Integration of 68Ga-PSMA-PET imaging in planning of primary definitive radiotherapy in prostate cancer: a retrospective study

Abstract

BackgroundProstate cancer (PC) is one of the most commonly treated cancer entities with radiation therapy (RT). Risk group-adapted treatment and avoidance of unnecessary toxicities relies primarily on accurate tumor staging. Thus, the introduction of prostate-specific membrane antigen (PSMA) in diagnosis and treatment of PC is a highly interesting development in radiation oncology of urologic tumors. The present work is to evaluate the integration of 68Ga-PSMA-PET imaging into standard radiation planning of primary definitive treatment of PC and to determine the impact of PSMA imaging on tumor staging.MethodsThe data of 15 patients treated for PC between August 2013 and April 2015 were evaluated. Treatment planning included 68Ga-PSMA-PET imaging. We analyzed whether the use of PSMA-imaging led to a change of the TNM stage and if it influenced the RT treatment approach or the target volume, due to changes in the gross tumor volume (GTV) or clinical target volume (CTV), in the final treatment plan.ResultsIn 53.3 % of the analyzed patients a change occurred in the TNM stage based on 68Ga-PSMA-PET examination. The RT concept changed in 33.3 % of all patients, leading to relevant changes in the planning target volume. Among these, an additional irradiation of the pelvic lymph drainage due to tracer uptake in lymph nodes was performed in 25 %. Furthermore, boost volumes of PET-positive lymph nodes were added in 80 % of these cases. A down staging due to the 68Ga-PSMA-PET examination occurred in 13.3 % of all cases.ConclusionsThe integration of 68Ga-PSMA-PET-imaging into the RT treatment planning process can be useful for detailed target volume planning. The performance of a 68Ga-PSMA-PET frequently leads to changes in the TNM stage, altering the RT treatment regimen and the target volume. A prospective trial is underway to evaluate the impact of 68Ga-PSMA-PET based treatment planning on outcome.

Prostate-Specific Membrane Antigen Ligands for Imaging and Therapy

“…Morigi et al prospectively evaluated the impact on management of 68 Ga-PSMA-11 in patients with BCR and prior 18 F-fluorocholine treatment; they demonstrated a major impact in approximately one-third of patients, especially those with a low PSA level (78). Two other studies reported similar results (91,92). Data are limited in patients with metastatic disease.…”

PSMA Ligands for PET Imaging of Prostate Cancer

“…Several studies have investigated the impact of PSMA ligand PET/CT on patient management and therapy. Most studies have focused on the value of PSMA ligand PET/CT in patients with BCR after curative treatment and have reported changes in therapeutic management depending on the specific clinical scenario and the extent of treatment modification (69)(70)(71)(72)(73)(74). Most recently, an overall change in the therapeutic management of 75% of 131 patients after primary treatment was shown (69).…”

“…In a well-defined patient cohort before salvage radiotherapy, a major management change in 20 of 70 patients (28.6%) with a PSA level of less than 1 ng/mL was demonstrated by van Leeuwen et al (74). In the setting of primary treatment, a small cohort of 15 patients underwent PSMA ligand PET/CT, and the imaging was found to influence clinical TNM stage in 53.3% of patients and radiotherapy plan in 33.3% (71). Combining the settings of radiotherapy planning in both primary and recurrent disease, 2 recent publications reported PSMA ligand PET/CT to have an impact on 50.8% and 53.7% of patients (72,73).…”

Impact of 68Ga-PSMA PET/CT on salvage radiotherapy planning in patients with prostate cancer and persisting PSA values or biochemical relapse after prostatectomy

“…A recently published meta-analysis summarized the available studies and reported in patients with BCR an overall positivity rate of 76 % [27]. However, only limited data are available regarding the impact of 68 Ga-PSMA PET/CT on SRT planning [28–30]. Change of treatment based on the 68 Ga-PSMA PET/CT findings has been reported in 50.8 and 53.7 % of patients, but these cohorts included primary disease and BCR [29, 30].…”

“…Change of treatment based on the 68 Ga-PSMA PET/CT findings has been reported in 50.8 and 53.7 % of patients, but these cohorts included primary disease and BCR [29, 30]. Dewes et al found a change of TNM stage in 53.3 % and a change in RT concept in 33.3 % of cases prior to initial curative RT [28]. Patient cohorts were heterogeneous, and only very limited data are available on patient outcome in 68 Ga-PSMA PET/CT-guided RT [31].…”