My father was diagnosed with bronchioloalveolar carcinoma with bone metastasis. He passed away very quickly. He was told that this type of cancer does not respond to chemotherapy. Can you tell me why this type of cancer is so unresponsive? Also, is this a rare type of lung cancer and what are thought to be the causes of this in a non-smoker?
Barbara Campling, MD, Medical Oncologist, responds:
Please accept our condolences to you and your family after your father's death. Bronchioloalveolar cancer (BAC) is a relatively uncommon lung cancer (about 3% of cases), and it is a type of "adenocarcinoma" (which as a group constitutes the most common category of "non-small cell" lung cancer). The behavior of bronchioloalveolar cancer can be quite unpredictable, ranging from a slowly growing indolent but progressive tumor to a rapidly growing cancer, which can be quickly fatal. In fact, it has more recently been shown that there are at least five distinct subtypes of bronchioalveolar cancer that each has a distinct prognosis, so the term BAC is no longer exists, and instead it has been replaced by the names for each subtype that has been identified. Although localized bronchioloalveolar cancers can be cured with surgery or radiation therapy, this tumor is generally considered very difficult to treat. This is partly because it may arise in multiple locations within the lung. Many oncologists believe that certain types of bronchioloalveolar cancers are more resistant to chemotherapy and radiation than other types of non-small cell lung cancer, although there is little evidence for this in the medical literature. The large published studies in non-small cell lung cancer generally do not analyze treatment outcomes according to the histologic subtype, and even if they did, BAC would likely constitute a small subgroup that it would make it difficult to make definitive comparisons.
Why would one type of lung cancer be less responsive than other varieties? There are a number of mechanisms by which tumor cells can resist the effects of drugs and radiation therapy. A few examples include the increased expression of certain membrane proteins which actively export chemotherapy drugs out of cells, increased detoxification of drugs, decreased expression of the drug target, or increased repair of drug or radiation-induced damage. The cause of BAC is not known, but unlike most other forms of lung cancer, it is not consistently associated with smoking. There is a type of lung cancer that occurs in sheep (called Jaagsiekte, or ovine pulmonary adenocarcinoma), which looks very much like human BAC under the microscope. This peculiar disease of sheep is known to be caused by a virus. However, there is no definite evidence that human BAC is caused by a virus, and there is no evidence that it is contagious.
In your father's case, the cancer had already spread to bone at the time of diagnosis. Chemotherapy is often used in the management of metastatic non-small cell lung cancer, and although it is not curative treatment, in some cases it may make patients feel better and live longer than they would without treatment. Nevertheless, response rates to chemotherapy in metastatic non-small cell lung cancer are not very gratifying, typically less than 30%. Furthermore, in patients who are very sick, chemotherapy has not been shown to be beneficial and can actually make them sicker. This may have been a consideration in why your father's physician did not recommend chemotherapy.