Correlation of apparent diffusion coefficient at 3T with prognostic parameters of retinoblastoma

BACKGROUND AND PURPOSE: Pathologic prognostic parameters for retinoblastoma have been defined. Our purpose was to correlate ADC values at 3T with prognostic parameters of retinoblastoma. MATERIALS AND METHODS: This study included 72 children (30 boys and 42 girls, mean age 19 ± 2.6 months) with retinoblastoma. Pretreatment diffusion-weighted MR imaging was performed on a 3T scanner with b factors of 0, 500, and 1000 seconds/mm2. ADC values were calculated and pathologic specimens were analyzed. ADC values of the tumors were then correlated with prognostic parameters, including degree of histologic differentiation, tumor size, bilaterality, choroidal invasion, and optic nerve extension. RESULTS: The mean ADC value of retinoblastoma was 0.49 ± 0.12 × 10-3 mm2/s. The ADC values of well- and moderately differentiated tumors were significantly different (P = .007) from poorly and undifferentiated retinoblastoma. There was also a significant difference in the ADC value among small, medium, and large tumors (P = .015), as well as between unilateral and bilateral retinoblastoma (P = .001), and this was independent of the degree of differentiation. The ADC value was also significantly lower (P = .003) when optic nerve invasion was present. There was no correlation of ADC value with growth pattern or choroidal invasion (P = .640 and 0.661, respectively). The ADC value of retinoblastoma was well correlated with the degree of differentiation of the tumor (r = 0.87, P = .007) and inversely correlated with the size of the tumor (r = -0.68, P = .015). CONCLUSIONS: ADC correlated with some of the accepted parameters of poor prognosis for retinoblastoma and may serve as a noninvasive prognostic parameter for assessment of newly diagnosed retinoblastoma.