Original article
Preoperative decision making for renal cell carcinoma: Cystic morphology in cross-sectional imaging might predict lower malignant potential

https://doi.org/10.1016/j.urolonc.2013.02.016Get rights and content

Abstract

Objectives

Several histologic studies showed more favorable oncologic outcome for renal cell carcinoma (RCC) with cystic change. However, there is no prognostic tool to judge on cystic RCC preoperatively. We hypothesized, that cystic morphology in cross-sectional imaging predicts lower malignant potential.

Materials and methods

From our prospectively conducted oncologic database, we identified 825 patients who underwent surgery for malignant renal tumors between 2001 and 2010. In 348 cases (42%), adequate imaging was available for an independent review by 2 radiologists. We excluded recurrent and synchronous bilateral RCC, familial syndromes, collecting duct carcinoma, and metastases of other origin. For the resulting 319 patients, we compared clinical, pathologic, and survival outcomes.

Results

Median age was 63 (19–88) years and 220 (69%) patients were male. Median follow-up was 1.7 (0–9.8) years. Of 319 renal masses, 277 (86.8%) were solid and 42 (13.2%) were cystic. In cystic RCC, median tumor diameter was lower (3 cm vs. 4 cm, P = 0.002) and nephron-sparing surgery was more frequent (69% vs. 41.5%, P = 0.002). None of the patients with cystic RCC and 56 (20.2%) with solid RCC had synchronous systemic disease (P = 0.001). The nuclear grade of cystic RCC was more favorable (P = 0.002). Patients with cystic RCC showed better overall (P = 0.049) and cancer-specific survival (P = 0.027). In a multivariate model, only synchronous metastases, positive R status, and greater tumor diameter were independent risk factors (P≤ 0.03).

Conclusions

We report the first study to show that cystic morphology in cross-sectional imaging might predict RCC with a lower malignant potential. This insight could allow less invasive treatment strategies in selected patients.

Introduction

Several clinical scores have been developed to support preoperative decision making on treatment strategies for renal masses [1]. These scores aim at integrating all relevant information from imaging studies like tumor size, polarity, location (anterior vs. posterior), shape (exophytic vs. endophytic), centrality, and closeness to the collecting system [1]. However, the tumor's growth pattern (solid vs. cystic) has not been included yet. This preoperative parameter might be of great importance, as the biological features of cystic renal cell carcinoma (RCC) might cause better oncologic outcome [2], [3].

Up to 15% of clear cell RCCs show cystic change, and especially papillary RCC type 1 tend to form large cysts [2]. There are several rare histologic variants of cystic RCCs that have been introduced as distinct tumor entities to the 2004 WHO classification [4]. Among these, multilocular cystic RCC (MCRCC) has not been reported to show malignant behavior if a stringent definition is applied [2], [5]. However, pathologic and genetic features necessary for exact classification are not available preoperatively [6], [7]. Preoperative imaging provides evidence of macroscopic tumor morphology and some functional aspects like perfusion. For cystic renal tumors, the Bosniak classification provides criteria to assess the share of malignant lesions [8]. But to date, there is no prognostic tool to judge on the oncologic outcome of cystic RCC.

According to previous work [3], [6], [7], [9], [10], we hypothesized that cystic RCC had a lower malignant potential than solid RCC. In our cohort study, we used morphologic features from preoperative cross-sectional imaging to identify cystic RCC [11]. Additionally, we performed a pathologic review of all tumors with cystic morphology to determine the share of MCRCCs. This design discloses the prognostic value of preoperative imaging and adjusts for possibly nonmalignant tumors.

Section snippets

Materials and methods

The Institutional Review Board of the University of Heidelberg approved the study protocol (Vote S-357/2011). Before including patients in our prospectively conducted oncologic database, we obtained oral and written informed consent from them [12]. From this database we identified 825 patients who underwent surgery for radical nephrectomy (RN) or nephron-sparing surgery (NSS) for malignant tumors at our department between 2001 and 2010.

Results

Of 319 renal masses, 277 (86.8%) were solid and 42 (13.2%) were cystic according to preoperative imaging.

Discussion

In our series, preoperative imaging characterizes 13.2% of all malignant renal tumors as cystic masses. This feature predicts improved overall and cancer-specific survival owing to smaller tumor diameter, more favorable grading, and less metastatic disease. These findings might partly be explained by the fact, that by definition [6], [9], [13] the true tumor volume in cystic RCC is at least 75% less than in solid masses [18]. However, in our study, cystic morphology was not an independent

Conclusion

This is the first study to identify cystic morphology in preoperative imaging a possible positive prognostic factor in RCC. This insight might allow less invasive treatment strategies in selected patients. However, larger collectives with longer follow-up are necessary to further assess the true prognostic value of cystic morphology. As the macroscopic growth pattern appears to be relevant for survival, it should be assessed during pathologic workup on a routine base. This rigorous evaluation

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