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Background: 177 LuPSMA is an effective treatment in metastatic castrate-resistant prostate cancer with trials adopting a standardised dose interval. Adjusting treatment intervals utilising early response biomarkers may improve patient outcomes. Objective: This study evaluated progression-free survival (PFS) and overall survival (OS) based on treatment interval adjustment utilising 177 LuPSMA 24-h SPECT/CT ( 177 Lu-SPECT) and early prostate-specific antigen (PSA) response. Design: Retrospective analysis of a clinical 177 Lu-PSMA-I median PSA-PFS rates were 12.1 months (95%CI: 9.3–17.4), 6.1 months (95%CI: 5.8–9.0), and 2.6 months (95%CI: 1.6–3.1); and OS rates were 19.2 months (95%CI: 16.8–20.7), 13.2 months (95%CI: 12.0–18.8), and 11.2 months (95%CI: 8.7–15.6) for RG 1, 2, and 3, respectively. The median months of ‘treatment holiday’ for RG 1 was 6.1 months (IQR: 3.4–8.7). Nine men had received prior 177 LuPSMA-617 and were retreated with 177 LuPSMA-I&T, with a PSARR of 56% on re-treatment. Conclusion: Personalising dosing regimens using early response biomarkers with 177 LuPSMA has the potential to achieve similar treatment responses to continuous dosing while allowing treatment breaks or intensification. Further evaluation of early response biomarker-guided treatment regimens in prospective trials is warranted. Plain Language Summary Lutetium-PSMA therapy is a new therapy for metastatic prostate cancer that is well tolerated and effective. However, not all men respond equally, with some responding very well and others progressing early. Personalising treatments require tools that can accurately measure treatment responses, preferably early in the treatment course, so adjustments to treatment can be made. Lutetium-PSMA can measure tumour sites after each therapy by taking whole body 3D images at 24 h using a small radiation wave from the treatment itself. This is called a SPECT scan. Previous work has shown that both prostate-specific antigen (PSA) response and changes in tumour volume on a SPECT scan can predict how patients will respond to treatment as early as dose 2. This study demonstrates that stratifying how men are treated based on the results of the 6-week SPECT scan and PSA response potentially allows a third of men to have break in treatment and that these men have both longer time to disease progression and OS. Men with an increase in tumour volume and increase in PSA early in treatment (6 weeks) had shorter time to disease progression and OS. Men with early biomarker disease progression were offered alternative treatments early in an attempt to allow the opportunity to allow a more effective potential therapy, if one was available. The study is an analysis of a clinical programme, and was not a prospective trial. As such, there are potential biases that could influence results. Hence, while the study is encouraging for the use of early response biomarkers to guide better treatment decisions, this must be validated in a well-designed clinical trial.
Emmett et al. (Sun,) studied this question.