Velocity of tumor spontaneous expansion predicts long-term outcomes for diffuse low-grade gliomas.

BACKGROUND Supratentorial diffuse low-grade gliomas present a slow macroscopic tumor growth that can be quantified through the measurement of their velocity of diametric expansion. We assessed whether spontaneous velocity of diametric expansion can predict long-term outcomes as a categorical variable and as a continuous predictor. METHODS A total of 407 adult patients with newly diagnosed supratentorial diffuse low-grade gliomas in adults were studied. RESULTS The mean spontaneous velocity of diametric expansion before first-line treatment was 5.8 ± 6.3 mm/year. During the follow-up (mean, 86.5 ± 59.4 months), 209 patients presented a malignant transformation, and 87 died. The malignant progression-free survival and the overall survival were significantly longer in cases of slow velocity of diametric expansion (median, 103 and 249 months, respectively) than in cases of fast velocity of diametric expansion (median, 35 and 91 months, respectively; P < .001). In multivariate analyses, spontaneous velocity of diametric expansion as a categorical variable (<4, ≥4 and <8, ≥8 and <12, ≥12 mm/year) was an independent prognostic factor for malignant progression-free survival (P < .001; hazard ratio, 3.87; 95% confidence interval [CI], 2.67-5.52) and for overall survival (P < .001; hazard ratio, 4.62; 95% CI, 2.58-7.97). Velocity of diametric expansion was also an independent prognostic factor for overall survival as a continuous predictor, showing a linear relationship between overall survival and spontaneous velocity of diametric expansion (hazard ratio, 1.09 per one unit increase; 95% CI, 1.06-1.12; P < .001). CONCLUSIONS Independent of the molecular status, the spontaneous velocity of diametric expansion allows the identification of rapidly growing diffuse low-grade gliomas (at higher risk of worsened evolution) during the pretherapeutic period and without delaying treatment.