Tiny Sub centimetre Lung Nodules - Risk of early Adenocarcinoma of Lung
In Hong Kong, the incidence of lung cancer is growing gradually. There is some relation to wider detection and longer life expectency. Some other factors remain unknown. Before the Second World War, lung cancer ;as I was told by my medical teacher: is a rare disease. The rapid development of tobacco industry co-incide with the escalating cases of Lung cancer in the West. Thoracic surgeons who used to treat different form of infectious disease, sequealae of pulmonary tuberculosis were burdened with different forms of malignant tumour of the chest.
So the cause of lung cancer growth is definitely related to increase in smoking population, air pollution, urban life style. Since lung cancer is potentially more lethal than other solid tumousr. In male, lung cancer is second highest (next to colon and rectum) in incidence and highest in causes of death among malignant disease. In Female lung cancer is third highest in incidence ( second to breast, colon and rectum) and highest in cause of death. In female and now in young male, adenocarcinoma is highest is frequency.
There has been several proposal of cause of high incidence of non smoking related lung cancer in South Chinese females esp Hong Kong women. One of this is related to kerosene stove or cooking method with exposure to incomplete combustion product in stove. Relation to hormone and Chinese herb or aflatoxin in fermented food or nuts has also been investigated. Genetic markers also has been looked into. No scientific proof or conclusion can be drawn after decades of study.
So screening remains the only method to detect early lung cancer.
Are all minute nodules in CT scan (low dose CT scan for lung cancer detection) needed to be removed ?
This is a difficult question and each case has to be individually assessed and considered.
Surgical risk and ease of small wound resection of the mass needed to be assessed too.
For lung nodules about 6 mm in size. Assume the tumour doubling time is 3 month. Six month later, the volume of the tumour will be quadruple and the diameter fo the nodule will be 1.6 time larger or about 9.6 mm. A normal 5 mm cut CT scan will easily detect the enlargement of the size. Although there is no guarantee of abse3nce of distal metastases, the chance of finding metastaes for primary lung cancer size less than 1 cm is low by restrospective study of clinical cases.
So it may be safe to observe 6 mm nodule with CT scan every 6 months for 2 to 3 years.
For lung nodules larger than 9 mm in size, the chance of being pathological lesion like tumour, benign adenoma, sclerosing hemangioma, hamartoma or secondary lung tumour, granuloma is high. From VATS experience, for peripherally situated 9 mm nodule, more than 70% can be definitely located by digital palpation on lung surface. Excisional biopsy is recommended. For patient age less than 65 without major illness or cardiopulmonary compromise, the risk of VAT lung biospy with excisional wedge resection is minimal and usually required 2 - 3 days of hospitalisation. So I recommend early surgery for that. For deep seated 9 mm nodule, both excisional biopsy by VATS or fine needle aspiration biopsy cytology are difficult. I would recommend observation with 3 monthly CT scan and opt for either Fine needle biopsy if size increases or open wedge resection if patient has high risk (smoker or family history of 2 family member having cancer) of malignancy,
For non well defined nodule or ground glass appearance, I would recommend PET CT scan instead of CT scan alone because measurement of size cause confusion in vague shadow.
For definite solid nodule without characteristics of cancer, PET CT is less helpful to define the nature except for measuring the size change. For granuloma or post infectious change, the PET value or SUV value may be elevated. For broncho alveolar carcinoma, the PET SUV value will be normal.
For lesion less than 6 mm in size, I would recommend either repeating CXR or low dose CT scan in one year time. If the nodule is persistent, work up for lung cancer risk and repeat of CT scan in 6 month time for next 2 years are recommended.
For bilateral tiny nodules, screening for primary and PET CT would be useful. Consideration for millary TB may also be needed. Infiltrative lung disease and intersitial lung disease are also required. The final conclusion will depend on the VAT lung biopsy and resection the dominant nodule ( if present) for histology
The above recommendation is primarily subjective impression a, taking into consideration of guideline from European Society of Respirology 2010 guidelines and American College of Chest Physicians 2006 reommendation for solitary lung nodules. I am experienced cardithoracic surgery with more than 24 years of experience in public hospitals in Hong Kong and private hospital. I welcome any queries or question. Phone: 3160 8865 Dr Chung Shiu Shek