Patterns of Failure in Patients Receiving MRI-based Intracavitary HDR Brachytherapy Using Special Optimization Technique for Cervical Cancer

Abstract:Purpose/Objective: Both MRI and 3-D treatment planning system enabled us to detect tumor extent and to optimize and individualize the treatment volume using intracavitary HDR brachytherapy. This study is to analyze the patterns of locoergional failure in patients with cervical cancer treated with MRI-based intracavitary HDR brachytherapy using special optimization technique. Materials/Methods: Between January 1995 and December 1999, 47 patients with histologically confirmed squamous cell carcinoma of the uterine cervix (FIGO Stage Ib: 8, stage II b: 20, stage IIIb: 19) were treated with external irradiation and MRI-based intracavitary HDR brachytherapy. Average age of the patients was 62.4 years (range: 40-85 years). Median follow-up duration was 54 months (range: 2-98 months). All patients were treated with 30Gy whole pelvic irradiation followed by 20Gy boost to parametrium. Both CT and MRI were performed at the first and third time of intracavitary brachytherapy under applicator insertion. The GTV was defined as not a pear-shaped volume in 'Manchester system' but a high signal intensity region obtained from MRI. The PTV was defined as a volume, which include 1cm margin in cranio-caudal directions. We delivered 6Gy/fraction to the PTV, one fraction /week, to a total dose of 24Gy. We evaluated the failure pattern of this treatment technique, the 5 year over all survival rate, RFS rates, point A dose, maximum rectal and bladder dose, late morbidity of the rectum and bladder (RTOG/EORTC). Results: Seven patients have died of their cervical cancer and one died of intercurrent disease without evidence of recurrence. Eight patients relapsed. The median time to relapse was 14 months from the start of treatment (range; 2-36 months). Five local failures (2 persistent, 3 recurrent disease) and 3 distant metastases were found. Two persistent cases were uncontrolled at the end of radiation therapy because of the under dose regions in the PTV (geometrical miss). Both of them were treated with surgery and are alive. Of these 3 recurrent cases, 2 were in body of the uterus (outside PTV) and another one in uterine cervix. Retrospective analysis of this study revealed that no local recurrence was occurred in the cases with normal cervix structure between cervical tumor and uterine body. Three distant relapse (paraaortic LN metastases) were found following their pelvic LN failure. The 5 year over all survival and RFS rates according to stage were as follows; stage Ib: 100%, 87.4%, stage IIb: 83.1%, 94.1%, stage IIIb: 67%, 65.7%, respectively. Average point A dose was 501cGy (ranged: 119-710cGy). Average maximum dose of the bladder and rectum were 597cGy (ranged: 261-1101cGy) and 549cGy (ranged: 237-934cGy), respectively. Grade 1 late morbidity of bladder was observed in 2/49. Grade 1and 2 late morbidity of rectum were observed in 7/49 and 1/49, respectively. No cases were observed greater than Grade 3 morbidity at 5 years. Conclusions: We have shown that the special brachytherapy technique with a target delineation using MR images for patients with cervical cancer is feasible and less toxic. >From this study, it would be better to optimize the dose distribution to the PTV without covering the uterine body if the tumor exists only within the cervix. This technique might reduced a high dose exposure to rectum and bladder and also reduce high-grade morbidities. Questions about this event email: khatano@chiba-cc.jp

E15-498

Patterns of Failure in Patients Receiving MRI-based Intracavitary HDR Brachytherapy Using Special Optimization Technique for Cervical Cancer