Radiotherapy Boost for the Dominant Intraprostatic Cancer Lesion—A Systematic Review and Meta-Analysis

External beam radiotherapy (EBRT) for prostate cancer can be performed with a high dose of 86 Gy; however, one-tenth or more of the patients will develop recurrence. Prostate cancer is mainly multifocal, but a dominant intraprostatic lesion (DIL) is often the site of local recurrence after EBRT. We undertook a systematic review and meta-analysis to clarify whether functional imaging might identify the DIL and whether a RT boost to the DIL might be increased to an ultrahigh dose level of ≥ 90 Gy without increased toxicity. Of 62 selected studies, 13 reported the size of the DIL. The mean of the median DIL volumes was 2.4 cm3 (95% confidence interval, 0.9-4.4 cm3). Eighteen diagnostic studies with 1205 patients evaluated the diagnostic accuracy using multiparametric magnetic resonance imaging for intraprostatic cancer lesions. Evaluating 14,654 prostate segments, the diagnostic accuracy was 77%. Eleven therapeutic studies with 988 patients reported a RT boost for the DIL. The summary boost dose for the DIL was a mean of 89 Gy in 5 studies using intensity modulated RT (calculated as the equivalent dose in 2-Gy fractions) and a mean of 141 Gy in 4 studies using a combination of EBRT and brachytherapy (P = .018, t test). In 1 therapeutic study, 239 patients had a 98% 10-year disease-free survival rate. Many of our therapeutic studies used a boost dose to the DIL of > 90 Gy. The reported boost for DIL is effective and safe.