TUMOR SIZE EVALUATED BY PELVIC EXAMINATION COMPARED WITH 3-D MR QUANTITATIVE-ANALYSIS IN THE PREDICTION OF OUTCOME FOR CERVICAL-CANCER

Purpose: Tumor size estimated by pelvic examination (PE) is an importa nt prognostic factor in cervical cancer treated with radiation therapy (RT). Recent histologic correlation studies also showed that magnetic resonance (MR) imaging provides highly accurate measurements of the a ctual tumor volume. The purpose of this study was to: (a) compare the accuracy of PE and MR in predicting outcome, and (b) correlate tumor m easurements by PE versus MR. Methods and Materials: Tumor measurements were performed prospectively in 43 patients with advanced cervical ca ncer. MR and PE were performed at the same time intervals: (a) at the start of RT, (b) after 20-24 Gy/2-2.5 weeks, (c) after 40-50 Gy/4-5 we eks, and (d) at follow-up (1-2 months after RT completion). PE measure d tumor diameters in anteroposterior, lateral, and craniocaudal direct ion, and PE-derived tumor size was computed as maximum diameter, avera ge diameter, and ellipsoid volume. MR-derived tumor size was calculate d by summation of the tumor areas in each section and multiplication b y the section thickness. Tumor regression during RT was calculated for each method as percentage of initial volume. The measurements were co rrelated with local failure and disease-free survival. Median follow-u p was 29 months (range: 9-56 months). Results: Prediction of local con trol: Overall, tumor regression rate (rapid versus slow) was more prec ise then the initial tumor size in the prediction of outcome. MR provi ded a more accurate and earlier prediction of local control (at 2-2.5 weeks, and at 4-5 weeks of RT) than PE (only at follow-up). Based on t he initial tumor size, MR was also better than PE in predicting diseas e-free survival and local control, particularly in large (greater than or equal to 100 cm(3)) tumors. Size correlation: Tumor size (maximum diameter, average diameter, volume) by PE and MR did not correlate wel l (r = 0.51, 0.61, and 0.58, respectively). When using MR measurements as a reference, PE tended to overestimate intermediate-size (40-99 cm (3)) tumors. Conclusion: This preliminary study suggests that increase d precision of tumor volume measurement leads to more accurate and ear lier prediction of outcome in cervical cancer. MR tumor volumetry may be useful as an adjunct to PE in selected cases, and holds the potenti al to impact therapeutic decision-making. (C) 1997 Elsevier Science In c.