68Ga-PSMA PET/CT for Response Assessment and Outcome Prediction in Metastatic Prostate Cancer Patients Treated with Taxane-Based Chemotherapy

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FIGURE 1.
Flowchart of patient selection process.
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FIGURE 2.
Maximum-intensity-projection images of different response scenarios on PSMA PET/CT. PSMA-R: including patients A and B with, respectively, disappearance of all PSMA-positive lesions (CR) or decrease of PSMA-TV > 30% (PR). PSMA-NR: including patients C and D with, respectively, appearance of new lesions and increased PSMA-TV > 30% (PD) or neither new PSMA-positive lesions nor PSMA-TV 30% changes. SD = stable disease.
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FIGURE 3.
Waterfall plot representing individual percentage changes in PSMA-TV (A) and PSA (B) after taxane-based chemotherapy.
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FIGURE 4.
(A and B) Kaplan–Meier plots for OS in whole population (A) and in mCRPC subgroup (B). (C and D) Kaplan–Meier plots for OS for PSMA-R vs. PSMA-NR in whole population (C) and in mCRPC subgroup (D). P values were obtained from log-rank test.

TABLE 1

Patient Characteristics (n = 37)

Characteristic	Data
Age (y)	70 (IQR, 61–74)
ISUP grade
1–3	10 (27%)
4–5	25 (68%)
Unknown	2 (5%)
Primary treatment
Surgery	28 (75%)
Radiotherapy	1 (3%)
Systemic therapy	8 (22%)
Baseline PSA (ng/mL)	27 (IQR, 13–85)
Number of cycles
Docetaxel	6 (range, 4–10)
Cabazitaxel	6 (range, 3–10)
Disease state
mHSPC	8 (22%)
mCRPC	29 (78%)
Patients with metastasis sites
Bone	27 (73%)
Lymph nodes
Pelvic	16 (43%)
Extrapelvic	28 (75%)
Prostatic bed	7 (19%)
Viscera	6 (16%)
Follow-up time (mo)	23 (IQR, 15–30)
First PSMA PET/CT to first cycle (d)	16 (IQR, 9–30)
Last cycle to second PSMA PET/CT (d)	27 (IQR, 18–44)

ISUP = International Society of Urological Pathology.
Qualitative data are number and percentage; continuous data are median and range or IQR.

TABLE 2

Distribution of PSMA PET/CT Responses According to Different PET Parameters and Their Concordance with PSA Response

TABLE 3

Differences Between PSMA-R and PSMA-NR Regarding Different Clinical Factors

Parameter	PSMA-R^*	PSMA-NR^*	P
Age (y)
≤70	11	8	0.248
>70	7	11
ISUP grade
1–3	3	7	0.146
4–5	15	10
Primary therapy
Radical therapy	15	14	0.379
Systemic therapy	3	5
Type of therapy
Docetaxel	13	8	0.065
Cabazitaxel	5	11
Disease stage
mHSPC	8	0	0.001
mCRPC	10	19
Baseline PSA (ng/mL)
≤27	10	8	0.413
>27	8	11
Hemoglobin (g/dL)
≥13	13	7	0.023
<13	5	12
Alkaline phosphatase (IU/L)
≤129	17	12	0.048
>129	1	7

↵* Number of patients (n).
ISUP = International Society of Urological Pathology.
Alkaline phosphatase and hemoglobin were dichotomized according to standard reference value in our laboratory. Age and serum PSA were dichotomized according to median.

TABLE 5

Univariate and Multivariate Cox Regression Analyses Presenting Association of Clinical Factors and PSMA PET/CT Response with OS

	Univariate analysis		Multivariate analysis
Parameter	Hazard ratio	P	Hazard ratio	P
Model 1
PSMA response (yes vs. no)	0.10 (0.03–0.39)	0.001	0.10 (0.02–0.44)	0.003
Log PSA (baseline)	1.78 (1.17–2.72)	0.007	1.46 (0.91–2.34)	0.110
Hemoglobin (baseline)	0.64 (0.50–0.81)	0.001	0.53 (0.36–0.77)	0.001
Model 2
PSMA response (yes vs. no)	0.10 (0.03–0.39)	0.001	0.21 (0.05–0.82)	0.025
Disease state (mHSPC vs. mCRPC)	0.08 (0.01–0.65)	0.019	0.17 (0.02–2.02)	0.162
Log alkaline phosphatase (baseline)	2.63 (1.29–5.36)	0.007	2.07 (0.92–4.67)	0.080