(UroToday.com) The 2024 European Association of Urology (EAU) annual congress held in Paris, France between April 5th and 8th was host to an abstract session on treatment intensification to improve prostate cancer outcomes. Dr. Elio Mazzone presented the results of an analysis evaluating the ‘optimal’ definition of PSA response following metastasis-directed therapy (MDT) in men with oligo recurrent prostate cancer detected on PSMA PET/CT.
Dr. Mazzone noted that MDT is a treatment option for patients with biochemical recurrence and evidence of oligoprogressive disease on PSMA PET following definitive local therapy. However, it remains unclear whether PSA levels post-MDT can be reliably used to determine treatment response and, if so, which PSA value can best discriminate those patients at higher risk of further metastatic progression. Thus, the objective of this study was to identify the most ‘informative’ PSA value after MDT for predicting further metastatic progression.
The study investigators retrospectively identified 383 patients treated with radical prostatectomy between 1998 and 2022 and who were evaluated with PSMA PET for biochemical recurrence between 2016 and 2023. Among these, 247/383 (64%) had ≤5 metastases on PSMA PET. Of these 247 patients, 116 (47%) received MDT (final study cohort). MDT consisted of stereotactic ablative radiation therapy (SABR) for the PSMA PET positive lesions (nodal, bony, or visceral). Serum PSA levels were measured at three months following MDT, and then every three months thereafter.
The primary study endpoint was clinical recurrence, defined as the development of new metastases on follow-up PSMA PET following MDT. Multivariable Cox regression modeling was used examine the association between the first post-MDT PSA value and clinical recurrence, adjusting for pre-MDT PSA, number of positive spots, and concomitant use of ADT. The C-index was used to identify the ideal PSA cut-off value with the highest accuracy.
The median PSA at PSMA PET was 0.9 ng/ml. The median follow-up post-MDT was 30 months. Overall, 44/116 patients had evidence of clinical recurrence. On multivariable regression analysis, the first (i.e., 3 months) PSA value after MDT was a significant predictor of clinical recurrence (p<0.01). The PSA value associated with the highest accuracy was 0.42 ng/ml (c-index: 76%). When patients were stratified by this PSA cut-off value, the 3-year clinical recurrence-free survival rates were 75% for those with a 3-month post-MDT PSA value of <0.4 ng/ml and 28% for those with a PSA >0.4 ng/ml.
Dr. Mazzone concluded that among patients with a positive PSMA PET who are treated with MDT, a PSA value of 0.4 ng/ml at 3 months post-MDT can be reliably used as a cut-off for defining treatment response since it best discriminates patients at higher risk of further clinical recurrence during follow-up.
Presented by: Elio Mazzone, MD, Consultant Urologist, IRCCS San Raffaele Scientific Institute - Vita-Salute San Raffaele University, Unit of Urology - Division of Oncology - Gianfranco Soldera Prostate Cancer Lab, Milan, Italy
Written by: Rashid Sayyid, MD, MSc - Society of Urologic Oncology (SUO) Clinical Fellow at The University of Toronto, @rksayyid on Twitter during the 2024 European Association of Urology (EAU) annual congress, Paris, France, April 5th - April 8th, 2024