PPP06 Presentation Time: 11:15 AM

Purpose/Objective(s)

To describe long-term outcomes of a useful technique to decrease rectal dose during HDR prostate brachytherapy given as a boost to EBRT or as monotherapy. Prostate brachytherapy has evolved in recent years. It has become popular to use HDR and 3D planning, using CT and/or MRI, which has helped improve treatment capabilities to dose scaling, due to the real visualization allows to optimize the therapeutic index, escalate dose into the tumor, and protect OARs. The long-term outcomes analysis of a multicentric Latin American experience from Peru and Colombia with patients treated with this premise, using blood as OAR spacer, presented as an alternative to this procedure in developing countries with limited resources.

Materials/Methods

from 2017 - 2020, 300 patients underwent HDR prostate brachytherapy in 3 institutions in Latin America, the first experience in Peru and Colombia. Under spinal anesthesia and sedation, approx. 16 mL of blood was extracted from the patient via antecubital venipuncture and mixed with 4 ml of iodine venous contrast as the technique firstly described in 2008 by Morancy from Boston for prostate LDR brachytherapy. The perineum was prepared for a sterile procedure. Under ultrasound guidance, an 18G spinal needle was placed to open the space below the Denonvilliers fascia for hydro-dissection, after that, the volume of blood was then instilled within the peri-rectal space on each side, as the needle was withdrawn, using the sagittal ultrasound image for guidance as the technique described by Hatiboglu in 2012 in Heidelberg. After the creation of the blood patch, a standard brachytherapy needle insertion to the prostate is performed under US guidance, followed by CT Simulation, and then MR fusion is performed for treatment planning. Following completion of the procedure, the change in the anterior peri‐rectal space was determined by comparing the diagnostic CT‐ and post‐patch contours. The dose plan was held constant by superimposing the post‐patch plan over the diagnostic CT contours. Needle positions were shifted posteriorly based on the change in peri‐rectal space. Prescribed dose to PTV in monotherapy 2 fractions of 13.5 Gy and as Boost to EBRT 15 Gy.

Results

A blood patch was successfully applied in all 300 patients. The blood patch thickness will decrease by 50% in 10 to 15 days after the application. All the rectal dose parameters above the V20 - V80 were significantly improved by the blood patch, also the Dmax and it was correlated with the homogeneity of the blood patch application, V5-V10 weren't significant because these isodoses are 5 to 6 cm far from the target. The average pre-rectal space obtained was 0.83 cm. The diametric potential advantages of the blood patch are that the mean dose to 0.1 cc of the rectum was limited to 57.4% and the mean dose to 2 cc of the rectum being 40%, also parameters such as D90 and V100 were significantly improved, with regard clinical outcomes after 36 months average follow up overall all late G3 toxicities 10% and urethral strictures 7% in boost cohort, and overall all late G3 toxicities 3% and urethral strictures 1% in Monotherapy cohort.

Conclusions

The use of a pre-rectal Blood patch REDUCE the integral radiation dose to the rectum and may help to decrease the amount of possible acute and late rectal toxicities due to prostate HDR brachytherapy procedure, letting us do a safe dose escalation treatment to improve outcomes. This technique is feasible and could be particularly beneficial in patients with minimal peri-rectal fat. This technique appears to be a cost-effective way to improve outcomes in developing countries with limited resources.