MRI-guided HDR brachytherapy or integrated VMAT boost for tumour-targeted dose escalation in localised prostate cancer: long-term results of the TARGET study.

Purpose

To evaluate local control of the gross tumour volume in localised prostate cancer following focal dose escalation delivered by integrated boost volumetric modulated arc therapy (IB-VMAT) or high-dose-rate (HDR) brachytherapy.

Materials And Methods

Patients with localised prostate cancer and an intraprostatic lesion identified on multiparametric magnetic resonance imaging (mpMRI) were included in a prospective, non-randomised phase II study. Eighty patients received VMAT to the prostate 76 Gy/38 fractions. Boost strategy involved an IB of 95 Gy/38 fractions (IB-VMAT) or a single fraction of 10 Gy (HDR-VMAT). Three patients received 6 months androgen deprivation therapy. The primary endpoint was 3-year local control (LC) assessed by MRI or MRI-guided biopsy. Secondary outcomes included biochemical failure-free survival (bFFS), toxicity and health-related quality of life (HRQoL), assessed using CTCAE v.4.0, the American Urological Association Symptom Score and EPIC.

Results

Median follow-up was 4.8 years (IQR, 4.0-8.0). Sixty-six patients underwent a 3-year MRI or MRI-guided biopsy; one patient demonstrated recurrence within the boost volume. Four patients demonstrated intraprostatic failure outside the boost volume and three patients developed regional/distant metastases. Eight patients experienced biochemical failure (4 IB-VMAT; 4 HDR-VMAT). Overall, 5-year bFFS was 86.9% (95% CI, 79.1-95.5). No substantial differences in late toxicities and HRQoL were observed between cohorts.

Conclusion

Intraprostatic tumour-targeted dose escalation using IB-VMAT or HDR-VMAT provided high rates of LC and bFFS with limited adverse impact in late toxicity and HRQoL. Randomised studies are needed to further define the merits and differences between the two techniques.