Asbestos has been implicated in a number of malignant conditions in addition to mesothelioma. While asbestos induced lung cancer is the most well known, esophageal cancer and renal cell carcinoma have also been positively associated with asbestos exposure.
What is Lung Cancer?
Lung cancer is a cancer originating in the airways of the lung or in the parenchyma, which is the tissue of the lung. Lung cancer is most often fatal. Cigarette smoking is generally thought to be the major risk factor although there are other causes such as asbestos exposure.
What causes Lung Cancer?
It has been proven that cigarette smoke and asbestos play a synergistic or multiplicative role in the development of lung cancer. This means that while smoking and asbestos exposure can both cause lung cancer, combined the risk increases exponentially. Some studies have shown that those who smoke cigarettes and have been exposed to asbestos have a fifty fold increased risk of lung cancer over the non asbestos and cigarette exposed population while those who have smoked cigarettes but who have had no exposure to asbestos have only an eleven fold increased risk.
Lung Cancer has a variety of pathological classifications that are based on the cell type that undergoes the malignant transformation. Pathologists expert in lung pathology are able to categorise it and classify it into one of the classification systems. A simple one is to classify it as a small cell or non small cell lung cancer. Those classified as small cell lung cancers are usually managed medically while the non small cell cancers, if detected at an early stage maybe amenable to surgery.
Non small cell lung cancer is also classified according to size, location and evidence of spread at the time of diagnosis. This classification system is used as a basis of surgical treatment and prognosis. It is called staging and goes from Stage I to IV. The lowest being the best and the stage that is best helped by surgery if the patient is medically fit. Staging now has been greatly assisted by the introduction of PET scanning. This has meant needless surgery can be avoided if tumour spread is shown by the screening.
Lung cancer maybe picked up as a result of an x-ray taken for another reason or it may present because of a complication such as haemoptysis, spread to a surrounding anatomical area which results in pain or nerve involvement or distant spread to brain bone or liver. The majority of lung cancers are inoperable at the time of presentation. Attempts at early screening to improve diagnosis and cure rate have not been shown to be of benefit.
The treatment of lung cancer maybe surgical or medical. Surgical treatment is best carried out by surgeons who specialise in lung surgery. If medical treatment is required then again, this should be undertaken in centres where a multi-disciplinary approach is adopted. A close relationship with a palliative care unit is also important. Lung cancer is one tumour type that is characterised by paraneoplastic syndromes that require particular expertise in their diagnosis and management.
Asbestos and other causes of lung cancer
The main cause of lung cancer is cigarette smoking. This applies particularly to men. There are some women who develop lung cancer and who have never smoked. The effects of passive smoking maybe important in some of these. The effect of smoking makes other causes difficult to detect. This is particularly so when dealing with occupational causes of lung cancer. The International Agency for Research on Cancer has developed a classification system for these carcinogens. Group 1 or known carcinogens contains among others asbestos, hexavalent chromium compounds and nickel and nickel compounds.
The relationship between asbestos exposure to the development of lung cancer has generated a lot of heated debate, although asbestos has been implicated in the development of lung cancer from more than 50 years. The state of play at the moment is that the lung cancer can be attributed to past asbestos exposure if the worker has been exposed to sufficient asbestos, generally in the work place, to have caused asbestosis even if the worker does not have overt evidence of asbestosis clinically, radiologically or on lung function testing. There may be other radiological evidence that supports the past history of exposure.
An occupational history is essential in proving the connection and a physician experienced in the field would be best equipped to do this. A report from an occupational hygienist can be of great assistance. There is a lot of knowledge out there that enables estimates to be made based on known fiber types and measured fiber levels in different industrial settings.
Management of Lung Cancer
The management of lung cancer arising in an asbestos exposed worker is no different from any other lung cancer. People managing patients with lung cancer must be aware of the association with the person’s occupation. If there is even a possibility that it is related to work place exposure then the worker must be made aware of that so they might be able to enquire about possible legal remedies.
The relationship between workplace exposure to carcinogens and tobacco smoking is complex. There are some experts who feel they can apportion the effect. It should not be forgotten that lung cancer, in the majority, is a preventable condition. Our efforts should be directed to achieving that. For those who work in this field the gains have been impressive but there is some way to go; particularly with the lobbying of powerful vested interests.