Abstract
BACKGROUND
The incidence of renal cell carcinoma (RCC) is increasing, largely due to the widespread use of crossβsectional imaging. Most renal tumors are detected incidentally as small, asymptomatic masses. To study their natural history, the authors prospectively followed a series of patients with this type of lesion who were unsuited for or refused surgery.
METHODS
Twentyβnine patients with 32 masses that measured < 4 cm in greatest dimension (25 solid masses and 7 complex cystic masses) were studied. The primary outcome was tumor size, which was calculated as volume over time. All patients were followed with serial abdominal imaging, and each mass had at least three followβup measurements. The median followβup was 27.9 months (range, 5.3β143.0 months).
RESULTS
Overall, the average growth rate did not differ statistically from zero growth (P = 0.09; 95% confidence interval, β 0.005β0.2 cm per year) and was not associated with either initial size (P = 0.28) or mass type (P = 0.41). Seven masses (22%) reached 4 cm in greatest dimension after 12β85 months of followβup. Eight masses (25%) doubled their volumes within 12 months. Overall, 11 masses (34%) fulfilled 1 of these 2 criteria of rapid growth. Nine tumors were removed surgically after an average of 3.1 years of followβup because it was believed that they were growing fast. No patient had disease progression.
CONCLUSIONS
Approximately oneβthird of small renal masses that are presumed RCCs grow if they are managed conservatively and are followed with serial imaging. The growth rate is slow or undetectable in the majority of patients. These observations raise the possibility of a period of initial observation in selected patients, particularly the elderly or infirm. Cancer 2004;100:738β45. Β© 2004 American Cancer Society.