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Cancer Therapy

Tumor markers

Tumor markers are substances that are produced by tumors or the body’s response to presence of a tumor. Tumor markers found in various body fluids, such as the blood, can be useful in the detection and response to treatment of certain cancers. However, most tumor markers are not specific for cancer and they may be present or even elevated with benign diseases. The absence of a tumor marker can also be useful in confirming successful cancer treatment; whereas an increase in the tumor marker level may indicate recurrence. Two well known markers are Prostate Specific Antigen (PSA) for prostate cancer and CA-125 for ovarian cancer.

Radiation

It is ironic that the same agent that can cause cancer can be used to destroy cancer, but a common mechanism is at work. Fairly low to moderate doses of radiation can cause DNA damage, which may result in the malignant transformation of normal cells into cancer cells. But, high dose radiation focused on cells can destroy the cancerous cells. However, even with highly focused radiation treatment, normal surrounding tissues are exposed to the radiation and may lead to secondary cancers.

Some terms you will hear about are:

Radiosensitive – cancer degenerates in response to radiation

Radioresistant – the cancer may have a partial response or doesn’t respond at all

Fractionation – a treatment radiation dose is broken down into multiple exposures over several weeks to minimize side effects

Chemotherapy

Perhaps nothing short of surgery strikes fear into our hearts more than being told, “You’re going to need chemo”. Stories of hair falling out and nausea and/or diarrhea are awful. But, the essential action of most chemotherapeutic agents is to kill or stop the development of rapidly dividing cells. However, chemotherapy works systemically (affects the whole body) so any rapidly dividing cell, cancer or not, is affected by the medication; such as hair follicles and the lining cells of our stomach/intestines. Make sense?

Another side effect of chemotherapy is myelosuppression, where the rapidly dividing bone marrow cells are killed off. Patients may complain of extreme fatigue due to anemia (reduced number of erythrocytes) and can be at increased risk of infectious disease (reduced number of leucocytes).

Chemotherapeutic agents that you will likely hear about are: Cisplatin, Carboplatin, Bleomycin, 5-fluorouracil, methotrexate, Vincristine, Vinblastine, and Taxol. Since the same mechanism that kills a malignant cell or blocks development of a malignant cell can have similar effects on a normal, rapidly dividing cell, any of these agents can have unpleasant side effects. Some forms of cancer treated with chemotherapy may cause the cancer to “disappear” for awhile although not cured and the patient may be symptom free sometimes for months or years. This period of holding the cancer in check is called a “remission”. Unfortunately, many such cancers, such as leukemia, reoccur and the patient is said to have “relapsed”.

Every year, promising new treatments are being developed. One of the newest is an angiogenesis (blood vessel growing) inhibitor. Medications such as Avastin and Sutent block blood vessels from growing into a tumor thereby starving the growth.

Surgery

In my opinion, the best way to get rid of a cancer is cut it out. I want rid of it now! However, some tumors are so enmeshed in normal tissues that they cannot be safely cut out without severe damage to normal tissues, in other words, they are “inoperable”. And, depending upon the location (brain, prostate, etc) and the amount of excised tissue, one may be left with severe disability. However, surgery can be a complete cure for some types of tumors if done early, such as malignant melanoma (skin cancer). The probability of a cure may be enhanced after surgery by following up with additional treatments such as chemotherapy, radiation therapy or both. The term for this is “adjuvant therapy”.

Some surgical terms you will hear:

Cryosurgery – destroying malignant tissue by freezing it with a cold probe. Often used for soft tissues like liver or kidney.

Fulguration – “Lightning” in Latin. Malignant tissue is destroyed with an electrocautery instrument (electric current).

Excisional biopsy – simultaneous tissue sampling and removal of a tumor with a safe margin of normal tissue. Frequently done with suspicious skin lesions; example, malignant melanoma.

Resect- to cut and remove a segment of an organ containing a tumor.

En bloc resection – removal of the tumor and any surrounding organs or tissues that may be involved. This is often necessary for large abdominal sarcomas.

Unfortunately, not all cancer treatments are curative. Palliative treatment gives relief of symptoms, but does not cure and is reserved for advanced malignancy.

The following is a simulated patient case.

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