ESTRO 2024 - Abstract Book

S423

Brachytherapy - Urology

ESTRO 2024

The majority of patients had intermediate risk disease according to NCCN criteria (61.6% in HDR-SBRT group vs 54.8% in SBRT alone). Notably, the exclusive SBRT arm had a higher proportion of low-risk patients (34.4% vs 11.6%), whereas the combination arm of HRD-SBRT had a higher proportion of high-risk patients (26.1% vs 10.7%).

The median % of positive cores was 36% in HDR-SBRT group and 31% in SBRT alone group.

Short-term ADT (up to 6 months) was administered to 36.3% of patients in the HDR group and 24.7% in the exclusive SBRT group, whereas 37% and 14% respectively received long-term ADT (6-36 months). The remaining patients did not received ADT. The cumulative incidence of acute G2 GU toxicity was significantly lower in the HDR-SBRT vs SBRT arm 13.7% vs 35.5% (p=0,00) . The most common acute GU symptom was dysuria. One patient in the HDR-SBRT arm experienced grade 3 acute GU toxicity consisting in dysuria. No acute grade 3 events were recorded in the SBRT group. The majority of patients (67% in HDR-SBRT and 65% in SBRT arm) did not experience late GU toxicity. Similar rates of grade 2 late GU toxicity were observed in both arms, 4.8% vs 7.5% respectively. The most common late GU symptom was nocturia. Grade 3 late GU toxicity was documented in 2 patients (both HDR-SBRT arm); one of them presenting obstructive symptoms, and the other with intense irritative symptoms.

Acute grade 2 GI toxicity was significantly lower in HDR-SBRT group 30% vs 70% (p=0.02). The most common acute GI event was proctitis. No differences were observed between groups in terms of Late GI toxicity.

The median PSA value at 18 months was 0.4 ng/mL for the HDR-SBRT group and 0.6 ng/mL for the SBRT group. PSA kinetics after treatment in patients who did not received ADT were similar between groups (Figure 1).

No significant decline in patient QoL (EPIC, EORTC) was observed in any of the domains studied (urinary, bowel, sexual and hormonal).

Three percent of the total cohort (7 patients, 5 of them of the HDR-SBRT arm) experienced biochemical failure, 4 of them with metastases (2 of each group) and the other 3 with regional disease (all from HDR-SBRT arm).

Conclusion:

Both treatment modalities, HDR-SBRT and SBRT, demonstrate positive outcomes concerning toxicity, quality of life and disease control. Nevertheless, exclusive SBRT seems to be associated with higher acute G2 GU and GI toxicity.

Keywords: HDR-Brachytherapy, SBRT, prostate cancer

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