(UroToday.com) The 2023 SNMMI annual meeting included a prostate cancer session, featuring a presentation by Dr. Ahmed Abdelrahman discussing the correlation between total osseous tumor volume and the development of hematologic toxicities in patients with mCRPC receiving 177Lu-PSMA-617. 177Lu-PSMA-617 has been approved for treatment of metastatic castrate resistant prostate cancer based on VISION trial.1 Importantly, the VISION trial excluded patients with extensive bone metastases on bone scans, and as such there is limited data on the efficacy and hematological toxicity of 177Lu-PSMA-617 in patients with high osseous tumor burden.
Hematologic toxicities may limit the application of the radioligand therapy and thus need to be recognized and addressed in a timely manner. In this study presented at SNMMI 2023, Dr. Abdelrahman and colleagues investigated the correlation between the osseous tumor volume measured on 18F piflufolastat PET/CT scans and the development of hematological toxicity related to bone marrow suppression. Additionally, they aimed to develop a reliable and reproducible tool to measure tumor volumes on PET/CT imaging.
All patients who received 177Lu-PSMA-617 radioligand treatment from September 17, 2021 to January 10, 2023 and had pre-therapy 18F piflufolastat PET/CT imaging were included in this study. Serum hematological parameters were measured at baseline, prior to each treatment cycle, 2 to 4 weeks after the treatment, and thereafter as needed. Percent changes in hematological parameters between the baseline and post-therapy values were also calculated, and hematologic toxicity was graded based on CTCAE v 5.0. Patients were further subdivided into 5 subgroups based on post-therapy hematological toxicity level, and osseous and soft tissue tumor volumes were measured using MIM Software® v7.1.7 Segment Lesions research workflow. The correlation between the osseous tumor volume and the percentage change in hematologic parameters were measured using linear regression models, and mean values of the total and osseous tumor volume for each subgroup were calculated.
There were 43 patients that received a total of 135 cycles of 177Lu-PSMA-617 radioligand treatment, and the mean total osseous tumor volume was 594 ml (SD ± 695). The patient baseline characteristics, including mean age, Gleason score, number of cycles completed, total tumor volume, and total osseous volume stratified by CTC toxicity grade after therapy are as follows:
There was a significant correlation between the osseous tumor volume and the percentage of change in hemoglobin levels: p = 0.007 (R2 = 0.16, R2 adj = 0.14)
Similarly, there was a significant correlation between the osseous tumor volume and the percentage of change in platelet levels: p = 0.004 (R2 = 0.19, and R2adj = 0.17)
Dr. Abdelrahman emphasized that the main limitation of this study was the small sample size. Of note, eight patients have received either packed RBCs or platelet transfusions in between cycles for management of acute hematological toxicity.
Dr. Abdelrahman concluded his presentation discussing the correlation between total osseous tumor volume and the development of hematologic toxicities in patients with mCRPC receiving 177Lu-PMSA-617with the following take home messages:
- Significant hematological toxicities were observed in higher osseus tumor volumes
- Assessment of tumor volume appears to give a better understanding of the total tumor burden and distribution and thus it may help to predict the need for transfusion support
- Measurement of tumor volume on PET imaging is easier than using anatomic imaging
- The current segmentation workflow provided a robust and quick tool to perform volume analysis on PET/CT imaging
- Standardization of volume analysis tools is needed to achieve consistent results
Presented by: Ahmed Abdelrahman, MD, Icahn School of Medicine, New York, NY
Written by: Zachary Klaassen, MD, MSc – Urologic Oncologist, Associate Professor of Urology, Georgia Cancer Center, Augusta University/Medical College of Georgia, @zklaassen_md on Twitter during the 2023 Society of Nuclear Medicine and Molecular Imaging (SNMMI) Annual Meeting, Chicago, IL, Sat, June 24 – Tues, June 27, 2023.
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