The diagnosis and management of small (< or = 3 cm) renal neoplasms: a commentary

Recurrent renal cell carcinoma following nephrectomy and ablation therapy: Radiology perspective

Renal cell carcinoma (RCC) is the most common renal malignancy, accounting for approximately 2% of adult malignancies and 4% of new cancer cases in the United States every year. Imaging guided ablative therapy, including radiofrequency (RF) ablation, cryotherapy and microwave has gained popularity over the last decade in treatment of small tumors. Antiangiogenic therapy has set itself to be the standard of care for many patients with metastasis these days. With hope for more research, survival rates of metastatic RCC may increase from a current 2-year survival rate of approximately 20%. Variation in imaging surveillance protocol in terms of frequency, modality, and duration is noted among guidelines developed by several organizations. In this review article, we will discuss follow-up imaging protocols, patterns of RCC recurrence following different modalities of treatment, imaging appearance, as well as usual and unusual sites of metastatic disease.

The natural history of incidentally detected small renal masses

BACKGROUND

The incidence of renal cell carcinoma (RCC) is increasing, largely due to the widespread use of cross-sectional 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

Twenty-nine 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 follow-up measurements. The median follow-up was 27.9 months (range, 5.3-143.0 months).

RESULTS

Overall, the average growth rate did not differ statistically from zero growth (P = 0.09; 95% confidence interval, - 0.005-0.2 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 12-85 months of follow-up. 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 follow-up because it was believed that they were growing fast. No patient had disease progression.

CONCLUSIONS

Approximately one-third 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.