# Outcomes of pelvic and para-aortic stereotactic reirradiation for gynaecological cancer recurrence

## TL;DR

Stereotactic reirradiation is an effective and safe treatment for gynaecological cancer recurrence in the pelvis or para-aortic region.

## Contribution

Demonstrates the efficacy and safety of SBRT reirradiation for gynaecological cancer recurrence in previously irradiated areas.

## Key findings

- Median progression-free survival of 14 months following SBRT reirradiation.
- SBRT reirradiation was well tolerated with minimal acute and late toxicity.
- Median overall survival of 42.9 months following treatment.

## Abstract

•Stereotactic reirradiation of pelvic oligometastatic disease is effective.•Median PFS of 14 months following pelvic or para-aortic SBRT reirradiation.•Benefits of SBRT reirradiation seen in both cervix and uterine cancer patients.•Acute and late radiation toxicity is minimal post SBRT reirradiation.

Stereotactic reirradiation of pelvic oligometastatic disease is effective.

Median PFS of 14 months following pelvic or para-aortic SBRT reirradiation.

Benefits of SBRT reirradiation seen in both cervix and uterine cancer patients.

Acute and late radiation toxicity is minimal post SBRT reirradiation.

Recurrence of gynaecological cancer in the pelvis is associated with significant morbidity and can be challenging to treat, particularly when arising in a previously irradiated site. For cases of oligometastatic relapse a targeted approach is preferable, avoiding the need for systemic therapy. Type 1 reirradiation using highly conformal techniques such as stereotactic radiotherapy (SBRT) is increasingly used, aiming for disease ablation at the site of relapse. We present an analysis of our institutional experience of using SBRT for gynaecological cancer reirradiation to identify efficacy, toxicity and other factors for appropriate case selection.

Patients treated with pelvic or para-aortic SBRT reirradiation at our institution for histologically proven gynaecological malignancies between July 2012 and January 2021 were identified from local records. Indications for treatment included soft tissue and nodal recurrences and cases of positive margin following surgery. Data were collected on survival, failure patterns, demographics, planning and dosimetry.

73 patients were identified who had undergone 81 courses of pelvic or para-aortic reirradiation using SBRT. Median prescribed dose was 30 Gy in 5 fractions. Following SBRT reirradiation, median overall survival was 42.9 months (95 % confidence interval, CI 36.0 to 68.9 months), median progression-free survival was 14.0 months (95 % CI 9.2 to 24.3 months). Median time to local failure of the treated lesion following SBRT reirradiation was 35.2 months (95 % CI 24.3 to not reached). SBRT reirradiation was well tolerated with acute grade 3 toxicity reported in two patients. Late grade 3 toxicity was documented in two patients, both occurring over 2 years following treatment.

In selected patients with oligometastatic pelvic or para-aortic relapse of gynaecological cancer following previous pelvic radiotherapy, SBRT reirradiation is an effective and safe treatment modality. SBRT reirradiation can provide durable local control and delay time to further treatment by more than 12 months.