Twenty years ago, talking about cancer was so taboo that people were reluctant to even use the word. Today, due to increased awareness of cancer and improvements in detection and treatment, many people are living longer and feel more comfortable talking about their illness.
Still, the word "cancer" encompasses many different complex diseases and misunderstandings continue to arise. One common source of cancer confusion is the definition of metastastic cancer. Some wonder why a cousin is said to have died of breast cancer when it was actually a tumor in her lungs that lead to her death. In such cases, the primary, or original, tumor began in the breast. But then, cancer cells from that tumor broke off and traveled through the bloodstream to the lungs, where they established a metastastic tumor.
Thus, metastatic cancer refers to cancers that have spread to a site in the body that is far from the original tumor. Sometimes the person will experience symptoms such as pain—particularly when it seeds in bone—while other times it remains concealed and painless.
Below, Dr. Karen Antman, a professor of medicine and pharmacology at Columbia University College of Physicians and Surgeons and director of Columbia's Herbert Irving Comprehensive Cancer Center, explains how metastasis occurs, and treatments for some common metastases.
How would you define metastatic cancer?
Metastatic cancer occurs when the original (primary) tumor spreads to organs in other parts of the body. Some cancer cells break off from the tumor, travel through the blood stream or lymphatic system to another part of the body and invade and then the cells begin to multiply. And before traveling to distant sites in the body, cancer cells may also spread to the lymph nodes near the tumor.
What are some common sites of metastasis?
Cancer cells from much of the body often end up in the lungs, and metastases from within the abdomen often develop in the liver, because those are the first places that the blood passes through on it's way back to the heart. If the cancer cells are not trapped by the capillaries in the lung and liver, they will flow back to the heart and then out into the general circulation to other organs such as the bone, brain and skin.
How do doctors distinguish between primary and metastatic tumors?
Primary tumors in an organ usually resemble the cells in the organ. Metastatic tumors look somewhat like the organ in which the primary tumor developed. For example, a primary lung cancer, which arises in the bronchial ducts, looks different from a breast cancer that spreads to the lung. Also a primary cancer usually arises in a bronchial duct, whereas a metastatic tumor is found out in the air sacs.
Why does cancer often metastasize to the bones?
A lot of the blood percolates through the bones, so certainly tumor cells would end up there. The marrow within the bone has a good blood supply with lots of nutrients and growth factors, making bone marrow a fertile place for tumor cells to grow. So it's a seed and soil situation. The malignant cells can land anywhere but they're more likely to grow if they are in an area that's conducive to growth.
How are bone metastases usually treated?
Most of the time bone metastases are treated with radiation. Most tumors are pretty sensitive and radiation doses can be given that don't hurt the bone but reliably kill the metastatic cells. Radiation very quickly takes away the pain and allows the bone to repair itself and become strong again.
We take X-rays to diagnosis lesions in weight bearing bone and those we are particularly careful about treating those with radiation, as soon as possible, to prevent them from growing big enough to be at risk for fracture. However, if the bone lesion has gotten fairly large, surgeons may need to prevent a fracture by stabilizing the bone with a steel rod or a hip replacement.
Hips are the area where we have to be careful. If you have a big lesion in the femur, generally around the hip, we want to treat that with radiation before it gets big enough to cause a hip fracture. Back pain is another symptom we watch for. A metastasis in a vertebra can jeopardize the spinal cord.
For patients who have had a bone metastasis, bisphosphonates are a group of drugs that strengthen the bone and decrease the number of new bone metastases and fractures that could occur in diseases like breast cancer and multiple myeloma.
Are there any sort of behavioral changes that one can make to prevent fracture?
For patients who may have bone metastases in a weight-bearing bone, physicians recommend avoiding activities that stress the bone, such as picking up heavy things, exercise and even stepping off a bus.
Are people usually monitored for metastases?
That requires a very complex answer. For breast cancer, once someone has a primary lesion and it's treated, the only monitoring that appears to make a difference for survival is a mammogram every year and a physical exam. In other words, there is no real reason for getting bone scans or CT scans every six months because it doesn't change survival rates.
However, any symptoms require immediate evaluation. For bone pain, we would obtain X-rays and scans if appropriate, particularly of weight-bearing bones, because we want to avoid pain and fractures.
We are also particularly careful about back pain from bone lesions. Because the vertebra sit very close to the spinal chord, we want to very quickly make the diagnosis of a metastasis to a vertebra so that you can radiate it and prevent any impingement of the tumor on the spinal chord, which can lead to paralysis.
Monitoring somebody who is not known to have metastases is not recommended in the absence of symptoms, at least for breast cancer. But once someone is known to have metastases, then we monitor.
What are micrometastases?
In a primary tumor, sometimes there will be microscopic areas of invasion of a lymph node or in bone marrow. For example, if you do a biopsy in the bone marrow, a small number of cells can be identified under the microscope with special stains. These cells probably would not have been picked out without this special stain. These aren't big lesions that are growing.
Are micrometases a concern?
It may be a little problematic. The prognosis may be somewhat worsened, but not necessarily as much of a concern as a large metastasis that is clearly growing. If we find a micrometastasis to a lymph node, it makes everybody nervous and therefore we are more likely to recommend additional therapy than we would without these findings.
What if standard treatments are no longer working?
Certainly when you've got a situation where the standard treatment isn't very good, clinical trials are totally appropriate. I generally recommend clinical trials whenever the patient's prognosis with standard treatment isn't wonderful, or where two treatments that are both known to be effective are being compared, so that we eventually know which regimen works better.
How has the outlook for people with metastatic cancer changed over the last decade?
It really depends on which primary tumor it is and how sensitive it is to chemotherapy. Testicular cancers and certain types of lymphomas can be cured even if they are widely metastatic. It's more difficult to control metastatic colon cancer, breast cancer or renal cancer. Removal of a single metastasis is sometimes curative. Otherwise cure as the goal of treatment is not realistic. The goal to keep the disease under control.