Target volume definition in high-risk prostate cancer patients using sentinel node SPECT/CT and ¹⁸ F-choline PET/CT

<p>Abstract</p> <p>Background</p> <p>To assess the influence of sentinel lymph nodes (SNs) SPECT/CT and ¹⁸ F-choline (¹⁸ F-FCH) PET/CT in radiotherapy (RT) treatment planning for prostate cancer patients with a high-risk for lymph node (LN) involvement.</p> <p>Methods</p> <p>Twenty high-risk prostate cancer patients underwent a pelvic SPECT acquisition following a transrectal ultrasound guided injection of ^99mTc-Nanocoll into the prostate. In all patients but one an ¹⁸ F-FCH PET/CT for RT treatment planning was performed. SPECT studies were coregistered with the respective abdominal CTs. Pelvic SNs localized on SPECT/CT and LN metastases detected by ¹⁸ F-FCH PET/CT were compared to standard pelvic clinical target volumes (CTV).</p> <p>Results</p> <p>A total of 104 pelvic SNs were identified on SPECT/CT (mean 5.2 SNs/patient; range 1–10). Twenty-seven SNs were located outside the standard pelvic CTV, 17 in the proximal common iliac and retroperitoneal regions above S1, 9 in the pararectal fat and 1 in the inguinal region. SPECT/CT succeeded to optimize the definition of the CTV and treatment plans in 6/20 patients due to the presence of pararectal SNs located outside the standard treatment volume. ¹⁸ F-FCH PET/CT identified abnormal tracer uptake in the iliac LN region in 2/19 patients. These abnormal LNs were negative on SPECT/CT suggesting a potential blockade of lymphatic drainage by metastatic LNs with a high tumour burden.</p> <p>Conclusions</p> <p>Multimodality imaging which combines SPECT/CT prostate lymphoscintigraphy and ¹⁸ F-FCH PET/CT identified SNs outside standard pelvic CTVs or highly suspicious pelvic LNs in 40% of high-risk prostate cancer patients, highlighting the potential impact of this approach in RT treatment planning.</p