Endorectal balloon facilitated dose-escalation salvage radiation therapy without compromising rectal dose constraints for a solitary macroscopic recurrence in prostate bed after prostatectomy.

Early salvage radiation therapy (sRT) is a potentially curative treatment for patients with recurrent prostate cancer (PC) after radical prostatectomy (RP). Total dose of 64 to 66 Gy in 32 to 33 fractions to prostate bed (PB) is commonly used in sRT for biochemical recurrence (BCR). In the event of macroscopic local recurrence (MLR), additional boost dose to MLR (total of greater than 74 Gy in 37 fractions) have shown an improved tumor control. Because MLR in PB often abuts the rectum, however, dose-escalation sRT (DE-sRT) to MLR can be limited due to exceeding rectal dose constraints resulting in suboptimal tumor control. Endorectal balloon (ERB) during definitive RT for localized intact PC has shown decreased rectal dose by pushing the posterior and lateral rectal wall away from prostate and high-dose region resulting in reduced rectal toxicity. Applying ERB in patients with previous RP can also create similar favorable anatomical changes in rectum which may allow DE-sRT to MLR in PB while limiting rectal dose. In this report, we describe our experiences of successful DE-sRT (78 Gy in 39 fractions to MLR in PB) with the novel use of EBR resulting in complete resolution of MLR in PB and undetectable PSA without rectal complications.