Faculty Collaboration Database

Comparision of four different dose specification methods for high-dose-rate intracavitary radiation for treatment of cervical cancer. Int J Radiat Oncol Biol Phys 2001 Nov 15;51(4):1131-41

Date

11/13/2001

Pubmed ID

11704338

DOI

10.1016/s0360-3016(01)01771-0

Scopus ID

2-s2.0-0035889372 (requires institutional sign-in at Scopus site)   30 Citations

Abstract

PURPOSE: To compare the dose delivered to target tissues and dose-limiting structures as defined by specific dose points with high-dose-rate intracavitary brachytherapy using tandem and ring or tandem and ovoids applicators, and to provide a reasonable approach to dose optimization.

METHODS AND MATERIALS: Dosimetry was obtained using four different dose specifications: (1) 100% of the dose prescribed in a tapered fashion along the tandem and 140% at the ovoid/ring surface, (2) 100% of the dose prescribed along the tandem and 100% at the ovoid/ring surface, (3) 100% of the dose prescribed to point A without any additional applicator specification points, and (4) nonoptimized plan using relative dwell weighting to simulate classic Fletcher low-dose-rate (LDR) loading with the dose specified at point A. Point doses were recorded at A, B, and T (cervical tumor point), ICRU rectum, and ovoid/ring surface.

RESULTS: For the tandem and ovoids applicators, significant differences were found among the four different dose specification methods for point T and vaginal mucosal doses. When the dose was optimized to point A alone, the ovoid dwell weights were reduced, resulting in higher point T doses and underdosing of the vaginal mucosa. Fixed weighting based on Fletcher LDR loading specifications resulted in higher vaginal mucosa doses. For the tandem and ring applicators, significant differences were observed for vaginal mucosal doses and the ICRU rectal dose. Optimization to point A alone resulted in widely varying dosimetric distributions and vaginal mucosa doses up to 632% of the prescription dose. With nonoptimized fixed weighting, the vaginal wall dose and ICRU rectal dose were increased.

CONCLUSION: Prescribing to dose optimization points in a tapered fashion along the tandem and at the ovoid/ring surface results in a pear-shaped dose distribution resembling classic LDR systems. The other dose specification methods may result in underdosing of important target tissues or overdosing of adjacent dose-limiting structures.

Author List

Mai J, Erickson B, Rownd J, Gillin M

Authors

Beth A. Erickson MD Professor in the Radiation Oncology department at Medical College of Wisconsin
Jason Rownd MS Instructor in the Radiation Oncology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Brachytherapy
Female
Humans
Intestines
Mucous Membrane
Radiometry
Radiotherapy Dosage
Treatment Outcome
Urinary Bladder
Uterine Cervical Neoplasms
Vagina