Abstract
BackgroundClinical data indicates that delivery of larger daily doses of radiation may improve the therapeutic ratio for prostate cancer compared to conventional fractionation. A phase II study of stereotactic body radiotherapy with real-time motion management and daily plan re-optimization for low to intermediate risk prostate cancer was undertaken to evaluate this hypothesis. This report details the toxicity and quality of life following treatment.MethodsFrom 2009 to 2013, 60 patients with T1–T2c prostate cancer with a Gleason score of 6 and PSA ≤ 15 or Gleason score of 7 and PSA ≤ 10 were enrolled. Patients with nodal metastases, an American Urological Association symptom score > 18, or gland size > 100 g were not eligible. Patients were treated to 37 Gy in 5 fractions. Early and late genitourinary and gastrointestinal toxicity were graded based on NCI CTCAE v4.0 and quality of life was assessed by the American Urological Association symptom score, International Index of Erectile Function, and Expanded Prostate cancer Index Composite Short Form up to 36 months after treatment.ResultsAfter a median follow-up of 27.6 months, no grade 3 or greater genitourinary toxicity was observed. Four patients (6.7%) reported a late grade 2 genitourinary toxicity. One patient (1.7%) reported a late grade 3 gastrointestinal toxicity. Five patients (8.3%) developed a late grade 2 gastrointestinal toxicity. The median American Urological Association symptom score increased from 4.5 prior to treatment to 11 while on treatment (p < 0.01), but was 5 at 36 months post-treatment (p = 0.65). Median International Index of Erectile Function scores decreased from 19 to 17 over the course of follow-up (p < 0.01). Only median scores within the Expanded Prostate Cancer Index Composite Short Form sexual domain were significantly decreased at 36 months post-treatment (67.9 vs 45.2, p = 0.02). There was no significant difference in median score within the urinary, bowel, or hormonal domains at 36 months of follow-up.ConclusionsStereotactic body radiotherapy for low to intermediate risk prostate cancer is well tolerated with limited toxicity or decrease in quality of life. Longer follow-up is necessary to assess the efficacy of treatment.Trial registrationClinicaltrials.gov NCT00941915 Registered 17 June 2009.
Highlights
Clinical data indicates that delivery of larger daily doses of radiation may improve the therapeutic ratio for prostate cancer compared to conventional fractionation
There is clinical data [5, 6] that suggests that prostate cancer has a low α/β compared to surrounding normal tissues and increasing daily radiation fraction size will have a greater effect on the tumor and increase the therapeutic ratio
The seminal vesicles were not included in the clinical target volume (CTV) as the risk of this in patients with a combined Gleason score of seven but primary Gleason score of three has been shown to be 4% [13]
Summary
Clinical data indicates that delivery of larger daily doses of radiation may improve the therapeutic ratio for prostate cancer compared to conventional fractionation. Conventional treatment of localized prostate cancer with radiation alone involves doses to 74 Gy or greater given over 8 to 9 weeks This regimen is based on four randomized trials showing improved progression free survival compared to lower cumulative doses, at the cost of increased toxicity [1,2,3,4]. Given this concomitant increase in toxicity with dose, as well as the expense and inconvenience of protracted courses, alternative treatment schemes have been investigated. Hypofractionation, or the delivery of fewer, larger fractions to a lower total dose, may allow for increased tumor control and limit the toxicity and practical disadvantages of dose escalation
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