Abstract
Recent data suggest that intensity-modulated radiation therapy (IMRT) plus brachytherapy boost for unfavorable prostate cancer provides improved biochemical relapse-free survival over IMRT alone. Stereotactic body radiation therapy (SBRT) may be a less invasive alternative to brachytherapy boost. Here, we report the 3-year gastrointestinal (GI) and genitourinary (GU) toxicities of IMRT plus SBRT boost. Between March 2008 and September 2012, patients with prostate cancer were treated with robotic SBRT (19.5 Gy in three fractions) followed by fiducial-guided IMRT (45-50.4 Gy) on an institutional protocol. Toxicity was prospectively graded using the common terminology criteria for adverse events version 4.0 (CTCAEv.4) at the start of and at 1- to 6-month intervals after therapy. Rectal telangiectasias were graded using the Vienna Rectoscopy Score (VRS). At a median follow-up of 4.2 years (2.4-7.5), 108 patients (4 low-, 45 intermediate-, and 59 high-risk) with a median age of 74 years (55-92) were treated with SBRT plus IMRT, with 8% on anticoagulation and an additional 48% on antiplatelet therapy at the start of therapy. The cumulative incidence of late ≥grade 2 GI toxicity was 12%. Of these, 7% were due to late rectal bleeding, with six patients requiring up to two coagulation procedures. One patient with rectal telangiectasias was treated with hyperbaric oxygen (grade 3 toxicity). No rectal fistulas or stenoses were observed. Ten patients had multiple non-confluent telangiectasias (VRS grade 2), and three patients had multiple confluent telangiectasias (VRS grade 3). The cumulative incidence of late grade 3 GU toxicity was 6%. Most late toxicities were due to hematuria requiring bladder fulguration. There were no late ≥grade 4 GU toxicities. Rates of clinically significant GI and GU toxicities are modest following IMRT plus SBRT boost. Future studies should compare cancer control, quality of life, and toxicity with other treatment modalities for patients with high-risk prostate cancer.
Highlights
Prostate cancer is the most common malignancy in men in the United States, with an estimated 220,800 men diagnosed in 2015 [1]
In an effort to maximize the benefit of administering high doses per fraction and patient acceptance, we have examined the use of stereotactic body radiation therapy (SBRT) as a prostatic boost to image-guided intensity-modulated radiation therapy (IMRT) for the treatment of patients with unfavorable clinically localized prostate cancer
From March 2008 to September 2012, 108 prostate cancer patients were treated on an institutional IMRT plus Stereotactic body radiation therapy (SBRT) boost protocol
Summary
Prostate cancer is the most common malignancy in men in the United States, with an estimated 220,800 men diagnosed in 2015 [1] Of these patients, approximately 15% present with high-risk disease [2]. Several institutional series have reported favorable outcomes, with biochemical control rates of 87–88 and 69% at 5–7 years for intermediate- and high-risk disease, respectively [10,11,12,13]. These results have subsequently been confirmed in randomized trials [14, 15]. We report the 3-year gastrointestinal (GI) and genitourinary (GU) toxicities of IMRT plus SBRT boost
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