Bronchiogenic carcinoma should be considered in the diagnosis of all respiratory disorders. Malignancy can mimic virtually all common pulmonary diseases such as tuberculosis, Pneumonia, Lung abscess, atelectasis, localized emphysema, Pleural effusion etc. So how can we give a detailed or differential diagnosis to single it out?
Radiological findings: Radiological findings may be protean. The presence of a circular or irregular shadow in an symptomatic patient may be the only finding. The classical circular shadow is called lesion. In more advanced cases, the lesion may be more extensive. Hilar glands are enlarged. The growth may undergo central cavitation and the resulting abscess shows thick and ragged walls. The presence of hilar adenopathy should suggest the malignant nature of the lesion. Presence of diaphragmatic paralysis along with a hilar mass should strongly suggest the possibility of bronchogenic carcinoma. Other features like collapse, consolidation, localized emphysema, and pleural and pericardial effusion may also be present. Special procedures such as tomography, selective pulmonary angiography, isotope scan may help further. A single peripherally placed “coin shadow” in the lung may be caused by primary or secondary neoplasms, tuberculosis, fungal infections or old scars.
Sputum examination: Hemoptysis is present in many cases and the sputum is typically described as “currant jelly”. Malignant cells may be detected in the sputum by examining after methylene blue staining and this can be confirmed by Papanicolaou’s method. Other diagnositc procedures include bronchoscopy, needle biopsy of palpable lymph nodes in the neck and axilla and scalene fat pad biopsy. The right scalene node should be biosied in cases of lesions of the right lung and the left lower lobe. The left scalene node should be biopsied for left upper lobe neoplasms. Mediastinoscopy and biopsy of abnormal nodes is a more rewarding procedure. When a solitary pulmonary nodule (coin shadow) is detected and diagnosis is not evident, the patient should be followed up to see the progress of the lesion. In general, malignant lesions have a doubling time of 5 weeks to 18 months. More rapid growth is suggestive of inflammatory lesions. Calcification is in favor of non-malignant lesions though this is not always true. When there is strong suspicion of malignancy, diagnostic thoracotomy is indicated.
Management depends on the stage of the tumor on diagnosis, histological type and presence of complications. Treatment may consist of surgery, irradiation and chemotherapy.
When the primary is small and is detected before clinical manifestations develop and there are no metastases, surgical treatment is ideal. Contraindications to surgery include infiltration of the trachea, carina, superior vena cava, recurrent laryngeal nerve paralysis and pleural effusion. Presence of mediastinal nodes and distant metastases are contraindications to surgery. Surgical results are less satisfactory in those cases who have developed symptoms.
Radical radiotherapy is preferred in selected cases. In practices, in the majority of cases radiotherapy is given as a palliative measure in inoperable cases with local spread or distant metastases. Several recent advances in radiotherapy techniques such as split dose radiotherapy, use of radio-sensitizers, and the availability of modern radiation equipment like linear accelerator, betatron, neutron beams and meson beams have made radiotherapy more effective with less hazards. In some centers, radiotherapy is also used prophylactically to the brain to prevent the development of metastases.
It is indicated in 90% of patients with bronchogenic carcinoma. The choice of drugs is based on the tumour histology, facilities for supportive therapy, and tolerance by the patient. Chemotherapy may be used as the sole modality of treatment in advanced cases or as an adjunct to surgery and radiotherapy. Commonly used chemotherapeutic agents are methotrexate, cyclophosphamide, vincristine, CCNU, adriamycin and cisplatin.
Since most of the cases are diagnosed late in the disease, overall prognosis in bronchogenic carcinoma is poor. Asymptomatic subjects detected by investigations have the best prognosis. Next in line are subjects with symptoms referable to the primary tumour with a duration of less than sex months. Metastases in CNS and liver confer a poor outcome. Small cell carcinomas have a poorer prognosis since metastases develop early. In the majority of patients only palliative therapy is possible. Five year survival figures for squamous cell carcinoma vary from 40-50% for stage I to less than 10% for stages III and above.
Bronchogenic carcinoma is at least partially preventable by avoidance of smoking. The risk of cancer comes down quantitatively with the reduction in the number of cigarettes smoked and in those who give up smoking completely the increased risk cancer comes down after a period of about 10 years to reach that in nonsmokers. Occupational exposure to asbestos, environmental pollutants and radioactive materials should be reduced to the minimum and personnel engaged in these industries should receive personal protection.