Why not radiate extensive stage lung cancer?
Can radiation treatment be used on lung cancer? If so, to what dosage? To all areas of the lung? My father has small cell lung cancer that has responded well to chemotherapy. I'm wondering what would prevent treating his lung tumor with radiation?
Mitchell Machtay, MD, Assistant Professor of Radiation Oncology at the Hospital of the University of Pennsylvania, and Deputy Chairman of Radiation Therapy Oncology Group, responds:
Yes radiation can be used on lung cancer. Medium radiation doses (2000 to 5000 cGy over 1 to 5 weeks) are used for large tumors; higher radiation doses (6000 to 7000+ cGy over 6 to 8 weeks) are used for smaller tumors.
There is a common belief that lung cancer is "resistant" to radiation treatment. This is based on the fact that many patients receive radiation therapy for lung cancer - all too often without success.
In actuality, however, radiation can destroy many types of lung cancer cells, much like breast cancer, throat cancer, or prostate cancer cells. The main reason why radiation fails is that most lung cancers are extremely large and have spread to several (or many) sites in the body by the time they are detected and treated. This is particularly true for small cell lung cancer, a rapidly growing tumor that is quickly fatal if not treated. Fortunately, small cell lung cancer is one of the more "sensitive" types of cancers, meaning that the amount of radiation required to slow it down or kill it is lower than many other types of cancer. Small cell lung cancer is relatively sensitive to chemotherapy as well.
The most important treatment for small cell lung cancer is chemotherapy, since chemotherapy drugs circulate throughout the entire body. In contrast, radiation therapy can be given only to the main tumor in the chest plus some of the nearby tissues that are likely to be infested with smaller tumors. In answer to the 3rd question posed, it would be extremely dangerous to give radiation to a large portion of both lungs, because of the risk of severe and possibly even fatal radiation "pneumonitis" (damage to the lungs). Thus, radiation therapy is usually only used when tests show that the cancer is "limited" to a small or modest-sized area. Small cell lung cancer is considered "limited" if there is no spread of cancer outside of part of one lung plus the lymph nodes within or near that lung. The tumor must be small enough to be hit with a "reasonable-sized" radiation portal beam. If the cancer is indeed "limited," there are clinical studies proving that adding radiation to chemotherapy prolongs survival and increases the chance for long-term cure.
Spread to the opposite lung, the pleural fluid (fluid lining the outside) of the lungs, bones, skin or internal organs outside the chest is considered "extensive" stage disease. You did not mention whether your father has limited or extensive disease. I suspect that if he is not being offered radiation that maybe his cancer is extensive. Radiation treatment is not routinely used for extensive stage disease for several reasons:
- First, even if the main tumor is eradicated by radiation, the other sites of cancer will remain and might continue to spread (some have said that using radiation or surgery for extensive stage disease is like closing the barn door after the cows have escaped).
- Second, the side effects of adding radiation to chemotherapy can be severe and difficult for patients with extensive cancer to tolerate. These side effects include sore throat, loss of appetite, weight loss, fatigue and shortness of breath.
- The clinical studies in extensive stage disease have not consistently shown that radiation improves survival.
Nonetheless, for some patients with extensive stage disease, adding radiation to chemotherapy can offer good palliation and improved quality of life, by controlling distressing symptoms such as pain, coughing of blood or swelling of the neck and face (superior vena cava syndrome).
In summary, the most important factor in determining whether or not radiation is used for small cell lung cancer is whether or not it is "limited." However, this should not be the only factor to consider. For an individual patient, the possible benefits of adding radiation need to be weighed against the possible side effects and risks prior to reaching a decision.