Literature analysis of high dose rate brachytherapy fractionation schedules in the treatment of cervical cancer: Is there an optimal fractionation schedule?

Purpose: A literature review and analysis was performed to determine whethe r or not efficacious high dose rate (HDR) brachytherapy fractionation sched ules exist for the treatment of cervical cancer. Methods and Materials: English language publications from peer reviewed jou rnals were assessed to calculate the total contribution of dose to Point A from both the external and intracavitary portions of radiation for each sta ge of cervical cancer. Using the linear quadratic formula, the biologically effective dose to the tumor, using an alpha/beta = 10, was calculated to P oint A (Gy10) in order to determine a dose response relationship for local control and survival. Significant complications were assessed by calculatin g the dose to the late-responding tissues at Point A using an alpha/beta = 3 (Gy3) as a surrogate for normal tissue tolerance, since few publications list the actual bladder and rectal doses. Results: For all stages combined, the median external beam fractionation sc hedule to Point A was 10 Gy in 20 fractions, while the median HDR fractiona tion schedule was 28 Gy in 4 fractions. For stages IB, IIB, and IIIB the me dian biologically effective dose to Point A (Gy10) was 96, 96 and 100 Gy10s , respectively. No correlation was identified between Point A BED (Gy10s) t o either survival or pelvic control. A dose response relationship could als o not be identified when correlating Point A Gy3s to complications. Conclusion: A dose response relationship could not be identified for either tumor control nor late tissue complications. These findings do not necessa rily question the validity of the linear quadratic model, as much as they q uestion the quality of the current HDR brachytherapy literature as it is cu rrently presented and reported. Most of the HDR publications report inadequ ate details of the dose fractionation schedules. Only a minority of publica tions report significant complications using the actuarial method. In the f uture, all HDR publications for the treatment of cervical cancer should pro vide accurate fractionation details for each stage of disease, while report ing actuarial complication rates. The optimal fractionation schedule for tr eating cervical cancer using HDR brachytherapy is still unknown, and presen tly can be based only on single institutions with significant experience. ( C) 1999 Elsevier Science Inc.