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

Abstract

IntroductionThis 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. MethodsThe 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. ResultsResults 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. ConclusionA 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.