Lung Cancer – Diagnosis and Treatment

Lung cancer is the commonest cancer and the leading cause of cancer deaths for both men and women in Hong Kong. The incidence is approximately 3000 new cases a year, of whom over 90% are chronic cigarette smoker. Because early lung cancer usually does not carry symptoms, patients often have locally advanced disease by the time they come to seek medical advice.
　
Chest X-ray and CT scan accurately locate an abnormal lung mass but they do not yield a histological diagnosis which is essential in planning a treatment strategy. Recent advances in video-assisted thoracoscopic surgery have provided a much more patient-friendly approach to diagnosis and treatment of lung cancer. By minimizing trauma to the chest wall, patients who have thoracoscopic surgery experience much less pain and discomfort compared to the conventional thoracotomy approach. Furthermore, many patients who would be considered unfit for sugery in the past could now be candidates for resection.
　
Histologically, primary lung cancer can be divided into small cell lung cancers (SCLC) and non-small cell lung cancers (NSCLC). These two groups have basic differences in biological behaviour and hence the treatments to them are also different. SCLC are aggressive tumors with a tendency to early spread. Hence the mainstay of treatment is chemotherapy with or without the addition of radiation therapy. Over 90% of SCLC are responsive to chemotherapy. Despite so, the prognosis is generally poor with 5 year survival figure under 20%. On the other hand, NSCLC of which adenocarcinoma is the commonest, followed by squamous cell carcinoma and large cell carcinoma accounts for 80% of all primary lung cancers. Treatment includes surgical resection, chemotherapy and radiation therapy depends on the stage of the cancer.

Surgical resection of one lobe or the entire lung depends on the size, location and stage of the tumor and remains the best treatment for early NSCLC. The 5-year survival for patients who had a complete resection of an early tumor ( without any evidence of lymph node spread ) is approximately 80%. This underscores the importance in aggressively investigating any new lung mass incidentally discovered on chest x-ray, as over one-third of them would eventually turn out to be primary lung cancer. These patients are curable if operated upon early. On the other hand, once there is sign that the tumor has spread to the lymph nodes, the prognosis is much poorer. For these patients, surgery in combination with chemotherapy and radiation therapy has been shown to provide the best treatment. However, even with the combination treatment, only about one quarter of these patients is alive after 5 years. Disappointingly, several new chemotherapeutic agents have not made an impact on survival statistics.

Smoking remains the single most important cause for lung cancer. However, despite this known fact for almost half a century, there continues to be an increase in the number of smokers in China, especially among the women. There has been some recent development in mass screening, many of which are in the investigational phase that may hold promise for the future. They are aimed at detecting lung cancer at an early stage and include low dose helical CT scan, fluorescence bronchoscopy, immunostaining of sputum and circulating tumor markets.
　
The article is provided by Dr Anthony P.C. Yim, Specialist in Cardiothoracic Surgery and
Director of Minimally Invasive Centre at Union Hospital

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