Outcomes of Computed Tomography-Guided Image-Based Interstitial Brachytherapy for Cancer of the Cervix Using GEC-ESTRO Guidelines.

Abstract

Locally advanced cancer of the cervix is treated by concurrent chemoradiation followed by brachytherapy. Interstitial brachytherapy is used to treat large tumors with involvement of parametrium, post-hysterectomy, and narrow, conical vagina. The GYN GEC-ESTRO working group described target volume delineation and also 3D image-based planning using MRI and 3D dose-volume parameters for brachytherapy of carcinoma cervix. CT-based as compared to MR-based image-guided brachytherapy (IGBT) is much more feasible and practical because MR access is still difficult for most departments. This is a retrospective study done to assess the local control in cancer of the cervix, treated based on these guidelines and dose received by 2cm3 of the rectum as defined by the GEC-ESTRO guidelines and its correlation with long-term toxicity. Sixty-three patients of cancer of the cervix received 45Gy/25 fractions of external beam radiotherapy with concurrent weekly cisplatin followed by interstitial brachytherapy. A central tandem was inserted into the uterine cavity. The needles were inserted based on the concept of gross tumor volume (GTV), high-risk clinical target volume (HRCTV), and intermediate-risk CTV (IR CTV) as defined by the GYN GEC-ESTRO guidelines. All patients underwent CT-based planning. A dose of 6.5Gy × 4 fractions was delivered in two sessions such that the HRCTV received a total dose of 26Gy. Dose optimization was done to prevent 2cm3 of rectum from receiving > 400cGy (60% of prescribed dose) per fraction and 2cm3 of bladder from receiving 500cGy per fraction. At a median follow-up of 41.5months (range 6-106months), 74.6% (47/63) of the patients were alive, with no local, loco-regional, or distant metastasis. Loco-regional control rate was 88% (56/63). Eight percent (5/63) of the patients developed grade I proctitis which was managed conservatively. There was no grades II, III, or IV proctitis. There was no bladder or sigmoid toxicity. GEC-ESTRO guidelines can be modified for CT-based planning also with very minimal late toxicity without compromising local control.