Title: Space Matters - Increased Spacing using Balloon Leads to Superior Outcomes in Prostate Radiotherapy
Paulo S. Costa, Graça Fonseca, Adelina Costa, Cármen Calçada, João Conde, Carlos Fardilha, Julieta Gonçalves, Joana Vale, Fernanda Ponte, Guilherme Campos, Paula Genésio, Fátima Rodrigues, Raquel Oliveira, Benjamin W. Corn
To evaluate the impact of separation distance on dose distribution and treatment related toxicity outcomes among prostate cancer patients treated by IMRT
Materials and Methods:
From January 2015 to July 2017, 70 patients were treated for prostate cancer at our institution by IMRT. Of these, 43 underwent BioProtect® balloon spacer implantation. The remaining 27 patients were considered as a control group.
Both groups were monitored for quality of Life (QoL) and treatment related toxicities.
To facilitate dosimetric comparison, additional CT scans were performed pre-balloon implantation.
Separation was measured between the anterior rectal wall and the prostate capsule in the planning CT scan.
Dose reduction was calculated by determining the percentage differences in cubic centimetres (cc) for dose volume histograms of the V50%, V70% at the prescribed dose level. Maximum and average doses to the rectum were also evaluated.
Toxicity was registered using the CTCAE v.4 index and QoL was measured using the EPIC scoring index questionnaire for bowel habits and urinary function at the outset and at the end of the treatment course. Comparison was made to the control group treated in the same hospital with the same treatment schedule.
An average separation of 1,87cm between prostate and rectum was obtained.
A significant dose reduction for both V50% and V70% parameters with pvalue<0,0001 was obtained as well as a reduction of the maximum and average dose given to the rectum that correlated significantly comparing the dosimetric parameters of the pre and post balloon implant (pvalue<0,0001).
No balloon placement related toxicities were observed.
Balloon implant group had no significant reduction in the bowel habits EPIC QoL questionnaire, while a significant reduction in the same parameters was observed for the control group, pvalue<0,0005. Comparing both groups (control vs implant) prior to treatment for bowel habits and urinary function EPIC QoL scoring index no significant differences were found.
For the implantation group, grade 1 and 2 rectal toxicity was found in 9 and 2 patients respectively.
No grade 3 toxicities were reported for urinary and bowel symptoms.
Increased separation with a balloon spacer between rectum and prostate appears to be a safe and effective tool allowing for lower rates of radiation related toxicities, and better EPIC QoL scoring indexes for bowel habits.
The BioProtect® balloon spacer has advantageous characteristics compared with other spacing solutions, in particular the amount of spacing achieved and the related homogeneity.
This spacer system presents the possibility of adjustable placement (including deflation and repositioning) during the procedure, avoiding any asymmetric deployment, allowing for optimal positioning of the balloon.
Our study shows a significant improvement in both (V50% and V70%) dosimetric parameters to the rectum. The EPIC QoL scoring index, with regards to bowel habits, was favourably influenced by the balloon device.