Background:
Pheochromocytoma and
paraganglioma (PHEO/PGL) are rare
neuroendocrine tumors which may cause potentially life-threatening complications, with about a third of cases found to harbor specific gene mutations. Thus, early diagnosis, treatment, and meticulous monitoring are of utmost importance. Because of low incidence of
succinate dehydrogenase complex subunit A (SDHA)-related metastatic PHEO/PGL, currently there exists insufficient clinical information, especially with regards to its diagnostic and treatment characteristics. Methods: Ten patients with SDHA-related metastatic PHEO/PGL were followed-up prospectively and/or retrospectively between January 2010-July 2018. They underwent biochemical tests (n = 10), 123I-MIBG (n = 9) scintigraphy, and multiple whole-body positron emission tomography/computed tomography (PET/CT) scans with
68Ga-DOTATATE (n = 10),
18F-FDG (n = 10), and
18F-FDOPA (n = 6). Results: Our findings suggest that these
tumors can occur early and at extra-adrenal locations, behave aggressively, and have a tendency to develop metastatic disease within a short period of time. None of our patients had a family history of PHEO/PGL, making them appear sporadic. Nine out of 10 patients showed abnormal PHEO/PGL-specific
biochemical markers with predominantly noradrenergic and/or dopaminergic phenotype, suggesting their utility in diagnosing and monitoring the disease. Per patient detection rates of
68Ga-DOTATATE (n = 10/10),
18F-FDG (n = 10/10),
18F-FDOPA (n = 5/6) PET/CT, and 123I-MIBG (n = 7/9) scintigraphy were 100, 100, 83.33, and 77.77%, respectively. Five out of 7 123I-MIBG positive patients had minimal 123I-MIBG avidity or detected very few lesions compared to widespread metastatic disease on
18F-FDG PET/CT, implying that diagnosis and treatment with 123/131I-
MIBG is not a good option.
68Ga-DOTATATE PET/CT was found to be superior or equal to
18F-FDG PET/CT in 7 out of 10 patients and hence, is recommended for evaluation and follow-up of these patients. All 7 out of 7 patients who received conventional
therapies (
chemotherapy,
somatostatin analog
therapy, radiation therapy, 131I-
MIBG,
peptide receptor radionuclide therapy) in addition to surgery showed
disease progression. Conclusion: In our cohort of patients, SDHA-related metastatic PHEO/PGL followed a disease-course similar to that of SDHB-related metastatic PHEO/PGL, showing highly aggressive behavior, similar imaging and biochemical phenotypes, and suboptimal response to conventional
therapies. Therefore, we recommend careful surveillance of the affected patients and a search for effective
therapies.