliative chemotherapy can often reduce symptoms caused by tumors and help people live longer.

Classes of Chemotherapy Agents

Antimicrotubule agents disrupt mitosis, a phase of cell division in which a cell duplicates and separates the chromosomes in its cell nucleus. Mitotic inhibitors include taxanes and vinca alkaloids (which are approved to treat some solid tumors, as well as lymphomas and leukemias) and epothilones (which are used to treat advanced breast cancer when taxanes no


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