Prevalence of hitherto unknown brain meningioma detected on (68)Ga-DOTATATE positron-emission tomography/computed tomography in patients with metastatic neuroendocrine tumor and exploring potential of (177)Lu-DOTATATE peptide receptor radionuclide therapy as single-shot treatment approach targeting both tumors

There is a relative paucity of data in the literature regarding the prevalence of meningiomas and their detection in the clinical setting of neuroendocrine tumors (NETs). The primary aim of this study was to study incidentally detected meningiomas (on (68)Ga-DOTATATE/ (18)F fluorodeoxyglucose positron-emission tomography/computed tomography [(18)F-FDG PET/CT]) in metastatic NET patients referred for peptide receptor radionuclide therapy (PRRT). The secondary aims of this study were to evaluate the response rate of these incidentally detected meningiomas following PRRT and determine progression-free survival (PFS) in this group of patients. This was a retrospective analysis of 500 metastatic/advanced NET patients who had undergone (68)Ga-DOTATATE PET/CT and (18)F-FDG PET/CT before PRRT workup. The case records were searched to identify cases of hitherto unknown meningiomas detected on PET images; subsequently, these patients underwent brain magnetic resonance imaging (MRI) for confirmation of diagnosis. Following (177)Lu-DOTATATE PRRT, posttreatment functional and structural imaging response evaluation of the meningiomas were undertaken by (68)Ga-DOTATATE PET/CT, MRI, or CT brain, respectively, along with clinical neurological evaluation. The patients were designated as responders and nonresponders based on predefined response assessment criteria. The PFS of these incidentally detected meningiomas following PRRT was estimated using the Kaplan–Meier product-limit method. Twelve NET patients were retrospectively identified with abnormal focal brain uptake on (68)Ga-DOTATATE PET/CT. Of these, meningiomas were finally diagnosed on brain MRI examination in six patients (M: F =3:3; age range: 30–66 years; and mean age: 45 years), with a prevalence of 1.2%. Standardized uptake value (SUVmax) of meningiomas on (68)Ga-DOTATATE and (18)F-FDG PET/CT ranged from 7.0 to 22.0 (average 17.0) and 10.19–13.70 (mean: 12.10), respectively, and lesion-to-normal brain parenchyma SUVmax ratio ranged from 140 to 400 (mean: 340) and 1.02–1.07 (mean: 1.04), respectively. Of six patients with incidentally detected meningiomas, one patient died within 1 month and five patients received (177)Lu-DOTATATE PRRT, the number of cycles ranging from two to six (average: 4) and cumulative therapeutic dose ranging from 13.28 to 29.97GBq (average dose: 19.86GBq). Follow-up in these patients ranged from 8 to 36 months (mean: 19.4 months) after the first dose of PRRT. Complete disappearance of neurological symptoms was found in two of five patients (40%), partial response in one of five (20%), and worsening of symptoms in two of five patients (40%). The overall “responder” and “nonresponder” of the meningiomas after PRRT were three patients (60%) and two patients (40%), respectively. Two patients (40%) died of advanced NET at the time of analysis of these data. The observed mean PFS of the meningioma lesions following PRRT was 26.25 months (95% confidence interval, 16.65–35.84 months). No major hematological and renal toxicity were documented in any of these patients. To conclude, (68)Ga-DOTATATE PET/CT imaging is an effective technique for the incidental identification of meningioma in NET patients. Considering the limited therapeutic options in the palliative setting of advanced or metastatic NET patients and morbidity associated with the therapeutic procedures, PRRT could be a promising targeted therapeutic approach for such cases of incidentally detected meningiomas, which is also helpful in stabilizing the disease process without any significant toxicity.