Nuclear Medicine & Radiation Therapy

Background: We prospectively compared FLT-PET and FDG-PET in evaluating response to cetuximab and chemoradiotherapy for HNSCC.

Methods: Six patients with HNSCC received cetuximab followed by chemoradiotherapy. Patients had FLTand FDG-PET scans at baseline, after cetuximab, and 2 weeks into chemoradiotherapy. Changes in SUVmax on successive scans were compared to baseline. Results: After induction therapy, changes in SUVmax ranged from -2 to 32% for FLT-PET and -24 to 0% for FDGPET. After two weeks of chemoradiotherapy, changes in SUVmax ranged from -71 to 9% for FLT-PET and -80 to -7% for FDG-PET. One patient experienced consecutive increases in FLT uptake not detected by FDG-PET. No patient recurred at a median 14.6 months.

Conclusions: Functional imaging early during definitive therapy for HNSCC is feasible. Similar changes in FLT and FDG uptake are detected during chemoradiotherapy; however, distinct differences were seen after induction cetuximab therapy. Further follow-up will facilitate correlation of radiotracer uptake with clinical outcome.

Abstract Objectives: For bladder preservation, cisplatinum is widely used radiosensitizer with concurrent chemoradiation (CRT). We aimed to evaluate the safety profile and potential benefit of gemcitabine as a radiosenistizer in bladder preservation.

Patients and methods: During July 2006 to January 2007, consecutive 32 patients with T2-T4N0M0 bladder cancer underwent transurethral resection of bladder tumor (TURBT) followed by concurrent chemoradiation with weekly gemcitabine 100 mg/m2 . Conformal radiotherapy was given with a shrinking field technique. Complete response was defined as no visible tumor on cystoscopy and biopsy.

Results: Of total, 26 patients received a median of 7 (3–8) cycles of gemcitabine and median cumulative radiation dose of 65 Gy. Grade 3 hematologic toxicities seen were; neutropenia (3.8%) and thrombocytopenia (7.7%). Grade 3 non-hematologic toxicities were; diarrhea (19.2%), nausea/vomiting (7.7%) and cystitis (15.4%). Complete response was achieved in 18 patients (69.2% [95% CI: 60–89%]). At median follow up of 36 months, four patients had local recurrences (two superficial and two muscle invasive). The overall intact bladder and overall survival rates were 75.1% and 56.3%, respectively. Conclusion: CRT with weekly gemcitabine was found feasible and highly active in the treatment of muscle invasive bladder cancer, as the 3 year intact bladder survival rates were promising.

Surgically unresectable primary and metastatic liver tumors have been increasingly treated with Y-90 radioembolization. In preparation for Y-90 radioembolization therapy, a baseline angiogram and a Tc-99m MAA hepatic perfusion study simulating Y-90 microsphere infusion are routinely performed, followed by a 2nd angiogram in which the catheter is positioned in the same position as during the baseline angiography. However, radiotracer distribution on paired Tc-99m MAA hepatic perfusion imaging and post-therapy Y-90 bremsstrahlung imaging studies does not always match. The purpose of this study was to examine perfusion differences or mismatch which involve hepatic segment(s) and to identify underlying causes by correlating with angiography. 81 paired Tc-99m MAA hepatic perfusion imaging and post-therapy Y-90 bremsstrahlung imaging studies and corresponding angiograms were reviewed. 31 studies showed segmental perfusion differences (SPDs). SPDs were less frequently observed with infusion into the left hepatic artery (LHA) as compared to the proper (PHA) and right hepatic artery (RHA) (P<0.05). Significant associations were found with differences in catheter tip position between the two angiograms (P<0.001), catheter tip in proximity to an arterial bifurcation (P<0.01) or a small branch (P<0.01). Differences in catheter position, in combination with proximity to an arterial bifurcation or an arterial branch showed strong association with SPDs (P<0.001). In conclusion, when the catheter tip is in proximity to an arterial bifurcation or a branch, subtle differences in its position can alter microsphere perfusion or trajectory to the target vessels, which can be demonstrated by segmental perfusion mismatch on paired Tc-99m MAA hepatic perfusion imaging and posttherapy Y-90 bremsstrahlung imaging studies.

Objectives: The objective of the current review was to use published data to assess the role of [18F] fluorodeoxyglucose-positron emission tomography (FDG-PET) as a complementary modality to computedtomography (CT) in radiotherapy target volume delineation for head and neck cancer (HNC).

Methods: Studies were identified by searching PubMed electronic databases. Both prospective and retrospective studies were included. Information regarding the role of FDG-PET for radiotherapy target volume delineation for HNC was analyzed.

Results: FDG-PET is a promising tool for improving radiotherapy target volume delineation by defining a metabolically active biological target volume (BTV). The use of novel PET tracers representing properties such as hypoxia, protein synthesis and proliferation remain to be better characterized.

Conclusions: The role of FDG-PET for radiotherapy target volume delineation for patients with HNC is expanding and should be further evaluated in clinical trials.