Study objectives: To determine the probability of malignancy for a solitary pulmonary nodule (SPN) as a function of cancer history.
Setting and design: Patients who had undergone resection of SPNs at Brigham and Women's Hospital between August 1989 and October 1998 were analyzed. The cohort was split into the following three groups: no history of cancer; history of lung cancer; and history of extrapulmonary malignancy. The histology of the SPN was determined after excision. Logistic regression was used to evaluate the effect of covariates on the probability of malignancy.
Measurements and results: A total of 1,104 patients (55% women; median age, 64 years; age range, 17 to 88 years) underwent removal of 353 benign lesions (32%), 638 non-small cell lung cancers (NSCLCs) [58%], and 113 metastases (10%). Antecedent cancer history was significantly associated with final diagnosis (p < 0.0001), with SPNs being malignant in 63% of patients with no previous cancer, 82% of those with a history of lung cancer (NSCLC, 80%; metastases, 2%), and 79% of patients with history of extrapulmonary cancer (NSCLC, 41%; metastases, 38%). There was no difference in the cause of SPNs between patients with a history of a single cancer and those with a history of multiple cancers. The probability of a benign cause ranged between 62% for nodules < 1 cm to 17% when nodules were > 3 cm, if the patient had no history of cancer (p < 0.0001). The probability of an SPN being benign was cut in half if there was a history of cancer. Among patients with previous extrapulmonary malignancy, age, smoking history, and histology were predictors of diagnosis (p < 0.0001). These variables were used to construct a clinical score to predict the probability of an SPN being a NSCLC or metastasis in these patients.
Conclusions: A history of cancer is an important predictor of the probability of malignancy in new SPNs. Metastases from previous cancer account for almost half of SPNs seen among patients in this subgroup. Diagnosis depends on the histology of previous malignancies, smoking history, age, and size of the SPN.