Prostate Brachytherapy Boost in the Elderly: Results of a Comparative Study

Abstract

<h3>Purpose/Objective(s)</h3> To analyze the oncological outcome and toxicity profile in elderly (> 70 years) prostate cancer after high-dose rate brachytherapy (HDB) boost. <h3>Materials/Methods</h3> In this retrospective observational single institution study (Health-data-hub N°F20201008194116), patients with intermediate (IR) and high-risk (HR) prostate cancer underwent external beam radiation therapy (EBRT) followed by HDB boost with or without androgen deprivation therapy (ADT). The impact of patient age (≤ 70 y vs. > 70 y) was investigated. Oncological outcome focused on biochemical (BRFS), local (LRFS), regional (RRFS) and metastatic relapse-free survival (MRFS) as well as Disease-free (DFS), Cause-specific (CSS) and overall survival (OS). Late genito-urinary (GU) and gastro-intestinal (GI) toxicities were investigated. <h3>Results</h3> From 02/09 to 12/21, 519 pts received a HDB boost. Among them, 387 were analyzed (≤70y: 180 pts [47%] vs. >70y: 207 pts [53%]). Regarding NCCN classification, 98 pts (≤70y: 53 pts; >70y: 45 pts; p = NS) and 289 pts (≤70y: 127 pts; >70y: 162 pts; p = NS) were IR and HR pts respectively. Intensity modulated RT was used in 241 pts (62.6%) with pelvic irradiation in 336 pts (86.2%) for a median dose of 45.5 Gy [35 – 57.5] in 23 fractions [15 - 25]. HDB boost was performed under general/spinal anesthesia delivering a single fraction of 14 or 15 Gy for 307 pts (79.3%). ADT was used in 309 pts (≤70y: 133 pts; >70y: 176 pts; p = 0.009) for a median time of 17.1 months [3 - 41] (IR: 6 months; HR: 18.8 months). With a median follow-up (MFU) of 72.3 months [64.6 – 81.1] for the whole cohort, 5-y BRFS, 5-y LRFS, 5-y RRFS and 5-y MRFS were 88% [84 - 92], 97% [95 - 99], 99% [98 - 1], 95% [93 - 98] respectively with 5-y DFS, 5-y CSS and 5-y OS of 84% [80-88], 99% [97-100] and 94% [92 - 97]. With the same MFU of 60 months in both age groups, oncological outcome was not statically different except for the 5-y CSS (≤70y: 97% [94 - 100] vs. >70y: 100%; p=0.05). Late GU toxicity was observed in 124 pts (32.1%) with 9 G3 pts (7.2%). Late GI toxicity was observed in 41 pts (10.2%) with no G3. However, in a subgroup analysis comparing 70y< pts ≤80y vs. >80y pts, a significant difference was noticed in terms of late GU toxicity (29.7% vs. 61.9%; p = 0.006). <h3>Conclusion</h3> For IR and HR prostate cancers, HDB boost leads to high rates of disease control with less than 3% of late G3 GU/GI toxicities. For elderly pts (>70y), HDB boost remains warranted in order to achieve optimal oncological outcome mainly in HR pts, although competing comorbidity factors will significantly impact the OS. However, HDB boost should be carefully discussed in the super senior pts (> 80 y). Due to the increase in life expectancy, the management of prostate cancer in the elderly is a real challenge for patients, clinicians, health care providers and payers. Except for unfit men, elderly patients remain candidates for optimal curative treatment (i.e., regardless of age) after oncogeriatric assessment.