Timing of fluorodeoxyglucose positron emission tomography maximum standardized uptake value for diagnosis of local recurrence of non-small cell lung cancer after stereotactic body radiation therapy.

INTRODUCTION: After treatment with stereotactic body radiation therapy (SBRT), local recurrence of non-small cell cancer (NSCLC) can be difficult to differentiate from radiation-induced changes. Maximum standardized uptake value (SUVmax), measured with 18-F-Fluorodeoxyglucose positron emission tomography (FDG-PET), can have false positives due to acute radiation inflammation. The primary study objective was to determine the utility of SUVmax > 5 to identify local recurrence later than 9 months after SBRT. METHOD: A retrospective review was performed of FDG-PET scans for suspicious CT findings after SBRT treatment of stage 1 NSCLC. SUVmax was measured including surrounding opacification. Outcome measures were local recurrence, progression free survival, and overall survival. Receiver operator curve analysis, sensitivity, specificity, and Kaplan-Meier analysis were performed. RESULTS: Of 118 patients treated, 42 patients had eligible FDG-PET scans. They received SBRT (48-60Gy in 3-8 fractions) for 49 NSCLC and had 101 follow-up PET scans. The median time to first PET scan was 9.3 months, and the median follow-up period was 22.4 months. Local recurrence was diagnosed in 12 patients, at a median of 16 months. Due to selection bias, the included patients had poorer outcomes than the entire cohort, with progression free survival (PFS) at 1, 2, and 3 years of 82.7%, 57.8%, and 45.8%; and overall survival of 97.9%, 79.9%, and 59.1%, respectively. Thirty FDG-PET scans were performed within 9 months, of which 17% were false positives. A total of 71 FDG-PET scans were performed beyond 9 months, and the median SUVmax was significantly higher for patients with local recurrence (7.48 vs. 2.14, P < .0001). SUVmax > 5 has a sensitivity of 91% (95% CI 62%-99.8%) and 100% (89.1%-100%). CONCLUSION: For local recurrence of NSCLC, SUVmax > 5 on FDG-PET scan has good sensitivity and specificity after 6 months, but is highest beyond 9 months after SBRT.

A pilot study of the utility of choline PET-CT in prostate cancer biochemical relapse following radical prostatectomy.

INTRODUCTION: To evaluate the detection rate of positive choline PET-CT and its clinical role in assisting with management decisions and the correlation between positive choline PET-CT and clinical/pathological parameters in prostate cancer patients with biochemical relapse following radical prostatectomy. METHODS: This was a longitudinal observational pilot study of 34 patients who received choline PET-CT scans with biochemical relapse after radical prostatectomy. Variables including peak PSA, PSA doubling time (DT), Gleason score, age, initial PSA at diagnosis, use of ADT prior to PET and initial clinical staging were statistically analysed to assess for independent predictive factors for positive PET findings. RESULTS: Choline PET-CT was positive in 38.2% of patients (13/34). The only statistically significant predictor for positive PET-CT was the use of ADT prior to PET-CT, with OR 18.7 (95% CI, 2.87-122.45), P < 0.01. Mean peak PSA for patients with positive PET-CT was 5.5 ± 4.8 ng/mL. Patients with positive PET-CT had a mean PSA DT of 5.1 ± 3.8 months and mean total Gleason of 7.6 ± 0.8. Although these variables were not statistically significant, they showed a tendency towards significance. At Receiver Operator Characteristics (ROC) analysis, a peak PSA value of 1.65 ng/mL and PSA DT of 4.4 months were determined to be the optimal cut-off values predicting positive PET-CT. CONCLUSION: Choline PET-CT has its potential as a diagnostic modality enabling the detection of occult prostate cancer recurrence and to differentiate localised disease from systemic disease thus guiding management. Use of ADT prior to PET-CT is a significant predictor of positive PET-CT. Patients with a short PSA DT, high-peak PSA and high Gleason score should also be considered for choline PET-CT.

Life-threatening hypokalaemia associated with ibuprofen-induced renal tubular acidosis.

Renal tubular acidosis is an underreported complication of ibuprofen misuse, and can result in life-threatening hypokalaemia. We describe four patients who presented with profound hypokalaemia and muscle weakness associated with excessive ibuprofen ingestion. Ibuprofen cessation and supportive management resulted in complete biochemical resolution within a few days. These cases remind practitioners about potential complications of unmonitored use of over-the-counter analgesics, including those with potential for misuse due to their codeine content.