Predicting Control of Primary Tumor and Survival by DCE MRI During Early Therapy in Cervical Cancer

Abstract

To assess the early predictive power of MRI perfusion and volume parameters, during early treatment of cervical cancer, for primary tumor control and disease-free-survival. Three MRI examinations were obtained in 101 patients before and during therapy (at 2-2.5 and 4-5 weeks) for serial dynamic contrast enhanced (DCE) perfusion MRI and 3-dimensional tumor volume measurement. Plateau Signal Intensity (SI) of the DCE curves for each tumor pixel of all 3 MRI examinations was generated, and pixel-SI distribution histograms were established to characterize the heterogeneous tumor. The degree and quantity of the poorly-perfused tumor subregions, which were represented by low-DCE pixels, was analyzed by using various lower percentiles of SI (SI%) from the pixel histogram. SI% ranged from SI2.5% to SI20% with increments of 2.5%. SI%, mean SI, and 3-dimensional volume of the tumor were correlated with primary tumor control and disease-free-survival, using Student t test, Kaplan-Meier analysis, and log-rank test. The mean post-therapy follow-up time for outcome assessment was 6.8 years (range: 0.2-9.4 years). Tumor volume, mean SI, and SI% showed significant prediction of the long-term clinical outcome, and this prediction was provided as early as 2 to 2.5 weeks into treatment. An SI5% of <2.05 and residual tumor volume of > or =30 cm(3) in the MRI obtained at 2 to 2.5 weeks of therapy provided the best prediction of unfavorable 8-year primary tumor control (73% vs. 100%, P = 0.006) and disease-free-survival rate (47% vs. 79%, P = 0.001), respectively. Our results show that MRI parameters quantifying perfusion status and residual tumor volume provide very early prediction of primary tumor control and disease-free-survival. This functional imaging based outcome predictor can be obtained in the very early phase of cytotoxic therapy within 2 to 2.5 weeks of therapy start. The predictive capacity of these MRI parameters, indirectly reflecting the heterogeneous delivery pattern of cytotoxic agents, tumor oxygenation, and the bulk of residual presumably therapy-resistant tumor, requires future study.