Correlation between the treated volume, the GTV and the CTV at the time of brachytherapy and the histopathologic findings in 33 patients with operable cervix carcinoma

Abstract

Background and purpose: This study correlates the treated volume, the GTV and the CTV at the time of intracavitary brachytherapy (BT) with the histopathological findings obtained by surgery (S) in 33 patients (pts) with cervix carcinoma.

Patients and methods: Sixteen pts (group I), FIGO stage IB1 (1), IB2 (4), IIB (10), IIIB (1), received external beam radiotherapy (EBT) with a total dose of 45 Gy in 5 weeks and concomitant CISPLATIN 40 mg/m(2) weekly, followed by BT up to a total dose of 15 Gy. S was performed 6-8 weeks thereafter. Seventeen pts (group II), FIGO IA2 (1), IB1 (14), IIB (2), were treated by BT alone with a total dose of 60 Gy and S after 6-8 weeks. All pts had a MRI examination after BT with a moulded applicator in situ for exact delineation of GTV, CTV and critical organs and a 3D dosimetry directly from MRI data.

Results: In group I (EBT + BT + S), the histopathological findings showed complete tumour sterilization (CR) in 56% of pts. Residual disease (RD) was found in 43%. Dosimetric data showed in pts with CR a larger mean treated volume (213 vs. 166 cm(3)) and a better mean coverage of the GTV and the CTV by the reference isodose (99 and 91%) as in pts with RD (85 and 77%). In group II (BT + S), CR was found in 52%, RD in 41%. Dosimetric data showed a larger mean treated volume (154 vs. 109 cm(3)) for pts with RD and a mean coverage of the GTV and the CTV by the reference isodose of 97 and 84% vs. 89 and 80% for pts with CR.

Conclusions: An incomplete coverage of the GTV and/or the CTV by the reference isodose is an important risk factor for RD at the time of surgery. Furthermore, for pts who received BT alone, tumour size seemed to be a limiting factor for an accurate coverage of the CTV by the reference isodose.