Contrast enhanced CT (CE-CT) changes and nephrometry down-scoring of unresectable primary renal cell carcinoma (RCC) tumors in patients (Pts) treated with neoadjuvant sunitinib

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Background: The impact of neoadjuvant sunitinib on CE-CT parameters and nephrometry score of primary RCC tumors remains unknown.

Methods: Retrospective review of baseline and prenephrectomy CE-CT from a prospective phase II trial of neoadjuvant sunitinib (50 mg sunitinib continuous dosing) in unresectable primary RCC tumors with or without metastatic disease. CE-CT parameters and R.E.N.A.L. nephrometry score for each lesion were determined in pts who underwent subsequent surgery. RECIST and MASS criteria were used to assess primary tumor radiographic response. CT changes were analyzed using the sign test and Wilcoxon signed rank test.

Results: Twenty nine pts were enrolled, of which 13 pts (85%M; median age 63y) underwent post-sunitinib resection of 16 primary tumors (3 pts had multifocal RCC). Post-therapy, 88% of tumors had decreased long diameter (median 32% decrease, p<0.001 vs. baseline), 88% decreased attenuation (median 30 HU reduction, p=0.006) and 69% increased necrosis (p=0.001). 56% of tumors had a decrease in nephrometry score (median 1 point decrease; 10 to 9, p=004). At baseline, 81% of tumors were highly complex by nephrometry score; following therapy 46% of the highly complex tumors became moderately complex. At baseline 13 tumors abutted renal hilar vital structures, whereas following treatment 4 tumors demonstrated abutment. Adenopathy decreased (range, 23%-83%) in 4/4 patients with enlarged baseline lymph nodes, with complete resolution in 1 patient. RECIST objective response was seen in 38% and SD in 56% of primary tumors; 1 tumor had PD based on size despite > 95% necrosis. MASS criteria response was favorable 38%, intermediate 62%. Two of four pts had reduction in extent of venous thrombus (1 pt from level 0 to resolved and 1 pt from level IV to II).

Conclusions: Neoadjuvant sunitinib resulted in decreased size/attenuation, increased necrosis of the primary tumor and reduction in lymphadenopathy and venous thrombus in pts who underwent subsequent surgery. Sunitinib reduced the RENAL nephrometry score and facilitated nephrectomy, notably due to impact on tumor proximity to vital structures in the renal hilum.

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