Stereotactic Body Radiotherapy as Monotherapy or Post–External Beam Radiotherapy Boost for Prostate Cancer: Technique, Early Toxicity, and PSA Response

Department of Radiation Oncology, University of California San Francisco, San Francisco, California, USA.
International journal of radiation oncology, biology, physics (Impact Factor: 4.18). 12/2010; 82(1):228-34. DOI: 10.1016/j.ijrobp.2010.10.026
Source: PubMed

ABSTRACT High dose rate (HDR) brachytherapy has been established as an excellent monotherapy or after external-beam radiotherapy (EBRT) boost treatment for prostate cancer (PCa). Recently, dosimetric studies have demonstrated the potential for achieving similar dosimetry with stereotactic body radiotherapy (SBRT) compared with HDR brachytherapy. Here, we report our technique, PSA nadir, and acute and late toxicity with SBRT as monotherapy and post-EBRT boost for PCa using HDR brachytherapy fractionation.
To date, 38 patients have been treated with SBRT at the University of California-San Francisco with a minimum follow-up of 12 months. Twenty of 38 patients were treated with SBRT monotherapy (9.5 Gy × 4 fractions), and 18 were treated with SBRT boost (9.5 Gy × 2 fractions) post-EBRT and androgen deprivation therapy. PSA nadir to date for 44 HDR brachytherapy boost patients with disease characteristics similar to the SBRT boost cohort was also analyzed as a descriptive comparison.
SBRT was well tolerated. With a median follow-up of 18.3 months (range, 12.6-43.5), 42% and 11% of patients had acute Grade 2 gastrourinary and gastrointestinal toxicity, respectively, with no Grade 3 or higher acute toxicity to date. Two patients experienced late Grade 3 GU toxicity. All patients are without evidence of biochemical or clinical progression to date, and favorably low PSA nadirs have been observed with a current median PSA nadir of 0.35 ng/mL (range, <0.01-2.1) for all patients (0.47 ng/mL, range, 0.2-2.1 for the monotherapy cohort; 0.10 ng/mL, range, 0.01-0.5 for the boost cohort). With a median follow-up of 48.6 months (range, 16.4-87.8), the comparable HDR brachytherapy boost cohort has achieved a median PSA nadir of 0.09 ng/mL (range, 0.0-3.3).
Early results with SBRT monotherapy and post-EBRT boost for PCa demonstrate acceptable PSA response and minimal toxicity. PSA nadir with SBRT boost appears comparable to those achieved with HDR brachytherapy boost.

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Available from: Martina Descovich, Mar 11, 2014
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    • "The current evidence for SABR as primary treatment for localized PCa is mainly in the form of small trials or series, 13 using Cyberknife™ and 6 using linacs [18] [19] [20] [21] [22] [23] [24]. There is variation in dose-fractionation schedules, organ-at-risk constraints, use of androgen deprivation, CTV–PTV margins, IGRT techniques and inclusion of SV within the CTV (most often the SV are not treated, even in non-low risk patients). "
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    • "Since the early reports of hypofractionation, there has been a steady increase in reports of hypofractionated radiotherapy for prostate cancer . Some have decreased the number of fractions modestly, and others have reduced it to only five sessions [41] [42] [43] [44] [45] [46] [47] [48] [49] [50]. "
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    03/2013; 2013:103547. DOI:10.1155/2013/103547
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    • "In contrast, in a multi-institutional CyberKnife SBRT clinical study (Meier et al., 2010), the PTV is covered at 36.25 Gy, but the prostate GTV receives at least 40 Gy. Even more confounding to direct comparisons is the HDR-like dosimetry used in some centers (Fuller, 2008; Jabbari et al., 2010) whereby the prescription dose is 38 Gy delivered in four fractions, but the delivered dose to the peripheral zone is much higher and the urethra is contoured and urethral dose constrained (Fuller, 2008; Jabbari et al., 2010). Also, in two recently published studies patients were treated every other day (King et al., 2009; Boike et al., 2011), which may impact the efficacy and toxicity due to repair that may take place in the 48-h period between fractions. "
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