High-dose-rate brachytherapy boost for elderly patients with intermediate to high-risk prostate cancer: 5-year clinical outcome of the PROSTAGE cohort.

To analyze the oncological outcome in elderly (>70 years) prostate cancer after high-dose rate brachytherapy (HDB) boost.

In this retrospective study, patients with intermediate (IR) and high-risk (HR) prostate cancer underwent external beam radiation therapy (EBRT) followed by HDB boost with/without androgen deprivation therapy (ADT). The impact of age (≤70y vs. > 70y) was investigated. Oncological outcome focused on biochemical relapse-free survival (bRFS), cause-specific (CSS) and overall survival (OS). Late genito-urinary (GU) and gastro-intestinal (GI) toxicities were investigated.

From 07/08 to 01/22, 518 pts received a HDB boost, and 380 were analyzed (≤70y:177pts [46.6%] vs. > 70y:203pts [53.4%]). Regarding NCCN classification, 98 pts (≤70y: 53pts; >70y: 45pts; p = 0.107) and 282 pts (≤70y: 124pts; >70y: 158pts; p = NS) were IR and HR pts respectively. Median EBRT dose was 46 Gy [37.5-46] in 23 fractions [14-25]. HDB boost delivered a single fraction of 14/15 Gy (79%). ADT was used in 302 pts (≤70y: 130pts; >70y: 172pts; p = 0.01). With MFU of 72.6 months [67-83] for the whole cohort, 5-y bRFS, 5-y CSS and 5-y OS were 88% [85-92], 99% [97-100] and 94% [92-97] respectively; there was no statistical difference between the two age groups except for 5-y CSS (p = 0.05). Late GU and GI toxicity rates were 32.4% (G ≥ 3 7.3%) and 10.1% (no G3) respectively.

For IR and HR prostate cancers, HDB boost leads to high rates of disease control with few late G ≥ 3 GU/GI toxicities. For elderly pts, HDB boost remains warranted mainly in HR pts, while competing comorbidity factors influence OS.

Clinical and translational radiation oncology. 2022 May 21*** epublish ***

Delphine Marotte, Jocelyn Gal, Renaud Schiappa, Mathieu Gautier, Rabia Boulahssass, Marie-Eve Chand-Fouche, Jean-Michel Hannoun-Levi

Department of Radiation Oncology, Antoine Lacassagne Cancer Center, University of Côte d'Azur, 33 avenue Valombrose, 06189 Nice Cedex 2, Nice, France., Department of Statistics, Antoine Lacassagne Cancer Center, University of Côte d'Azur, Nice, France., Geriatric Coordination Unit for Geriatric Oncology (UCOG) PACA Est, CHU de NICE, University of Cote d'Azur, Oncoage, Nice, France.