Prostate radiotherapyCarbon-11 acetate PET/CT based dose escalated IMRT in prostate cancer
Section snippets
Patients
Twelve patients with histologically confirmed adenocarcinoma of prostate and WHO performance status 2 or better referred to external beam radiotherapy were enrolled between January 22 and October 30, 2008. Routine diagnostic workup included serum prostatic specific antigen (PSA), multiple (6–10) bilobal prostatic biopsies, transrectal ultrasound, pelvic computed tomography and bone scan. The median time from biopsy to PET imaging was 4 months (range, 2–6 months). No prior treatment of PCa was
Results
The patient characteristics are listed out in Table 1. All 12 patients were imaged with PET/CT and the injected activity of [11C]acetate was on the average 593 MBq (range 221–786 MBq). In all patients at least one IPL could be detected and 10 patients (83%) had more than one IPL (Table 1). The uptake of the tracer superimposed on fused CT-images of the first six patients is shown in Fig. 1. The maximum SUV ranged from 2.3 to 5.9 g/ml and the total volume of the BTV was on average 4.5 cm3 (0.8–13.9
Discussion
In this study PET/CT imaging with ACE was used to delineate the BTV of 12 patients with PCa. We demonstrated the theoretical feasibility of using the ACE based BTV as a target volume for the dose escalation treatment plans up to 90 Gy by calculating the TCP and NTCP of the rectum and the bladder and by comparing them to a standard IMRT plan.
Preexisting studies of the local progression of PCa suggest that the recurrences after radiotherapy are due to underdosage of the primary tumor area rather
Conclusion
PET/CT imaging with ACE was used to delineate the IPL’s with all 12 patients studied. With SIBIMRT we were able to escalate the dose in the BTV and with all patients the studied TCP was increased without increasing the NTCP of rectum or bladder. By the means of PUC, we determined the optimal dose to be 82.1 Gy to the BTV. Although some non-cancerous tissues such as hyperplasia will receive a high dose as well this should not compromise the improved therapeutic ratio potentially achievable with
Acknowledgments
This study was supported by an EVO grant of the Hospital District of Southwest Finland. The staff of Turku PET centre and Department of Oncology and Radiotherapy are gratefully acknowledged.
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