A Prospective Single-Arm Study of Daily Online Adaptive Radiation Therapy for Cervical Cancer with Reduced Planning Target Volume Margin: Acute Toxicity and Dosimetric Outcomes.

PURPOSE: To evaluate acute toxicity and dosimetric outcomes in cervical cancer treated with daily iterative cone beam computed tomography (iCBCT) guided online adaptive radiation therapy (oART) using reduced planning target volume (PTV) margin.

METHODS AND MATERIALS: From February 2023 to November 2023, 27 patients with stages I to III cervical cancer were prospectively enrolled in this study. All patients received daily iCBCT guided oART (prescribed 50.4 Gy in 28 fractions) with concurrent weekly chemotherapy followed by brachytherapy. A uniform 10-mm margin was used to cover more variable uterus (PTV-U), and 5-mm margin was used for other PTV. The dosimetric results for each oART fraction were recorded. Both clinician- and patient-reported acute toxicities were assessed before treatment, weekly during treatment, 1 month and 3 months after treatment.

RESULTS

The average total treatment time was 22 minutes and 54 seconds, and the adapted plan was selected for all fractions. The adapted plans showed superior coverage for the target volume and dosimetric improvement of organs at risk compared with the scheduled plan. Overall, no patient had grade ≥ 4 acute toxicities. Grades 1, 2, and 3 acute gastrointestinal toxicity were 26%, 19%, and 4%, respectively, among which diarrhea was the most common. Only grade 1 acute genitourinary toxicity was observed in 2 cases (7%). The low incidence of acute toxicity was supported by patient-reported outcome data, which showed significant decreases in mean standard scores on function subscales and significant increases on symptom subscales/items following the initiation of oART. Most of these scales returned to baseline average scores by the 1-month follow-up.

CONCLUSIONS

This prospective study of daily oART in patients with cervical cancer observed dosimetric benefits and a low incidence of acute toxicity, both in clinician- and patient-reported outcome measurements.