We think of lung cancer in two different categories: small cell lung cancer and non-small cell lung cancer. They behave quite differently. We consider small cell lung cancer a systemic disease. It represents about 25 per cent of lung cancers. It is rarely localised but spreads via the bloodstream early in its natural history. It can present with symptoms common to all lung cancers, such as breathlessness, chest pain or cough, sometimes with blood in the sputum. It may also present with symptoms from sites to where it has spread. Small cell lung cancer can produce hormones that give symptoms remote from the cancer. These can include everything from retaining fluid in the body to weakness and skin rashes.
Small cell lung cancer is very responsive to chemotherapy, such as cisplatin and etoposide, but relapses again. Even with disease that is limited to the chest and responds completely to chemotherapy, the average survival is only 18 months, and only 5-10 per cent of patients survive for five years and are considered cured. Survival may be improved a little by irradiating the main site of disease in the chest. Some relapses occur in the brain even if all the rest of the disease has responded. This suggests that the chemotherapy may not penetrate the brain as effectively as other areas. Irradiating the brain can prevent relapse there but does not improve survival and has side effects of its own.
Non-small cell lung cancers include several different types of cancer which tend to remain localised to the lung for longer in their natural history and are thus potentially curable by surgery. If localised to the lung without spread to the lymph glands in the centre of the chest then aggressive surgery is warranted. This may involve removal of part of a lung or the whole of a lung if the individual is fit enough to survive with one lung.
For very early disease, five-year survival rates of 45 per cent have been reported. For more extensive disease that can be encompassed in a radiation field without excessive damage to surrounding normal tissue full-dose radiotherapy alone will cure 5-10 per cent.
Recent research into the treatment of disease that involves some nodes in the centre of the chest on the same side as the cancer suggests that combining the treatment modalities of surgery, radiotherapy and even chemotherapy can improve survival. Radiotherapy in shorter courses can be very effective in controlling the symptoms of pain or cough if a cancer is blocking a bronchus. Local techniques where radiation sources can be placed inside an airway have been useful for local control of the cancer.
Blocked airways can also be relieved by use of a laser during bronchoscopy or the insertion of expanding sleeves into a narrow area which spring open and stent the airway open to counter the compression from a cancer.
In widespread disease chemotherapy has been disappointing. In the last few years, however, more drugs with activity against non-small cell lung cancers have been identified. The taxanes, gemcitabine and navelbine are being combined with platinums to give response rates of more than 50 per cent. Unfortunately, however, although there have been some gains, the improvement in survival in most trials is only weeks to months. Quality of life questions, particularly while on chemotherapy, become important here.
Like small cell lung cancers, non-small cell lung cancers can have remote effects that are not due to metastases. Squamous cell lung cancers can produce a hormone which elevates the blood calcium and causes dryness, drowsiness and constipation — these can be difficult to distinguish from symptoms that are directly due to the tumour. This situation can easily be reversed with simple treatments and so should be investigated. Another remote effect which seems odd is the so-called clubbing or enlarging of the fingernails or toenails, often associated with painful forearms or legs.
A feature of lung cancer which it shares with many cancers is that outcome and survival depend very much on how well a patient is at the time of diagnosis. This is independent of the treatment used and can guide the decision about whether treatment will be worthwhile. Patients who have lost .more than 10 per cent of their body weight in the months before presentation would be expected to survive only half the length of time of those who have maintained their weight. Those who are bedridden will do badly and aggressive treatment will not be helpful.