Date Published: December 15, 2012
Publisher: Hindawi Publishing Corporation
Author(s): Rajakumar Nagarajan, Daniel Margolis, Steven Raman, Ke Sheng, Christopher King, Robert Reiter, M. Albert Thomas.
The purpose of our study was to compare the apparent diffusion coefficient (ADC) derived from diffusion-weighted imaging (DWI) of prostate cancer (PCa) patients with three classes of pathological Gleason scores (GS). Patients whose GS met these criteria (GS 3 + 3, GS 3 + 4, and GS 4 + 3) were included in this study. The DWI was performed using b values of 0, 50, and 400 s/mm2 in 44 patients using an endorectal coil on a 1.5T MRI scanner. The apparent diffusion coefficient (ADC) values were calculated from the DWI data of patients with three different Gleason scores. In patients with a high-grade Gleason score (4 + 3), the ADC values were lower in the peripheral gland tissue, pathologically determined as tumor compared to low grade (3 + 3 and 3 + 4). The mean and standard deviation of the ADC values for patients with GS 3 + 3, GS 3 + 4, and GS 4 + 3 were 1.135 ± 0.119, 0.976 ± 0.103 and 0.831 ± 0.087 mm2/sec. The ADC values were statistically significant (P < 0.05) between the three different scores with a trend of decreasing ADC values with increasing Gleason scores by one-way ANOVA method. This study shows that the DWI-derived ADC values may help differentiate aggressive from low-grade PCa.
Prostate cancer (PCa) is the most common malignancy among men in the USA, with an estimated 217,730 new cases and 32,050 PCa-related deaths in 2010 . The incidence of PCa increases with age, and it is very uncommon in men younger than 50 years old. With greater longevity and increased awareness of the disease leading to more men requesting screening, it is to be expected that there will be an increase in the number of patients diagnosed with PCa in the future. Most men diagnosed with PCa ultimately survive the disease and die of other causes. The overall 5-year survival rate is 99% for all stages, but only 34% when there are distant metastases . The aim of PCa management is to identify, treat, and cure patients with aggressive disease that may prove fatal but to avoid overtreating those in whom the disease is unlikely to be life threatening. Most patients diagnosed with PCa have localized disease confined to the prostate. A small number with high-grade tumors will progress to develop local, extracapsular tumor extension and distant metastases.
A total of 44 clinically localized PCa patients who underwent radical retropubic prostatectomy between January, 2007 and May, 2008 were selected for this study. The entire protocol was approved by the institutional review board (IRB), and an informed consent was obtained from each human subject. The ages of the patients ranged from 47 to 75 years, and the patients fell into three different groups by surgery GS: 3 + 3 (mean ± SD, 60.1 ± 6.7 years), 3 + 4 (mean ± SD, 58.1 ± 4.2 years), and 4 + 3 (mean ± SD, 60.3 ± 3.9 years). The mean prostate-specific antigen (PSA) value for the patients with GS 3 + 3, GS 3 + 4, and GS 4 + 3, respectively, were 5.0 ng/mL, 6.8 ng/mL, and 7.4 ng/mL.
Statistical analyses were performed to assess the statistical differences between ADC values for the three different Gleason scores (GS 3 + 3, GS 3 + 4, and GS 4 + 3) using one-way analysis of variance (ANOVA) with SPSS software package assuming parameters were normally distributed. A P value of less than 0.05 was considered to indicate a statistically significant difference. To explore for any relationship between the ADC value, tumor volumes, and the Gleason score, Pearson correlation was performed on the data. Also, analysis of covariance (ANCOVA) was done on ADC values of different Gleason scores with tumor volume as a covariate to see its effect.
The patients mean and standard deviation (SD) of age and PSA and ADC values for tumor PZ regions of three Gleason scores are shown in Table 1. Figure 1(a) shows the T2-weighted MRI of a 68-year-old PCa patient with GS 3 + 4 and Figure 1(b), corresponding ADC map with low signal on the left base PZ. Figure 2 illustrates a box plot of ADC values for PCa in the peripheral zone tissue categorized by the three Gleason scores. In 13 patients with GS 3 + 3, the (mean ± SD) ADC value was 1.135 ± 0.119 mm2/sec using 32 ROIs. In 22 patients with GS 3 + 4, the (mean ± SD) ADC value was 0.976 ± 0.103 mm2/sec using 52 ROIs. In 9 patients with GS 4 + 3, the (mean ± SD) ADC value was 0.831 ± 0.087 mm2/sec using 24 ROIs. Although a statistically significant difference existed between the three groups (P < 0.05), a certain degree of overlap between tissue types was evident. There was no statistical significance between the PSA and patients ages with three different Gleason scores. To increase the accuracy of MRI, a number of authors have used special techniques to study a particular characteristic of the prostate tumor and surrounding tissues such as dynamic contrast-enhanced (DCE) MRI [17–19] and MR spectroscopy (MRS) [20–24]. MR spectroscopy requires a substantially longer examination time than DWI, and, additionally, shimming process and placement of saturation bands during the examination are time consuming. For evaluation of MRS, baseline correction and phase correction have to be performed in some cases. Source: http://doi.org/10.1155/2012/374805