RESUMO
Introduction This study aimed to measure cervical regression during external beam radiation therapy (EBRT) and optimize the scheduling of brachytherapy concurrently with EBRT. Methods Fifty consecutive patients with carcinoma of the cervix stage IIA to IIIB received concurrent chemoradiotherapy with weekly Cisplatin 40 mg/m2. Cervical regression was evaluated using serial CT scans obtained before and during concurrent chemoradiotherapy (on the third, fourth, and fifth weeks). High dose rate brachytherapy was introduced after 30Gy of EBRT. A total of 25.5Gy in three fractions were delivered during the third, fourth, and fifth weeks of EBRT. Cervical volumes were recorded from the CT scan for cervical regression. Results The mean cervical volume at baseline (i.e., before the start of treatment) was 85.53 cubic centimetres (cc). The mean cervical volumes at the end of the third, fourth, and fifth week were 28.95cc, 24.92cc, and 21.80cc, respectively. The mean cervical regression from baseline to the end of the third, fourth, and fifth week was 60%, 65%, and 69%, respectively. The time for 50% cervical regression was calculated to be 18 days and occurred around 27Gy of EBRT. Conclusion More than 50% of cervical regressions occur at the end of the third week (i.e., after delivery of 30Gy of EBRT), so it is optimal to introduce brachytherapy at the end of the third week. A conventional point-based plan can cover the high-risk clinical target volume (HRCTV) if the volume is <25cc, but an HRCTV >25cc may be well covered with optimization or a combination of intracavitary and interstitial brachytherapy.
