Background: Multiple-gated acquisition scanning (MUGA) has traditionally been the
preferred imaging modality for baseline and serial assessment of left ventricular systolic
function in patients with cancer undergoing chemotherapy with potentially cardiotoxic
therapy. In recent years, cardiac magnetic resonance imaging (CMR) has emerged as
the preferred modality for the noninvasive assessment of left ventricular mass, volumes
and systolic function, and is currently considered the gold standard for assessment of
left ventricular ejection fraction (LVEF). However, it is not routinely used for the
assessment of LVEF in patients with cancer undergoing chemotherapy with potentially
cardiotoxic therapy. Comparisons between LVEFs measured by MUGA and CMR in
cancer patients and their implications on therapeutic decisions have not previously been
studied. The aim of our study was to assess the potential clinical impact of replacing
MUGA with the current gold standard modality of CMR for the assessment of LVEF in
patients with cancer.
Methods: The study population consisted of patients with cancer who underwent
cardiac evaluation from 2007 to 2014 at the University of Minnesota Medical Center with
both MUGA and CMR within 30 days of each other. Patient records were reviewed for
baseline demographic information, indication for imaging studies, co-morbidities and
medications. Clinical MUGA LVEF assessments performed by experienced nuclear
medicine technologists were used. To allow comparison to an ideal reference standard,
a single experienced investigator performed all the CMR LVEF analyses blinded to
MUGA and clinical data.
Results: 50 patients formed the final study cohort (mean age 56 ± 12 years, 54% male).
Using CMR as the reference standard, MUGA was found to systematically
underestimate LVEF by a mean of 2.6 percentage points (48.3% vs. 50.9%, p = 0.001).
The limits of agreement comparing MUGA and CMR LVEF were wide at -22.2 to 17.0
percentage points. Using the clinical practice guidelines of LVEF threshold for
anthracycline (≥50%) therapy, CMR reclassified 21 of 50 (42%) patients – 16 patients
that had MUGA LVEF <50% had a CMR LVEF ≥50% and 5 patients that had MUGA
LVEF ≥50% had CMR LVEF <50%. Similarly, using the accepted LVEF threshold for
trastuzumab (≥55%) therapy, CMR reclassified 12 of 50 (24%) patients – 10 patients
that had MUGA LVEF <55% had a CMR LVEF ≥55% and 2 patients that had MUGA
LVEF ≥55% had CMR LVEF <55%. On univariate analysis, the only significant predictor
of reclassification was a CMR measure of smaller left ventricular size as indicated by
lower left ventricular end-diastolic volume.
Conclusion: Replacing MUGA with CMR would have resulted in significant
reclassification for potential cancer therapy eligibility. Given the significant clinical impact
of reclassification and the increasing availability of the current gold standard modality,
routine use of CMR should be adopted for LVEF assessment in cancer patients.