Gynaecological reirradiation with image-guided radiotherapy: Tumour Control Probability and Normal Tissue Complication Probability in pre-immunotherapy era.

Background and purpose: Management of recurrent gynaecological cancers after previous pelvic radiation is challenging. This institutional cohort describes clinical outcomes with image-guided radiotherapy techniques.

Materials and methods: From 2020 to 2023, patients with recurrent or second primary gynaecological malignancies previously treated with radiotherapy were included. Reirradiation was delivered using image-guided volumetric arc therapy (IG-VMAT), stereotactic body radiotherapy (SBRT), and/or image-guided brachytherapy (IGBT) as clinically appropriate. Infield control, progression-free survival (PFS), and overall survival (OS) were estimated using the Kaplan-Meier method. Prognostic factors for infield control were assessed with uni- and multivariate analyses. Adverse events were reported (CTCAE version 5.0). The dose-response effect for tumour control and late effects were estimated.

Results: Seventy patients underwent reirradiation. Of these 62 (88.5 %), 6 (8.5 %), and 2 (2.8 %) had cervical cancer, endometrial cancer, and vulvovaginal cancer, respectively. The majority of patients had squamous cell histology (81.4 %). Fifty-nine patients (84.2 %) were treated for local and/ or nodal recurrence, and 11 patients were treated (15.8 %) for second primary cancer. The median reirradiation dose was 50 Gy (IQR 42.2-64.2 Gy). In this cohort, 34/70 (48.6 %) patients received systemic chemotherapy, and no Bevacizumab or Immunotherapy. With a median follow-up of 37 months, the 3-year infield control, PFS, and OS were 63.5 %, 62.4 %, and 68 %, respectively. Reirradiation dose ≥50 Gy and disease-free interval ≥24 months were independently associated with improved infield control (p = 0.04, 0.004). Grade ≥3 gastrointestinal/genitourinary toxicity occurred in 18.5 % patients. Cumulative EQD2 ≥130 Gy₁₀ predicted for grade ≥3 toxicity (p = 0.008).

Conclusions: Image-guided radiotherapy techniques for reirradiation achieve excellent local control with acceptable toxicity in patients with recurrent gynaecological cancers.