Dosimetric comparison of rectal-sparing capabilities of rectal balloon vs injectable spacer gel in stereotactic body radiation therapy for prostate cancer: lessons learned from prospective trials
- Department of Radiation Oncology, Simmons Comprehensive Cancer Center at the University of Texas Southwestern Medical Center, Dallas, TX (United States)
- Department of Radiation Urology, Simmons Comprehensive Cancer Center at the University of Texas Southwestern Medical Center, Dallas, TX (United States)
- Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY (United States)
This study aimed to compare the rectal-sparing capabilities of rectal balloons vs absorbable injectable spacer gel in stereotactic body radiation therapy (SBRT) for prostate cancer. Patient samples included in this analysis were obtained from 2 multi-institutional prospective trials of SBRT for prostate cancer using a rectal balloon (n = 36 patients) and injectable spacer gel (n = 36). Treatment prescription dose was 45 Gy in 5 fractions in 42 patients; for equal comparison, the remaining 30 patients were rescaled to 45 Gy from 47.5 Gy prescription (n = 6) and 50 Gy prescription (n = 24). The median prostate volumes and body mass index in the 2 patient samples were not statistically significantly different (p = 0.67 and 0.45, respectively), supporting anatomic similarity between cohorts. The injectable spacer gel achieved dosimetric superiority over the rectal balloon with respect to the maximum dose to the rectum (42.3 vs 46.2 Gy, p vs 35.1 Gy, p Gy), V40{sub Gy}, and V30{sub Gy} (0.3 vs 1.7 cc, 1 vs 5.4 cc, and 4.1 vs 9.6 cc, respectively; p Gy of the rectum or the dose to 50% of the rectal circumference (p = 0.29 and 0.06, respectively). The V18.3{sub Gy} of the bladder was significantly larger with the rectal balloon (19.9 vs 14.5 cc, p = 0.003). In this analysis of patients enrolled on 2 consecutive multi-institutional prospective trials of SBRT for prostate cancer, the injectable spacer gel outperformed the rectal balloon in the majority of the examined and relevant dosimetric rectal-sparing parameters. The rectal balloon did not outperform the injectable spacer gel in any measured rectal dose parameter.
- OSTI ID:
- 22837711
- Journal Information:
- Medical Dosimetry, Journal Name: Medical Dosimetry Journal Issue: 4 Vol. 42; ISSN 0958-3947
- Country of Publication:
- United States
- Language:
- English
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