EVALUATION OF RESPONSE TO 177LU-PSMA-617 BY SITE SPECIFIC DISEASE IN METASTATIC CASTRATE-RESISTANT PROSTATE CANCER

Abstract

Introduction

In 2022, the FDA approved ¹⁷⁷Lu-PSMA as a promising drug for metastatic castrate-resistant prostate cancer (mCRPC) after the VISION trial. Since then, multiple studies have tried to evaluate the response to ¹⁷⁷Lu-PSMA; however, few studies have described the response depending on the site of disease progression. In our study, we aim to assess the response to ¹⁷⁷Lu-PSMA according to the metastasis sites.

Methods

We queried retrospectively 273 patients who have been treated with ¹⁷⁷Lu-PSMA at Mayo Clinic between April 2022 and September 2023; out of those, we identified 76 (28%) patients who presented with either bone only or lymph node (LN) only disease. Trained research personnel recorded clinicopathological variables; in addition, follow-up imaging and clinical documentation were used to record the treatment outcomes. Chi-square and Kruskal-Wallis tests were used to compare between nominal and continuous variables, respectively.

Results

After the identification of 76 patients, we classified them into two groups according to the site of disease progression: pure bone disease (52 patients, 68%) and pure lymph node disease (24 patients, 32%) without any other sites of disease progression, and both had the same volume of disease. The bone group had a high median initial Gleason score (p=0.0192) and PSA levels (p=0.158) prior to the start of the ¹⁷⁷Lu-PSMA cycles compared with the LN group. With a median follow-up time of 10.2 (IQR: 8.6–11.5) months from the first ¹⁷⁷Lu-PSMA cycle, the post-treatment PSA kinetics did not differ significantly between the two groups; however, patients with LN disease showed a durable response in terms of decreased post-treatment SUVmax of the lesions (p=0.0299) and less radiographic disease progression (p=0.0011) compared with the bone group.

Conclusions

With the limited options for mCRPC patients after receiving several lines of treatment, the ¹⁷⁷Lu-PSMA offers an excellent alternative according to the VISION trial; however, the evaluation of its effect in real-world data is still under investigation. In our study, we found that patients who were treated with ¹⁷⁷Lu-PSMA and had LN only disease showed a durable response compared with those with bone only disease. Further prospective studies to validate our findings are warranted.