Does Local Recurrence of Prostate Cancer After Radiation Therapy Occur at the Site of Primary Tumor? Results of a Longitudinal MRI and MRSI Study

Department of Radiology and Biomedical Imaging, University of California San Francisco, California, USA.
International journal of radiation oncology, biology, physics (Impact Factor: 4.26). 02/2012; 82(5):e787-93. DOI: 10.1016/j.ijrobp.2011.11.030
Source: PubMed


To determine if local recurrence of prostate cancer after radiation therapy occurs at the same site as the primary tumor before treatment, using longitudinal magnetic resonance (MR) imaging and MR spectroscopic imaging to assess dominant tumor location.
This retrospective study was HIPAA compliant and approved by our Committee on Human Research. We identified all patients in our institutional prostate cancer database (1996 onward) who underwent endorectal MR imaging and MR spectroscopic imaging before radiotherapy for biopsy-proven prostate cancer and again at least 2 years after radiotherapy (n = 124). Two radiologists recorded the presence, location, and size of unequivocal dominant tumor on pre- and postradiotherapy scans. Recurrent tumor was considered to be at the same location as the baseline tumor if at least 50% of the tumor location overlapped. Clinical and biopsy data were collected from all patients.
Nine patients had unequivocal dominant tumor on both pre- and postradiotherapy imaging, with mean pre- and postradiotherapy dominant tumor diameters of 1.8 cm (range, 1-2.2) and 1.9 cm (range, 1.4-2.6), respectively. The median follow-up interval was 7.3 years (range, 2.7-10.8). Dominant recurrent tumor was at the same location as dominant baseline tumor in 8 of 9 patients (89%).
Local recurrence of prostate cancer after radiation usually occurs at the same site as the dominant primary tumor at baseline, suggesting supplementary focal therapy aimed at enhancing local tumor control would be a rational addition to management.

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    • "CTV HR to at least 145 Gy to ensure comparable tumor control as in clinical practice. Several studies have demonstrated that local recurrence of prostate cancer after radiotherapy usually occurs at the site of the primary tumor [37] [38] [39]. Although it is not clear if a dose escalation in low-risk prostate cancer patients is necessary, given the current high local control, our study shows that focal dose escalation is possible while reducing the dose to OAR. "
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