Correlations of UICC tumor stage and tumor regression on T2-weighted MRI sequences during definitive radiotherapy of cervical cancer.

ABSTRACT

BACKGROUND: The purpose of this study is to detect a correlation between the preradiation tumor staging and the relative volumetric regression of the primary tumor through external beam radiation therapy (EBRT). METHODS: Clinical data of 32 patients with a mean age of 60±12 years treated with primary radiation therapy (RT) of cervical carcinoma were analyzed. Union Internationale Contre le Cancer (UICC) stages were T1 = 4 patients, T2 = 15 patients, T3 = 8 patients, T4 = 5 patients; N1 = 26 patients, N0 = 6 patients; and M0 = 25 patients, M1 = 7 patients. All patients received pelvic magnetic resonance imaging (MRI) before RT as well as during RT. The cervical primary tumor was delineated as gross tumor volume (ptGTV) in T2-weighted MRI sequences. We compared ptGTV reduction by stage, lymph node status, metastatic status, and grading. RESULTS: Mean ptGTV reduction during RT was 61.4±28.9%. T1 tumors shrank by 88.2±13.4%, T2 by 67.6±28.7%, T3 by 50.8±23.6%, and T4 by 38.7±27.2%. The difference in tumor shrinkage was statistically significant between the lower T stages and the higher T stages (p < 0.05). There was no statistical difference in the mean ptGTV before treatment in the group with lymph node metastases (LNM) (54.1±47.7 cm3) as compared to the group without LNM (76.6±52.2 cm3). Nonetheless, ptGTV shrank significantly differently by 68.9±25.7% (N1 patients) and by 29.0±17.7% (N0 patients). No significant differences in ptGTV shrinkage were observed in M0 versus M1 and G2 versus G3 tumors. CONCLUSION: There is a correlation between mean ptGTV reduction during EBRT and tumor stages. Tumors with higher T stages shrank less under radiation treatment, and the ptGTV of N1 patients responded better than that of N0 patients.