When a standardized radiologic threshold of greater than 50% is used, patients with unifocal cystic renal cell carcinoma (cRCC) have an excellent prognosis with active surveillance and following surgical resection, findings from a new study show.

At a median follow-up of 5.4 years (IQR 2.8-7.8), none of the 138 patients in the cohort experienced a tumor recurrence or metastasis from cRCC, and 7 (5.1%) died from non–renal-related causes. When comparing patients who initially underwent surgery to those who were initially managed with active surveillance, the researchers found that there was no significant difference in overall survival (P = .07). There were no deaths due to kidney cancer in the entire cohort.

The terminology of cRCC has historically been used to describe an indolent version of RCC that consists primarily of cysts, and the threshold of cystic involvement has traditionally been greater than 75% cystic on pathologic examination.

However, this classification does not contribute to the preoperative decision-making process, the study authors noted in Journal of Urology .

“Cross-sectional imaging provides the benefit of assessing tumor morphology without surgical manipulation, allowing for an accurate assessment of the solid and cystic components and classification of cRCC ,” write Ari Hakimi, MD, of Memorial Sloan Kettering Cancer Center in New York, and his colleagues.

Studies evaluating radiologic criteria for cRCC diagnosis have suggested that cystic changes in 5%-45% of the total mass observed on imaging are associated with favorable survival. Thus, the authors sought to improve the preoperative assessment of cystic renal masses by evaluating cRCC as an enhancing renal lesion that is greater than 50% cystic on cross-sectional imaging. The goal of the current study was then to compare the long-term outcomes of patients with cRCC who underwent surgery and active surveillance using this hypothesized threshold.

The cohort included 138 patients who underwent surgery at Memorial Sloan Kettering Cancer Center for a renal mass from January 2000 to December 2015, and of this group, 102 (73.9%) had renal cell carcinoma and 36 (26.1%) had benign masses. Most of the tumors were Fuhrman grade 1-2 (77.5%), ≤pT2 stage (83.4%) and clear cell histology (65.9%), while the majority of cRCC lesions were Bosniak 3 and 4 (93.5%) and had a solid component of less than 25% (83.3%). On multivariate analysis, men (P = .007) were more likely to have malignant lesions and Bosniak 3 lesions were more likely to be malignant (P = .01).

In the subgroup of 38 active surveillance patients, 27 (71.1%) remained on active surveillance while 11 (28.9%) subsequently had surgery, of which all underwent partial nephrectomy. The median overall growth rate for lesions was 1.0 mm/year (IQR 0-2.8) over 25.3 months (IQR 16.3-44.8), and no evidence of recurrence or metastasis was reported in any of these patients at a median follow-up of 4.3 years (IQR 2.1-5.7) from first imaging diagnosis or 6.9 years (IQR 4.9-8.5) after surgery.

“We believe that our radiologic definition allows for more inclusive criteria of cRCC and would encourage kidney sparing approaches or implementation of AS protocols when feasible,” the authors concluded.

SOURCE: Hakimi A et al. J Urol. 2018 Feb 26 doi: 10.1016/j.juro.2018.02.3087