Natural History

The natural history of Lung cancercan be described by breaking down its course of existence into a sequence of a few simple phases based on the way we experience the disease clinically.

Carcinoma of the lung always passes through a pre-detectable phase, beginning with its biological onset (the development of the first frankly malignant cell) and beginning when the disease may first be shown to exist whether through sputum cytology or chest radiography. It has been claimed that by the time a tumor is 10 mm in diameter it has already doubled in size 30 times, contains at least one billion cells, and has completed three-fourths of its anticipated existence. It is likely that during the majority of a lung tumor's existence it will be undetectable by any currently available diagnostic technique.
Most cases of lung carcinoma are felt to enter a phase in which presence of the disease is potentially demonstrable, yet continues to be without symptoms. The disease is detectable if:

The duration of this "presymptomstic-detectable" phase is heavily dependent on the cell type involved and on location of the primary tumor. Sputum cytology can be positive for several years before symptoms occur in a progress from undetectable to unresectable within a few short months. Unfortunately, only about 5% of lung cancer diagnoses are made in this phase. These findings are typically made through incidental X-Ray findings during workup of an unrelated condition of through sputum and X-Ray screening of high-risk patients.

Symptomatic Phase
About 95% of all lung cancer diagnoses are made during the phase when the disease has become symptomatic. Carcinoma discovered at this point in its natural history is almost always well advanced. With very few but significant exceptions, symptomatic lung cancer carries poor prognosis. This is because the vast majority of symptoms in this disease are caused by either locally unresectable or metastatic tumor.