4058 - 68Ga-PSMA guided bone biopsies for molecular diagnostics in metastatic castration resistant prostate cancer patients

Background

For individual treatment planning in patients with metastatic castration resistant prostate cancer (mCRPC), molecular analyses are increasingly used. As most patients have bone only disease, bone biopsies are often the only source for tumour tissue. However, the success rate of computed tomography (CT)-guided bone biopsies for molecular analyses in mCRPC patients is only 36.5-44%. Positron emission tomography (PET) using ⁶⁸Ga-PSMA is a promising tool to increase the success rate of bone biopsies for molecular analyses in mCRPC patients.

Methods

In this multicenter study, the success rate of ⁶⁸Ga-PSMA guided bone biopsies for molecular diagnostics was retrospectively evaluated in a subset of mCRPC patients who underwent a bone biopsy for whole-genome DNA sequencing within the CPCT-02 study (NCT01855477). To evaluate whether biopsies were obtained from a ⁶⁸Ga-PSMA positive lesion, rigid body image registration of ⁶⁸Ga-PSMA PET/CT and interventional CT was performed. This technique provided volume of interest (VOI) based quantification of ⁶⁸Ga-PSMA uptake at the exact biopsy site. In addition, the potential impact of molecular analyses on clinical decision making was evaluated.

Results

Sixty-nine ⁶⁸Ga-PSMA-guided biopsies were eligible for primary analysis. Based on tumor percentage ≥ 30%, 70% of ⁶⁸Ga-PSMA-guided biopsies was eligible for molecular analyses. At biopsy sites with positive, inconclusive or negative ⁶⁸Ga-PSMA uptake, tumour percentage was ≥ 30% in 73%, 55% and 36% of the biopsies, respectively (p = 0.0850). At sites of biopsies with a tumour percentage ≥ 30%, standardized uptake value (SUV)_max and SUV_mean of ⁶⁸Ga-PSMA were significantly higher (p = 0.0260 and p = 0.0129 respectively), whereas Hounsfield units (HU)_mean and HU_max on CT were significantly lower (p = 0.0189 and p = 0.0494 respectively). Molecular analyses identified potentially targetable aberrations including PTEN loss, AR amplifications, and BRCA variants.

Conclusions

⁶⁸Ga-PSMA PET/CT is a useful technique to improve the success rate of CT-guided bone biopsies for molecular analyses in mCRPC patients. Successful bone biopsies for molecular analyses can improve individual treatment planning by detecting targetable mutations.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

The authors.

Funding

Has not received any funding.

Disclosure

R. de Wit: Advisory / Consultancy, Speaker Bureau / Expert testimony, Research grant / Funding (institution): Sanofi; Advisory / Consultancy, Speaker Bureau / Expert testimony: Merck; Advisory / Consultancy, Research grant / Funding (institution): Bayer; Advisory / Consultancy: Roche; Advisory / Consultancy: Janssen; Advisory / Consultancy: Clovis. N. Mehra: Advisory / Consultancy, Research grant / Funding (institution): Astellas; Advisory / Consultancy, Research grant / Funding (institution): Janssen; Research grant / Funding (institution): Pfizer; Advisory / Consultancy, Research grant / Funding (institution): Roche; Advisory / Consultancy, Research grant / Funding (institution): Sanofi Genzyme; Advisory / Consultancy: MSD; Advisory / Consultancy: BMS; Advisory / Consultancy: Bayer. A.A.M. Van der Veldt: Honoraria (institution), Advisory / Consultancy: BMS; Honoraria (institution), Advisory / Consultancy: MSD; Honoraria (institution), Advisory / Consultancy: Roche; Honoraria (institution), Advisory / Consultancy: Novartis; Honoraria (institution), Advisory / Consultancy: Pierre Fabre; Honoraria (institution), Advisory / Consultancy: Pfizer; Honoraria (institution), Advisory / Consultancy: Sanofi; Honoraria (institution), Advisory / Consultancy: Ipsen. M.P. Lolkema: Research grant / Funding (institution): JNJ; Research grant / Funding (institution): Astellas. All other authors have declared no conflicts of interest.