A systematic review of positron emission tomography (PET) and positron emission tomography/computed tomography (PET/CT) for the diagnosis of breast cancer recurrence.

BACKGROUND Breast cancer (BC) accounts for one-third of all cases of cancer in women in the UK. Current strategies for the detection of BC recurrence include computed tomography (CT), magnetic resonance imaging (MRI) and bone scintigraphy. Positron emission tomography (PET) and, more recently, positron emission tomography/computed tomography (PET/CT) are technologies that have been shown to have increasing relevance in the detection and management of BC recurrence. OBJECTIVE To review the accuracy of PET and PET/CT for the diagnosis of BC recurrence by assessing their value compared with current practice and compared with each other. DATA SOURCES MEDLINE and EMBASE were searched from inception to May 2009. STUDY SELECTION Studies were included if investigations used PET or PET/CT to diagnose BC recurrence in patients with a history of BC and if the reference standard used to define the true disease status was histological diagnosis and/or long-term clinical follow-up. Studies were excluded if a non-standard PET or PET/CT technology was used, investigations were conducted for screening or staging of primary breast cancer, there was an inadequate or undefined reference standard, or raw data for calculation of diagnostic accuracy were not available. STUDY APPRAISAL Quality assessment and data extraction were performed independently by two reviewers. Direct and indirect comparisons were made between PET and PET/CT and between these technologies and methods of conventional imaging, and meta-analyses were carried out. Analysis was conducted separately on patient- and lesion-based data. Subgroup analysis was conducted to investigate variation in the accuracy of PET in certain populations or contexts and sensitivity analysis was conducted to examine the reliability of the primary outcome measures. RESULTS Of the 28 studies included in the review, 25 presented patient-based data and 7 presented lesion-based data for PET and 5 presented patient-based data and 1 presented patient- and lesion-based data for PET/CT; 16 studies conducted direct comparisons with 12 comparing the accuracy of PET or PET/CT with conventional diagnostic tests and 4 with MRI. For patient-based data (direct comparison) PET had significantly higher sensitivity [89%, 95% confidence interval (CI) 83% to 93% vs 79%, 95% CI 72% to 85%, relative sensitivity 1.12, 95% CI 1.04 to 1.21, p = 0.005] and significantly higher specificity (93%, 95% CI 83% to 97% vs 83%, 95% CI 67% to 92%, relative specificity 1.12, 95% CI 1.01 to 1.24, p = 0.036) compared with conventional imaging tests (CITs)--test performance did not appear to vary according to the type of CIT tested. For patient-based data (direct comparison) PET/CT had significantly higher sensitivity compared with CT (95%, 95% CI 88% to 98% vs 80%, 95% CI 65% to 90%, relative sensitivity 1.19, 95% CI 1.03 to 1.37, p = 0.015), but the increase in specificity was not significant (89%, 95% CI 69% to 97% vs 77%, 95% CI 50% to 92%, relative specificity 1.15, 95% CI 0.95 to 1.41, p = 0.157). For patient-based data (direct comparison) PET/CT had significantly higher sensitivity compared with PET (96%, 95% CI 90% to 98% vs 85%, 95% CI 77% to 91%, relative sensitivity 1.11, 95% CI 1.03 to 1.18, p = 0.006), but the increase in specificity was not significant (89%, 95% CI 74% to 96% vs 82%, 95% CI 64% to 92%, relative specificity 1.08, 95% CI 0.94 to 1.20, p = 0.267). For patient-based data there were no significant differences in the sensitivity or specificity of PET when compared with MRI, and, in the one lesion based study, there was no significant differences in the sensitivity or specificity of PET/CT when compared with MRI. LIMITATIONS Studies reviewed were generally small and retrospective and this may have limited the generalisability of findings. Subgroup analysis was conducted on the whole set of studies investigating PET and was not restricted to comparative studies. Conventional imaging studies that were not compared with PET or PET/CT were excluded from the review. CONCLUSIONS Available evidence suggests that for the detection of BC recurrence PET, in addition to conventional imaging techniques, may generally offer improved diagnostic accuracy compared with current standard practice. However, uncertainty remains around its use as a replacement for, rather than an add-on to, existing imaging technologies. In addition, PET/CT appeared to show clear advantage over CT and PET alone for the diagnosis of BC recurrence. FUTURE WORK Future research should include: prospective studies with patient populations clearly defined with regard to their clinical presentation; a study of diagnostic accuracy of PET/CT compared with conventional imaging techniques; a study of PET/CT compared with whole-body MRI; studies investigating the possibility of using PET/CT as a replacement for rather than an addition to CITs; and using modelling of the impact of PET/CT on patient outcomes to inform the possibility of conducting large-scale intervention trials.