Keywords:
Outcomes, Radiation therapy / Oncology, Cone beam CT, Oncology, Genital / Reproductive system male, Radiotherapy techniques
Authors:
S. Chin, A. Fatimilehin, R. Walshaw, H. Mistry, T. Elliot, J. Logue, J. Wylie, A. Choudhury; Manchester/UK
DOI:
10.26044/ranzcr2019/R-0109
Results
-
The number of FFBF, DM, CSM and OS events were 53, 15, 11 and 29 respectively. Kaplan Meier estimates for FFBF at 5 and 10 years was 68% (95% CI 59%-77%) and 51% (95% CI 43%-62%). Kaplan Meier estimates for OS at 5 and 10 years was 90% (95% CI 85%-96%) and 75% (95% CI 68%-84%). Cumulative incidence of DM at 5 and 10 years was 7% (95% CI 2%-12%) and 16% (95% CI 8%-23%). Cumulative incidence of CSM at 5 and 10 years was 5% (95% CI 1%-10%) and 11% (95% CI 14%-17%).
-
Figure 1 demonstrates FFBF, DM, CSM and OS for the whole cohort. FFBF for early SRT compared to late SRT was 81% vs 66% at 5 years and 68% vs 49% at 10 years. Figure 2 demonstrates FFBF stratified by pre-SRT PSA level. On multivariable analysis, pre-RT PSA, ISUP grade group, SVI, and ADT use were associated with FFBF (Table 2).
Table 2: Univariable and multivariable analysis of freedom from biochemical failure for patients treated with hypofractionated salvage prostate bed radiotherapy
FFBF
|
Univariable analysis
|
Multivariable analysis
|
|
sHR
|
95% CI
|
P
|
sHR
|
95% CI
|
P
|
Age at RT
|
0.98
|
0.94-1.03
|
0.41
|
0.98
|
0.92-1.04
|
0.47
|
Initial PSA
|
1.03
|
1.01-1.05
|
<0.01
|
0.96
|
0.90-1.03
|
0.23
|
PSA pre SRT
|
1.26
|
1.15-1.39
|
<0.01
|
1.49
|
1.01-2.19
|
0.04
|
ISUP (GG 3-5)
|
1.50
|
0.87-2.59
|
0.15
|
1.69
|
0.93-3.07
|
0.09
|
PSM
|
0.78
|
0.42-1.45
|
0.43
|
0.83
|
0.44-1.58
|
0.58
|
EPE
|
2.06
|
1.21-3.52
|
<0.01
|
2.00
|
1.07-3.73
|
0.03
|
SVI
|
3.50
|
1.70-7.21
|
<0.01
|
3.03
|
1.37-6.71
|
<0.01
|
ADT (no vs yes)
|
3.13
|
0.91-11.1
|
0.07
|
7.14
|
1.56-33.3
|
0.01
|
Abbreviations: sHR = sub-distribution hazard ratio, CI = confidence interval, RT = radiotherapy, PSA = prostate specific antigen, SRT = salvage radiotherapy, ISUP GG = International Society of Urological Pathology Grade Group, PSM = positive surgical margins, EPE = extraprostatic extension, SVI = seminal vesicle invasion, ADT = androgen deprivation therapy
-
We found that the final nomogram score was a predictor for BF, HR = 2.82 (1.81-4.39), concordance index = 0.67 (S.E. = 0.04) and log-rank p<0.001. The model predicted a population 5 and 10-year FFBF fraction of 0.78 and 0.67 whereas the observed was 0.67 (95% CI: 0.59-0.76) and 0.51 (0.42-0.61) respectively. We further assessed the models’ predictive power by plotting the predicted against observed 5 and 10-year FFBF for 4 groups based on the 25th, 50th and 75th percentiles of the risk scores (Figure 3).