Combination of ^99mTc-Labeled PSMA-SPECT/CT and Diffusion-Weighted MRI in the Prediction of Early Response After Carbon Ion Therapy in Prostate Cancer: A Non-Randomized Prospective Pilot Study

Figures & data

Table 1 The Clinical Characteristics of All the Patients

No. of Patients	n=26
Age (years)
Median	66.5
IQR	58.8–72.8
Gleason score
6	9
7	5
8	8
9	4
T staging
T1	2
T2	19
T3	3
T4	2
Risk groups*
Intermediate	8
High	9
Very high	9
Pre-treatment PSA value (ng/mL)
Median	7.09
After treatment PSA value (ng/mL)
Median	1.65

Note: *These patients were classified into prognostic risk groups based on the National Comprehensive Cancer Network (NCCN) criteria.

Abbreviations: IQR, interquartile range; PSA, prostate specific antigen.

Table 2 Comparison of MRI, PSMA-SPECT/CT and Clinical Parameters Between Good Responders and Poor Responders

Parameters	Good Responders (N=21)	Poor Responders (N=5)	P value^†	AUC
TBR
Before CIRT	16.277±15.746	10.591±8.874	0.200	NA
After CIRT	5.091±3.176	7.231±2.201	0.019	NA
Δ TBR	−0.582±0.255	−0.141±0.300	0.010	0.867
ADCmean (× 10^−3 mm^2/s)
Before CIRT	0.741±0.199	0.892±0.201	0.138	NA
After CIRT	1.189±0.136	1.099±0.216	0.374	NA
Δ ADCmean	0.719±0.508	0.253±0.223	0.028	0.819
Gleason Score (No. pts)
6–7	13	1	0.091	NA
8–9	8	4
Risk Group (No. pts)
Intermediate	7	1	0.413	NA
High	8	1
Very high	6	3

Note: ^†Comparison between good responders and poor responders.

Abbreviations: MRI, magnetic resonance imaging; PSMA, prostate-specific membrane antigen; SPECT/CT, single photon emission computed tomography/computed tomography; TBR, tumor/background ratio; CIRT, Carbon ion radiotherapy; ADC_mean, mean value of apparent diffusion coefficient; AUC, area under the curve; NA, not available.

Figure 1 TBR (A) and ADC (B) changes after CIRT of good responders and poor responders. *p< 0.05.

Figure 2 Scatter-plot showing relationship between Δ TBR and Δ ADC_mean after CIRT.

Figure 3 ROC curves used to evaluate good response to CIRT with Δ TBR, Δ ADC_mean and combined used of Δ TBR and Δ ADC_mean, AUC of Δ TBR (0.867) was higher than that of Δ ADC_mean (0.819). AUC increased with combined used of Δ TBR and Δ ADC_mean (0.895).

Figure 4 A patient with pathology confirmed prostate cancer of Gleason score 4+4 (T3bN0M0, very high risk) who showed good response after CIRT. PSMA uptake (A) was visualized on the prostate with TBR of 34.9. After CIRT, the SPECT/CT (D) showed PSMA uptake was significantly decreased with TBR of 3.4. Axial T1 weighted MRI showed the tumor before (B) and after (E) CIRT. In baseline ADC map (C), ADC_mean was 0.616×10⁻³ mm²/s. In post CIRT ADC map (F), ADC_mean was 1.205 × 10^–3 mm²/s.

Figure 5 A patient with pathology confirmed prostate cancer of Gleason score 5+4 (T3aN0M0, very high risk) who showed poor response after CIRT. PSMA uptake (A) was visualized on the prostate with TBR of 4.87. After CIRT, the PSMA (D) uptake was still visualized on the prostate (TBR, 3.4). Axial T1 weighted MRI showed the tumor before (B) and after (E) CIRT. In baseline ADC map (C), ADC_mean was 0.787× 10^–3 mm²/s. In post CIRT ADC map (F), ADC_mean was 0.812 × 10^–3 mm²/s.