RESUMEN
OBJECTIVE: The purpose of this study was to determine the prognostic significance of tumor volume regression rate during radiotherapy (RT) measured by three serial magnetic resonance imaging (MRIs) studies performed in patients treated with RT alone and compare the results with patients treated with concurrent chemoradiotherapy (CCRT). METHODS: We evaluated 81 patients with uterine cervical cancer who underwent three serial MR examinations, i.e., at the start of RT, at 36-45 Gy of external RT and 1 month after the end of RT. Forty-three patients were treated with RT alone and 38 patients were treated with CCRT. Pre-RT tumor volume (V1), the tumor volume regression rate measured during the fourth week of RT and residual tumor volume at 1 month after the end of RT (V3) were determined for each patient. The cut-off value used for the three parameters studied was the one that made the largest outcome difference. These volume parameters were analyzed to determine a difference in the treatment outcome. RESULTS: In the patients treated with CCRT, the mean value of the V1 was larger and the mean value of the V3 was smaller than in patients treated with RT alone. The mean value of the mid-RT regression rate was somewhat higher in patients treated with CCRT than in patients treated with RT alone; however, this difference was not statistically significant (79% vs. 69%). In both the RT alone and the CCRT group, the patients with a mid-RT regression >/=75% had 100% 5-year local control rates and a better disease free survival than the patients with mid-RT regression <75%. The patients with V3=0 cm(3) also had a better 5-year local control rate than the patients with a V3>0 cm(3), but statistical significance was found only in the patients treated with CCRT. CONCLUSIONS: The mid-RT tumor volume regression rate, at 36-45 Gy of external RT, was a predictor of local control rate in both RT and CCRT patient groups. However, in the patients who were treated with CCRT, the local control rate difference was even larger by post-RT residual volume than by the mid-RT tumor regression rate. Further studies on appropriate evaluation timing for mid-RT response in patients receiving CCRT are needed.