Preoperative staging of renal cell carcinoma using magnetic resonance imaging: comparison with pathological staging

Role of MRI in staging and surgical planning and its clinicopathological correlation in patients with renal cell carcinoma

Background and Aims:

Radiological evaluation of renal cell carcinoma (RCC) is used for non-invasive staging for better surgical planning. However, the correlation of radiological staging using magnetic resonance imaging (MRI) with histopathological findings has not been done so far. The aim of this study is to assess the role of MRI in pre-operative staging of RCC in patients undergoing radical nephrectomy and nephron sparing surgery (NSS) and correlate it with histopathological findings.

Settings and Design:

This prospective observational study was conducted from February 2015 to October 2016 at a tertiary care hospital in northern India.

Methods:

MR imaging was done on 3 Tesla MR scanner (Signa Hdxt General Electrics, Milwaukee, USA). Preoperative staging was based on 2010 TNM staging system. The preoperative parameters in MRI were tumor size, detection/breach of pseudocapsule, tumor extension into perirenal fat and detection of tumor venous thrombus. The staging on MRI was compared with surgical and pathological staging.

Statistical Analysis Used:

The agreement between these three staging methods was determined using the kappa statistics (0.0-0.2, poor; 0.2-0.4, fair; 0.4-0.6, moderate; 0.6-0.8, good; 0.8-1.0, excellent).

Results:

30 patients with suspected RCC underwent NSS (n = 10) and radical nephrectomy (n = 20). Mean tumor size was 9.66 ± 2.99 cm in the radical nephrectomy group and 4.06 ± 1.16 cm in the NSS group. There was perfect agreement between MRI, surgical and pathological staging for breach of pseudocapsule (κ =1.0, Percentage of Agreement = 100%, P < 0.05). In none of the patients, MRI missed extension beyond the Gerota's fascia or presence of venous thrombus.

Conclusion:

MRI staging of RCC is an accurate predictor of the surgical and pathological stage and has the potential to become a useful tool for preoperative identification of patients with RCC who can undergo NSS.

Renal Masses: Imaging Evaluation

This article illustrates the imaging characteristics of cystic and solid renal masses, along with a summary of identified imaging criteria that may be of use to differentiate masses that are more likely to be benign from those that are more likely to be malignant. In addition, important features of known or suspected renal cancers that should be identified before treatment are summarized, including staging of renal cancer and RENAL nephrometry. Finally, the imaging appearance of patients following treatment of renal cancer, including after partial or total nephrectomy, thermal ablation, or chemotherapy for metastatic disease, is reviewed.

Pretreatment differentiation of renal cell carcinoma subtypes by CT: the influence of different tumor enhancement measurement approaches

PURPOSE

We conducted a retrospective study to evaluate the influence of different tumor enhancement measurement approaches on the ability of computed tomography (CT) to differentiate between solid forms of clear cell renal cell carcinoma (RCC), other RCC histologic subtypes and oncocytomas. Different RCC subtypes have a diverse range of malignant potential; consequently, the information about RCC subtype obtained using minimally invasive imaging method before the treatment could allow the more accurate therapy planning. Differentiation of ccRCCs from oncocytomas is important because oncocytomas are usually benign tumors which could be treated conservatively.

METHODS

CT images of 113 patients with 118 solid renal tumors were evaluated. The imaging protocol consisted pre-contrast and post-contrast images during the arterial and nephrographic phases. Renal tumor attenuation values were measured using region of interest covering as much of the solid enhancing tumor tissue as possible. Tumor attenuation values and tumor enhancement ratios were correlated with histologic subtype. One hundred of tumors were diagnosed as clear cell RCC, nine as non-clear cell RCC and nine as oncocytoma.

RESULTS

Tumor attenuation values of >74 HU on the arterial phase scans significantly correlated with clear cell RCC (Az 0.73). The tumor-to-aorta enhancement ratios calculated on tumor attenuation values measured on the arterial phase scans had a cutoff value of >0.29, which significantly correlated with clear cell RCC (Az 0.79). All ROC curves for differentiating the clear cell RCC from oncocytomas have area under the curve too small (0.5 or less) to have chose cutoff value with sensitivity and specificity that could be applied in clinical work.

CONCLUSION

Enhancement measurements of renal carcinomas on CT images in the arterial phase can be used as an auxiliary method in the pretreatment differentiation of solid forms of the most frequent RCC subtypes in patients not suitable for core biopsy but who are suitable for minimally invasive treatment methods and/or targeted therapy.