June 15, 2022 – Current guidelines used to plan rescue radiotherapy in patients with local recurrence of prostate cancer need to be updated to take into account information from new imaging modalities, such as PSMA PET, according to a study presented in Society for Nuclear Medicine and Molecular Imaging Annual Meeting for 2022 The study has shown that PSMA PET is effective in identifying relapses that are partially or completely outside the clinical target range, as defined by these guidelines. This suggests that PSMA PET may be an invaluable tool for therapy planning.
Following a biochemical recurrence of prostate cancer, rescue radiation therapy may be a curative approach. This therapy is performed following contouring guidelines based on expert consensus, such as Oncology group in radiation therapy (RTOG) guidelines. In today’s era of precision medicine, the study’s authors seek to determine whether PSMA PET images can provide more detailed data on relapse patterns to inform treatment planning.
Patients with prostate cancer who had a biochemical recurrence after radical prostatectomy were included in the analysis if their PSMA PET / CT images showed recurrence in the prostate bed. To analyze recurrence patterns, two nuclear physicians documented areas of recurrence of PSMA PET / CT, and four radiation oncologists (masked for PSMA PET / CT findings) delineated the clinical target volume using RTOG guidelines on PET CT images. CT. PSMA recurrence sites were then compared to RTOG-based clinical target volumes.
Recurrences of PSMA were fully covered by clinical target volumes in 54 percent of patients. In 34 percent of patients, recurrence of PSMA was only partially covered, and in 13 percent of patients, recurrence of PSMA was localized entirely outside the clinical target volume.
“This study has the potential to redefine the guidelines for contouring the prostate bed to improve the therapeutic ratio for patients receiving postoperative radiation therapy,” they said. Ida Sonny, Ph.D., a project scientist in the Department of Radiology at the University of California, Los Angeles. “Advances in nuclear medicine and molecular imaging, such as PSMA PET, have the ability to guide individualized, personalized treatments that will ultimately benefit all our patients.”
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