Redefining the role of pulsed-dose-rate brachytherapy in cervical cancer treatment using a preplanned approach.

ABSTRACT

INTRODUCTION: This study aims to determine predictive factors for cervical cancer patients who would benefit more from high-dose-rate (HDR) or pulsed-dose-rate (PDR) brachytherapy. METHODS: The sample included 50 patients treated with brachytherapy following external radiochemotherapy. PDR plans were compared to HDR preplans, with a focus on patients who may benefit from PDR using preplan metrics and clinical variables. The expected clinical effect was quantified using a tumor control probability model. RESULTS: Results showed PDR plans with 60 pulses to be optimal for achieving target clinical goals for D90CTVHR. A CTVHR volume of >67.5cc and/or D90CTVHR dose on the HDR preplan of <31.1 Gy was the strongest indicator for patient selection who would gain >3% increase in TCP with PDR. The process showed 96% accuracy, 88% sensitivity, and 98% specificity. Only 16% of patients showed a relevant benefit from PDR over HDR, with a mean D90CTVHR of 7 Gy higher and a mean TCP at 3 years of 4.8% higher for PDR. The benefit of PDR is highly influenced by the choice of alpha/beta ratio and repair halftime. CONCLUSION: A small subset of cervical cancer patients may gain from PDR over HDR. CTVHR volume and preplan D90CTVHR doses may be useful in selecting patients for PDR brachytherapy.