The early result of whole pelvic radiotherapy and stereotactic body radiotherapy boost for high-risk localized prostate cancer

Abstract

Purpose: The rationale for hypofractionated radiotherapy in the treatment of prostate cancer is based on the modern understanding of radiobiology and advances in stereotactic body radiotherapy (SBRT) techniques. Whole-pelvis irradiation combined with SBRT boost for high-risk prostate cancer might escalate biologically effective dose without increasing toxicity. Here, we report our 4-year results of SBRT boost for high-risk localized prostate cancer.

Methods and materials: From October 2009 to August 2012, 41 patients newly diagnosed, high-risk or very high-risk (NCCN definition) localized prostate cancer were treated with whole-pelvis irradiation and SBRT boost. The whole pelvis dose was 45 Gy (25 fractions of 1.8 Gy). The SBRT boost dose was 21 Gy (three fractions of 7 Gy). Ninety percent of these patients received hormone therapy. The toxicities of gastrointestinal (GI) and genitourinary (GU) tracts were scored by Common Toxicity Criteria Adverse Effect (CTCAE v3.0). Biochemical failure was defined by Phoenix definition.

Results: Median follow-up was 42 months. Mean PSA before treatment was 44.18 ng/ml. Mean PSA level at 3, 6, 12, 18, and 24 months was 0.94, 0.44, 0.13, 0.12, and 0.05 ng/ml, respectively. The estimated 4-year biochemical failure-free survival was 91.9%. Three biochemical failures were observed. GI and GU tract toxicities were minimal. No grade 3 acute GU or GI toxicity was noted. During radiation therapy, 27% of the patient had grade 2 acute GU toxicity and 12% had grade 2 acute GI toxicity. At 3 months, most toxicity scores had returned to baseline. At the last follow-up, there was no grade 3 late GU or GI toxicity.

Conclusions: Whole-pelvis irradiation combined with SBRT boost for high-risk localized prostate cancer is feasible with minimal toxicity and encouraging biochemical failure-free survival. Continued accrual and follow-up would be necessary to confirm the biochemical control rate and the toxicity profiles.

Keywords: CyberKnife; Rapidarc; SBRT boost; high-risk prostate cancer; prostate cancer; radiotherapy; stereotactic body; whole-pelvis radiotherapy.

Figure 1

Isodose curves (A) and dose–volume histogram (B) of whole pelvis radiotherapy for the applied RapidArc plan in the particular patient. (A) The region of the prescription dose (45 Gy), pink color wash; CTV1, red solid line.

Figure 2

Isodose curves (A) and dose–volume histogram (B) of SBRT boost for the applied CyberKnife in the particular patient. (A) The prescription dose (21Gy), blue solid line; CTV1, orange color wash; PTV1, pink color wash.

Figure 3

Toxicity profile with time flame of the patients who underwent whole pelvis radiotherapy with stereotactic body radiotherapy boost. (A) The genitourinary tract toxicity profiles and (B) the gastrointestinal toxicity profile.

Figure 4

Kaplan–Meier curves illustrate the survival of the patients who underwent whole pelvis radiotherapy with stereotactic body radiotherapy boost, including (A) overall survival; 4-year overall survival, 92.2% (B) biochemical recurrence-free survival; 4-year biochemical recurrence-free survival, 91.9%.