Renal Tumor Size and Presence Of Synchronous Lung Metastasis At Time Of Diagnosis: Implications For Chest Imaging.

OBJECTIVE To quantify synchronous lung metastasis risk based on renal tumor size and determine a renal tumor size threshold to determine when chest imaging is warranted. METHODS We assessed 253,838 patients diagnosed with a renal tumor who underwent staging chest imaging between 2010-2016 within the National Cancer Database. Patients were stratified by renal tumor size in 10 mm increments, and synchronous lung metastasis risk was calculated for each category. Logistic regression analyses were used to test the relationship between renal tumor size and presence of synchronous lung metastasis after adjusting to all available covariables. RESULTS Overall, 14,524 out of 253,838 (5.7%) patients had evidence of synchronous lung metastasis. Median (IQR) tumor size for patients with versus without sLM was 90 mm (65 - 115) vs. 40 mm (25 - 60), respectively. The incidence of synchronous lung metastasis was low for renal tumors <40 mm, without significant change, based on tumor size. Conversely, synchronous lung metastasis increased proportionally to renal tumor size for lesions ≥40 mm. In our cohort, 47% of patients (120,386/253,838) had a renal tumor <40 mm, and 0.9% (1,135/120,386) of these had patients had synchronous lung metastasis. Only 8% (1,135/14,524) of patients with synchronous lung metastasis had a renal tumor <40 mm. CONCLUSION The risk of synchronous lung metastasis increased proportionally to renal tumor size; however, the risk was low for tumors <40 mm. These findings suggest that there may be minimal utility of performing screening chest imaging for patients with renal tumors <40 mm.