Apparent diffusion coefficient: An associative factor for recurrence after nephrectomy in localized renal cell carcinoma

  • Nishie A
  • Kakihara D
  • Asayama Y
 et al. 
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Abstract

Purpose: To investigate whether the apparent diffusion coefficient (ADC) of a tumor is associated with recurrence after nephrectomy in renal cell carcinoma (RCC) Materials and Methods: We retrospectively studied 49 patients with localized RCC who underwent 1.5T magnetic reso-nance imaging (MRI) including diffusion-weighted imaging preoperatively. Fifteen patients had recurrent disease after surgery. The ADC was measured by placing a region-of-interest in a solid region of each tumor on the ADC map. We named the average value of the three ADC values the " average ADC " and the lowest ADC value among the three as the " minimum ADC. " The correlations between clinicopathological factors including patient age and gender, tumor side, tumor size, growth/invasion pattern, Fuhrman grade, histological subtype, venous invasion, average and minimum ADCs, and disease-free survival were analyzed by Cox proportional hazards model. Results: In univariate analysis, tumor size, venous invasion, mean ADC, and minimum ADC showed significant correla-tions with disease-free survival (P < 0.05). In multivariate analysis, only venous invasion and minimum ADC were signifi-cant (P < 0.05). The 5-year disease-free survival rate of the low minimum ADC group was 51.6%, while that of the high minimum ADC group was 85.1%. Conclusion: The minimum ADC of a tumor, although not as pronounced as venous invasion, was found to be an inde-pendent associative factor for recurrence after nephrectomy in patients with localized RCC. D iffusion-weighted imaging (DWI) provides functional information such as motion and diffusion of water molecules, and it can be used for the detection and charac-terization of lesions 1 . The apparent diffusion coefficient (ADC) is associated with cellular density, tumor grade and the nucleo-cytoplasmic ratio in malignant tumors 2–4 . The ADC has also been associated with outcomes in prostate, endometrial, and head and neck cancers 5–7 . Renal cell carcinoma (RCC) is the most common primary malignant tumor of the kidney. It accounts for 2%–3% of all adult cancers and is the sixth cause of death due to tumors world-wide 8 . Many anatomic, clinical, histologic, and molecular prog-nostic factors for RCC have been reported 9 . The purpose of the present study was to investigate whether the ADC of a tumor is associated with recurrence after nephrectomy in localized RCC. Declaration of Helsinki. The requirements for informed consent were waived for this retrospective study. Based on the medical data recorded at our hospital, 67 patients who underwent a preoperative MR examination and nephrectomy for RCC within 1 month between August 2000 and December 2004 were enrolled. Eighteen patients were subsequently excluded. Seven of the excluded patients had lymph node or dis-tant metastatic lesions preoperatively. Eight patients were not fol-lowed up at our institution. The remaining three patients were excluded because their DWI showed poor image quality or the sequence was not included in the MR examination. As a result, the final subject group consisted of 49 patients with localized RCC. The details of the patient profile and pathological findings are summarized in Table 1. Each patient had only one RCC. The sur-gical methods performed included total nephrectomy in 46 patients and partial nephrectomy in the other three patients. After surgery, chest-abdomen-pelvis computed tomography (CT) was performed for the surveillance of recurrence every 3 or 6 months. MRI

Author-supplied keywords

  • apparent diffusion coefficient
  • diffusion-weighted imaging
  • prognosis
  • recurrence
  • renal cell carcinoma

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