SBRT for prostate cancer: analysis of CBCT guided radiotherapy and on-line correction
Jose Antonio Solis Campos,
Chile
PO-1484
Abstract
SBRT for prostate cancer: analysis of CBCT guided radiotherapy and on-line correction
Authors: Jose Antonio Solis Campos1, Lisset Gonzalez Abascal1, Gabriel Lazcano Álvarez1, Benjamin Tudela1, Gabriel Veillon Contreras1, Jorge Olivares Gonzalez2
1Universidad de Valparaiso, Radiation Oncology, Valparaiso, Chile; 2Hospital Base de Valdivia, Radiation Oncology, Valdivia, Chile
Show Affiliations
Hide Affiliations
Purpose or Objective
Stereotactic body radiotherapy (SBRT) delivers a high radiation dose to an extracranial target in 1 to 5 fractions. The purpose of this study is to describe the treatment characteristics and toxicities in a cohort of prostate cancer patients treated with CBCT guided SBRT without fiducial markers at Carlos Van Buren Hospital (Chile).
Material and Methods
We performed a retrospective analysis of patients treated with SBRT using flattening filter free volumetric modulated arc therapy between September 2020 and September 2022. Prescription dose was 36.25 Gy to Prostate PTV and 27.25 Gy to seminal vesicles PTV in five fractions (alternate days). On-line correction was performed before each session with CBCT. Patients were treated in an Elekta, Versa HD with Monaco treatment planning system. Acute and late toxicities were registered according to the RTOG grading system.
Results
Two hundred eight patients were included. Median follow up was 9.5 months (IQR 6.2-15.6). Median PSA at diagnosis was 10.83 ng / ml (IQR 6.7-22). Forty-five percent (77) of patients had High Risk disease, among them 44% (34) were studied with PSMA PET / CT. Overall, twenty-six percent (45) of patients were staged with PSMA PET / CT. Median IPSS at diagnosis was 8 points (IQR 5-15). Radiotherapy planning was based on MRI-CT fusion in 80.12% (137) of the patients. Thirty-six percent (62) of patients presented acute grade 1-3 gastrointestinal toxicity and 59.06 % (101) presented grade 1-3 acute urinary toxicity. No grade 4-5 toxicity was observed. Late gastrointestinal toxicity was grade 0 in 42.11%, grade 1 in 10.53 %, grade 2 in 3,51% and grade 3 in 0.58%. No grade 4-5 toxicities were reported. Late urinary toxicity was grade 0 in 39.18%, grade 1 in 9.94%, grade 2 in 6.43% and grade 3 in 0.58%, with only one event grade 4 reported. No grade 5 late urinary toxicity was reported.
| Variable | Median [interquartile range] or N (%) |
| Age (years) | 72 [66-76] |
| PSA at diagnosis (ng/mL) | 10.83 [6.7-22] |
| Baseline IPSS | 8 [5-15] |
NCCN risk Low Intermediate High |
22 (12.87) 69 (40.35) 77 (45.03) |
Staging Conventional* PSMA PET-CT |
115 (67.25) 45 (26.32) |
Planning image CT MRI-CT fusion |
20 (11.70) 137 (80.12) |
| Overall treatment time (days) | 11 [10-13] |
Androgen deprivation therapy No 6 months 12 months 18-36 months |
59 (12.87) 54 (31.58) 2 (1.75) 68 (39.77) |
Acute urinary toxicity 0 1 2 3 4-5 |
61 (35.67) 84 (49.12) 15 (8.77) 2 (1.17) 0 (0) |
Acute gastrointestinal toxicity 0 1 2 3 4-5 |
101 (59.06) 46 (26.90) 12 (7.02) 4 (2.34) 0 (0) |
Late urinary toxicity 0 1 2 3 4 5 |
67 (39.18) 17 (9.94) 11 (6.43) 1 (0.58) 1 (0.58) 0 (0) |
Late gastrointestinal toxicity 0 1 2 3 4-5 |
72 (42.11) 18 (10.53) 6 (3.51) 1 (0.58) 0 (0) |
* Conventional: CT scan +/- bone scintigraphy
Conclusion
CBCT guided SBRT is a safe treatment option, permitting a high dose delivery with excellent acute and late toxicity profiles. Efficacy results will be reported once appropriate follow up is reached.