Abstract
ObjectiveUp to 60% of patients with metastatic, castration-resistant prostate cancer (mCRPC) treated with 177Lu prostate-specific membrane antigen (PSMA) radioligand therapy (RLT) achieves a partial biochemical response with a decrease of > 50% in prostate-specific antigen (PSA) levels. The remaining fractions, however, do not respond to RLT. The aim of this explorative analysis was to identify pre-therapeutic factors for the prediction of response.Methods46 patients [age = 68 years (50–87)] with mCRPC who consecutively underwent RLT with 177Lu PSMA [median applied activity = 6 GBq (2.9–6.2)] were included and analysed retrospectively. The association of different clinical and laboratory factors and parameters from pre-therapeutic 68Ga PSMA positron emission tomography (PET) with the outcome of RLT was tested (Fisher’s test). Outcome was defined as PSA changes 8 weeks after second RLT [partial response (PR), PSA decrease > 50%; progressive disease (PD), PSA increase ≥ 25%; stable disease (SD), others]. Significant predictive factors were combined in a predictive score.Results30% showed a post-treatment PR (median 73% PSA decrease), 35% SD (median 17% PSA decrease) and 35% PD (median 42% PSA increase). Significant predictors for PD were alkaline phosphatase (ALP) > 135 U/l (p = 0.002), PSA > 200 ng/ml (p = 0.036), and maximum standardized uptake value (SUVmax) of the “hottest lesion” in pre-therapeutic PET < 45 (p = 0.005). The predictive score including PSA, ALP and SUVmax could separate 2 distinct groups of patients: ≤ 2 predictive factors (19% PD) and 3 predictive factors (90% PD).ConclusionThe presented predictive score allowed a pre-therapeutic estimate of the expected response to 2 cycles of RLT. As our study was retrospective, prospective trials are needed for validation.
Highlights
Prostate cancer has the highest incidence and the third highest cancer related mortality for men in Europe [1]
The presence of visceral metastases, alkaline phosphatase (ALP) ≥ 220 U/L [5], high platelet count, a regular need for analgesics [6] or elevated lactate dehydrogenase [7] has been identified as a negative predictor for the outcome, whereas ALP < 220 U/L, a cumulative injected activity ≥ 18.8 GBq [8], albumin ≥ 38.6 g/L, aspartate transaminase (AST) ≤ 24 U/L, haemoglobin ≥ 10.4 g/dL, absence of liver metastases [9], and higher standardized uptake value (SUV) mean or max in positron emission tomography (PET) with prostate-specific membrane antigen (PSMA) ligands have been reported to be associated with favourable outcomes [10]
Inclusion criteria were: (1) at least two cycles of radioligand therapy (RLT) with 177Lu PSMA, (2) 68Ga PSMA positron emission tomography (PET)/computed tomography (CT) examination in the same department ≤ 8 weeks prior to first cycle of RLT and (3) complete patient records including follow-up for at least 2 months after second cycle RLT. patients were excluded for the following reasons: PSMA-PET prior to RLT in other facilities or non-PET imaging with PSMA ligands (n = 43) and absence of follow-up after RLT (n = 2), the final study population included patients
Summary
Prostate cancer has the highest incidence and the third highest cancer related mortality for men in Europe [1]. Several treatment options for patients with metastatic, castration-resistant prostate cancer (mCRPC) have become established, including abiraterone, enzalutamide, docetaxel and cabazitaxel [2]. The presence of visceral metastases, alkaline phosphatase (ALP) ≥ 220 U/L [5], high platelet count, a regular need for analgesics [6] or elevated lactate dehydrogenase [7] has been identified as a negative predictor for the outcome, whereas ALP < 220 U/L, a cumulative injected activity ≥ 18.8 GBq [8], albumin ≥ 38.6 g/L, aspartate transaminase (AST) ≤ 24 U/L, haemoglobin ≥ 10.4 g/dL, absence of liver metastases [9], and higher standardized uptake value (SUV) mean or max in positron emission tomography (PET) with PSMA ligands have been reported to be associated with favourable outcomes [10]. The predictive value of these factors varies significantly between studies
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