Model assessment of individual tumor control rate and adverse effects in comparing locally advanced cervical cancer treatment using intracavitary with and without interstitial brachytherapy

Abstract

PurposeThis study assessed the modeled probability of tumor control and organ at risk toxicities in locally advanced cervical cancer in patients treated by external beam radiation plus brachytherapy using intracavitary combined with interstitial brachytherapy (IC/IS) vs. intracavitary brachytherapy (IC) alone.Material and methodsTwenty cervical cancer patients with a mean HR-CTV volume of 47.4 cm3 and a mean width of 54 mm were planned with both IC/IS and IC brachytherapy alone. A probit model was utilized to model 3-year (3-yr) local control rate (LC), 3-yr cancer specific survival rate (CSS), and the adverse effect (AE) of the organ at risk by using a modeled data set from multiple institutions. Modeling results were used to estimate the LC, CSS, and AE of the treatments in this study.ResultsUsing the IC/IS technique, an EQD2 increase of 12.3 Gy to D90 (from 76.1 Gy to 88.3 Gy) of HR-CTV is expected to increase 3-yr LC and 3-yr CSS by 12.5%, and 11.0%, respectively. Comparing IC/IS to IC alone, the expected G2+ AE were 7.7% vs. 7.9% for the bladder, and 5.9% vs. 6.8% for the rectum.ConclusionsThe IC/IS technique improved dose coverage to the HR-CTV without significantly increasing dose to 2 cm3 of the organ at risk (OAR) surrounding it. With different regimens of EBRT combined with BT, IC/IS can be used to increase the probability of LC and CSS, or decrease the risk of AE.

Commentary: “Long-Term Outcomes and Prognostic Analysis of Computed Tomography-Guided Radioactive 125 I Seed Implantation for Locally Recurrent Rectal Cancer After External Beam Radiotherapy or Surgery”: Letter to the Editor

“…First, when they applied the Chi-square test and Fisher’s exact test to analyze factors correlated with adverse effects, they did not include the dose of the organ at risk (OAR) such as D2cc or D0.1cc of skin or mucosa. It is well known that the dose of OAR is closely related to the occurrence of radiation damage ( 2 – 4 ). Therefore, we recommend that the authors further analyze the detailed relationship between the dose of OAR and radiation damage.…”