Variation in experts' beliefs about lung cancer growth, progression, and prognosis.
BACKGROUND
Little is known about the natural history of malignant solitary pulmonary nodules (SPN). Experts' beliefs may help fill these knowledge gaps and explain variation in clinical practices.


METHODS
Using a modified Delphi process, we surveyed a group of lung cancer experts about tumor growth, disease progression, and prognosis in patients with malignant SPN. After completing the first survey, experts were given the opportunity during a second survey to revise their responses in light of their peers' beliefs.


RESULTS
The response rate was 100% (14 of 14) for both surveys. There was consensus that disease progression depends on the tumor growth rate, that survival for patients with untreated lung cancer is approximated by a declining exponential function, and that treatment is delayed by approximately 1 tumor volume doubling time (TVDT) in patients who undergo a period of "watchful waiting." Just over half of experts (8 of 14) agreed that lung cancer progresses in three steps (from local to regional to distant disease), whereas 43% (6 of 14) preferred a 2-step model (from local to systemic disease). Likewise, 64% of experts (9 of 14) believed that malignant nodules grow exponentially, whereas 36% (5 of 14) believed that growth is slower than exponential. Experts' estimates of the risk of disease progression during a period of observation lasting 1 TVDT varied from 1 to 50%. Estimates of 5-year survival for patients in whom diagnosis and treatment were delayed by 1 TVDT varied between 40% and 80%.


CONCLUSIONS
There is substantial variability in experts' beliefs about the natural history of untreated, malignant SPN. Different beliefs may be partly responsible for variation in management practices.
Schultz
Ellen M
EM
Center for Primary Care and Outcomes Research (PCOR), 117 Encina Commons, Stanford, CA 94305, USA. emschultz@stanford.edu
Silvestri
Gerard A
GA
Gould
Michael K
MK
D002289:Carcinoma, Non-Small-Cell Lung / Q000473:pathology*; D002983:Clinical Competence; D003697:Delphi Technique; D018450:Disease Progression; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D017063:Outcome Assessment, Health Care / Q000592:standards*; D017410:Practice Guidelines as Topic; D011379:Prognosis; D003074:Solitary Pulmonary Nodule / Q000473:pathology*; D011795:Surveys and Questionnaires; D015996:Survival Rate