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. 2018 Jun;10(3):193-201.
doi: 10.5114/jcb.2018.76881. Epub 2018 Jun 29.

Phase I study of dose escalation to dominant intraprostatic lesions using high-dose-rate brachytherapy

Christopher H Chapman  1 , Steve E Braunstein  1 , Jean Pouliot  1 , Susan M Noworolski  2 , Vivian Weinberg  1 , Adam Cunha  1 , John Kurhanewicz  2 , Alexander R Gottschalk  1 , Mack Iii Roach  1 , I-Chow Hsu  1
Affiliations

Phase I study of dose escalation to dominant intraprostatic lesions using high-dose-rate brachytherapy

Christopher H Chapman et al. J Contemp Brachytherapy. 2018 Jun.

Abstract

Purpose: Radiation dose escalation for prostate cancer improves biochemical control but is limited by toxicity. Magnetic resonance spectroscopic imaging (MRSI) can define dominant intraprostatic lesions (DIL). This phase I study evaluated dose escalation to MRSI-defined DIL using high-dose-rate (HDR) brachytherapy.

Material and methods: Enrollment was closed early due to low accrual. Ten patients with prostate cancer (T2a-3b, Gleason 6-9, PSA < 20) underwent pre-treatment MRSI, and eight patients had one to three DIL identified. The eight enrolled patients received external beam radiation therapy to 45 Gy and HDR brachytherapy boost to the prostate of 19 Gy in 2 fractions. MRSI images were registered to planning CT images and DIL dose-escalated up to 150% of prescription dose while maintaining normal tissue constraints. The primary endpoint was genitourinary (GU) toxicity.

Results: The median total DIL volume was 1.31 ml (range, 0.67-6.33 ml). Median DIL boost was 130% of prescription dose (range, 110-150%). Median urethra V120 was 0.15 ml (range, 0-0.4 ml) and median rectum V75 was 0.74 ml (range, 0.1-1.0 ml). Three patients had acute grade 2 GU toxicity, and two patients had late grade 2 GU toxicity. No patients had grade 2 or higher gastrointestinal toxicity, and no grade 3 or higher toxicities were noted. There were no biochemical failures with median follow-up of 4.9 years (range, 2-8.5 years).

Conclusions: Dose escalation to MRSI-defined DIL is feasible. Toxicity was low but incompletely assessed due to limited patients' enrollment.

Keywords: focal; image-guided brachytherapy; intraprostatic; prostate cancer.

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Conflict of interest statement

The authors report no conflict of interest.

Figures

Fig. 1
Fig. 1
Example treatment plan of patient treated with 150% boost of dominant intraprostatic lesions (DIL) in left peripheral zone. Shaded areas are prostate clinical target volume (CTV), urethra, DIL, and rectum. Isodose lines are 50%, 100%, and 150% of prescription dose. A) treatment planning computed tomography (CT). B) T2-weighted magnetic resonance imaging with DIL outline registered to treatment planning CT
Fig. 2
Fig. 2
Eligibility and inclusion flowchart
Fig. 3
Fig. 3
Treatment toxicity by grade, CTCAE version 4
Fig. 4
Fig. 4
Change in IPSS from pre-treatment score by individual patient and median change up to 12 months posttreatment
See this image and copyright information in PMC

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