Feasibility of Dose Escalating [18F]fluciclovine Positron Emission Tomography Positive Pelvic Lymph Nodes During Moderately Hypofractionated Radiation Therapy for High-Risk Prostate Cancer

Andrew M McDonald; Samuel J Galgano; Jonathan E McConathy; Eddy S Yang; Michael C Dobelbower; Rojymon Jacob; Soroush Rais-Bahrami; Jeffrey W Nix; Richard A Popple; John B Fiveash

doi:10.1016/j.adro.2019.05.008

Feasibility of Dose Escalating [¹⁸F]fluciclovine Positron Emission Tomography Positive Pelvic Lymph Nodes During Moderately Hypofractionated Radiation Therapy for High-Risk Prostate Cancer

Adv Radiat Oncol. 2019 Jun 19;4(4):649-658. doi: 10.1016/j.adro.2019.05.008. eCollection 2019 Oct-Dec.

Authors

Andrew M McDonald^{1

2}, Samuel J Galgano³, Jonathan E McConathy³, Eddy S Yang^{1

2}, Michael C Dobelbower^{1

2}, Rojymon Jacob^{1

2}, Soroush Rais-Bahrami^{2

4}, Jeffrey W Nix^{2

4}, Richard A Popple¹, John B Fiveash^{1

2}

Affiliations

¹ Department of Radiation Oncology, University of Alabama at Birmingham, Birmingham, Alabama.
² Comprehensive Cancer Center, University of Alabama at Birmingham, Birmingham, Alabama.
³ Department of Radiology, University of Alabama at Birmingham, Birmingham, Alabama.
⁴ Department of Urology, University of Alabama at Birmingham, Birmingham, Alabama.

Abstract

Purpose: The aim of this study was to report the treatment planning feasibility of dose escalation to suspicious lymph nodes (LNs) for a series of men who underwent pretreatment [¹⁸F]fluciclovine positron emission tomography (PET)/magnetic resonance imaging (MRI).

Methods and materials: Cases of men with prostate cancer who enrolled in a clinical trial of pretreatment [¹⁸F]fluciclovine PET who had suspicious LNs were selected. Pelvic LNs <1 cm were defined as positive based on [¹⁸F]fluciclovine-PET if their maximum standardized uptake value (SUV_max) was ≥1.3-fold greater than the reference blood pool SUV_mean, and LNs ≥1 cm were defined as positive if the SUV was greater than the reference SUV bone marrow reference. For each case, a radiation treatment plan was generated to deliver 70 Gy to the prostate and proximal seminal vesicles, 60.2 Gy to the PET-positive LNs, and 50.4 Gy to the elective nodal regions, simultaneously in 28 fractions of 2.5 Gy, 2.15 Gy, and 1.8 Gy, respectively. Treatment planning goals were defined a priori. The resulting target volume and organ-at-risk dosimetry were compared with the original treatment plan.

Results: Four cases were identified, with between 1 and 5 [¹⁸F]fluciclovine PET-positive LNs each. Goals for the prostate and elective nodal target volumes were successfully met in all cases. The goal of covering more than 90% of the positive LN planning target volume by the prescription dose of 60.2 Gy was met in 3 of the 4 cases. This goal was not met in 1 case, but 100% of clinical target volume was covered by 60.2 Gy. The primary organ-at-risk tradeoff was that a small volume (0.5-8.2 cm³) of small bowel would receive ≥54 Gy in each case.

Conclusions: These preliminary results suggest that [¹⁸F]fluciclovine PET/MRI directed dose escalation of suspicious pelvic LNs is likely feasible in the setting of definitive radiation therapy. The potential clinical benefit of dose escalating [¹⁸F]fluciclovine PET-positive LNs should be investigated in a prospective clinical trial.