417 PREDICTING OCCULT MULTIFOCALITY OF RENAL CELL CARCINOMA

Background Multifocal renal cell carcinoma (RCC) has been reported in up to 25% of all radical nephrectomy specimens. Modern imaging tends to underestimate the rate of multifocality. Recognition of multifocality before treatment may guide physicians and patients to the type of intervention and tailor long-term follow-up. Objective Our aim was to develop and assess preoperative nomograms to predict occult multifocal RCC. Design, setting, and participants We evaluated 560 consecutive patients undergoing radical nephrectomy for clinically localized suspected sporadic RCC between 2000 and 2008 in a tertiary center. Clinically manifest multifocal lesions were excluded. Logistic regression models were used to assess the potential risk factors of occult multifocality with and without pathologic variables that may be available with preoperative biopsy. Nomograms were developed and assessed for diagnostic properties. Interventions All patients underwent radical nephrectomy. Measurements Assessments of risk factors for occult multifocal RCC were obtained using regression models and nomograms. Results and limitations The incidence of occult multifocality was 7.9%. Significantly associated predictors of multifocality were male gender, family history of malignancy other than RCC, radiographic size of the lesion, histologic subtype other than clear cell, and Fuhrman grade IV. The two designed nomograms had 0.75 and 0.82 concordance indices, respectively. Conclusions Our data suggest that occult multifocal RCC is more frequently associated with small (2–4cm) renal lesions. Male gender, family history of kidney cancer, histologic subtype, and grade are strongly associated with an increased risk of occult multifocal RCC. The developed nomograms had good predictive accuracy that was enhanced when combined with pathologic variables.