A multi-institutional phase 2 trial of high-dose SAbR for prostate cancer using rectal spacer Journal Article
| Authors: | Folkert, M. R.; Zelefsky, M. J.; Hannan, R.; Desai, N. B.; Lotan, Y.; Laine, A. M.; Kim, D. W. N.; Neufeld, S. H.; Hornberger, B.; Kollmeier, M. A.; McBride, S.; Ahn, C.; Roehrborn, C.; Timmerman, R. D. |
| Article Title: | A multi-institutional phase 2 trial of high-dose SAbR for prostate cancer using rectal spacer |
| Abstract: | Purpose: High-dose SABR for prostate cancer offers the radiobiologic potency of the most intensified radiation therapy regimens but was associated with >90% rates of ulceration of the anterior rectal wall on endoscopic assessment; this infrequently progressed to severe rectal toxicity in prior prospective series. A multi-institutional phase 2 prospective trial was conducted to assess whether placement of a perirectal hydrogel spacer would reduce acute periprostatic rectal ulcer events after high-dose (>40 Gy) SABR. Methods and Materials: Eligible patients included men with stage ≤T2c localized grade group 1 to 3 prostate cancer, a prostate-specific antigen (PSA) level ≤15 ng/mL, American Urological Association Symptom Index = AUA-SI scores ≤18, and a gland volume ≤80 cm3. Patients underwent perirectal hydrogel spacer placement, followed by SABR of 45 Gy in 5 fractions every other day to the prostate only. Androgen deprivation was not allowed except for cytoreduction. The rectal wall was directly assessed by serial anoscopy during follow-up to determine whether the spacer would reduce acute periprostatic rectal ulcer events from >90% to <70% within 9 months of treatment. Results: Forty-four men were enrolled and 43 were eligible for protocol analysis. The median follow-up for surviving patients was 48 months. Acute periprostatic ulcers were observed in 6 of 42 patients (14.3%; 95% confidence interval, 6.0%-27%; P < .001) at a median of 2.9 months posttreatment (range, 1.7-5.6 months). All ulcers (grade 1, 5 ulcers; grade 2, 1 ulcer) resolved on repeat anoscopy within 8 months of incidence. There were no grade ≥3 late gastrointestinal toxicities; the incidence of late grade-2 gastrointestinal toxicities was 14.3%, with a prevalence at 3 years of 0%. No toxicities greater than grade 3 occurred in any domain. Four-year freedom from biochemical failure was 93.8% (95% CI, 85.2%-100.0%). Conclusions: Temporary hydrogel spacer placement before high-dose SABR treatment for localized prostate cancer and use of strict dose constraints are associated with a significant reduction in the incidence of rectal ulcer events compared with prior phase 1/2 trial results. © 2021 Elsevier Inc. |
| Keywords: | follow up; radiotherapy; antigens; urology; toxicity; prostate cancers; diseases; rectal toxicity; phase 2; high dose; rectal wall; gastrointestinal toxicities; hydrogels; methods and materials; prospectives; localised |
| Journal Title: | International Journal of Radiation Oncology, Biology, Physics |
| Volume: | 111 |
| Issue: | 1 |
| ISSN: | 0360-3016 |
| Publisher: | Elsevier Inc. |
| Date Published: | 2021-09-01 |
| Start Page: | 101 |
| End Page: | 109 |
| Language: | English |
| DOI: | 10.1016/j.ijrobp.2021.03.025 |
| PUBMED: | 33753140 |
| PROVIDER: | scopus |
| DOI/URL: | |
| Notes: | Article -- Export Date: 1 September 2021 -- Source: Scopus |
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