Patterns of Failure After Prostate-Only Radiotherapy in High-Risk Prostate Cancer: Implications for Refining Pelvic...

Area of Science:

• Oncology
• Radiotherapy
• Nuclear Medicine

Background:

• Prostate-only radiotherapy (PORT) is a curative option for high-risk prostate cancer.
• Understanding relapse patterns after PORT is crucial for optimizing treatment and follow-up strategies.
• Gallium-68 PSMA-PETCT (Ga⁶⁸PSMA-PETCT) has emerged as a sensitive tool for detecting prostate cancer recurrence.

Purpose of the Study:

• To investigate the patterns of relapse detected by Ga⁶⁸PSMA-PETCT at biochemical failure (BCF) after PORT in high-risk prostate cancer.
• To evaluate the implications of these relapse patterns on current pelvic lymph node contouring recommendations.

Main Methods:

• Retrospective analysis of 68 patients with high-risk, node-negative prostate cancer treated with PORT and androgen deprivation therapy (ADT).
• Patients underwent Ga⁶⁸PSMA-PETCT at biochemical failure.
• Patterns of regional and distant recurrence were analyzed, with specific attention to pelvic lymph node recurrence locations relative to anatomical landmarks and existing contouring guidelines.

Main Results:

• 46% of patients experienced regional recurrence, and 46% had distant recurrence.
• Among nodal recurrences, 46% had no distant metastases.
• The lowest nodal recurrence was observed 20 mm cranial to the pubic symphysis, influencing the evaluation of established contouring guidelines (RTOG, GETUG, PIVOTAL, NRG, GFRU).

Conclusions:

• Pelvic failures represent a significant proportion of recurrences following PORT.
• The observed caudal extent of nodal recurrence necessitates a review and potential revision of pelvic lymph node contouring guidelines.
• Ga⁶⁸PSMA-PETCT provides valuable insights into relapse patterns, aiding in the refinement of radiotherapy planning.