Autologous fat as a rectal-prostate spacer for prostate brachytherapy: Results at 6 months.

Purpose: Implanted rectal spacers (IRS) have been developed to increase the distance between the prostate and the rectum, thus optimizing dose escalation. Cost is a disadvantage and there are still uncertainties as to their durability. We have developed an autologous fat transfer (AFT) technique to use as an IRS. We aim to present the feasibility and durability at 6 months of AFT placed immediately after the implant of the seeds in low-dose-rate brachytherapy (BT).

Methods And Materials: Thirty-five patients underwent AFT (12 were treated with primary BT, 7 with a combined primary treatment of external beam radiotherapy + BT, 16 with salvage BT). The isodose used for primary BT was 14400 cGy, 11,000 cGy after 4600 cGy of external beam radiotherapy in the combined group, and 14400 cGy for the salvage group. Patients underwent a CT scan at 1, 3, and 6 months to measure the distance between the rectum and the prostate.

Results: An average of 32.7 cc (20-40) of fat was transferred successfully in 100% of cases. The mean distance to the rectum at the level of the base, middle, and apex at 1 and 6 months were 11.2, 9.7, and 7.6 mm; 8.3, 8.1, and 5.9 mm, respectively. No rectal toxicity or major complications were reported.

Conclusions: The use of fat as an IRS seems to be a valid alternative to reduce rectal toxicity after BT, achieving equivalent distances to synthetic IRS. It is feasible, safe, and the loss of distance at 6 months is small. Cost is lower than other alternatives.