Everolimus-induced somatostatin receptor overexpression in a rectal neuroendocrine tumor patient may promote somatostatin receptor-guided radionuclide therapy (peptide receptor radiotherapy) as an additional treatment option

We present a case of Grade II, well-differentiated rectal neuroendocrine tumor in a 39-year-old patient. Following different sequential treatment modalities, the disease progressed both on metabolic (18F-fluorodeoxyglucose positron emission tomography-computed tomography [(18)F-FDG PET/CT]) and somatostatin receptor (SSTR)-imaging ((68)Ga-DOTA-Tyr3-octreotate [(68)Ga-DOTATATE] PET/CT), and the patient received three cycles of peptide receptor radiotherapy (PRRT). Two years later, upon new progression due to the appearance of metabolically active, (68)Ga-DOTATATE PET/CT-negative liver lesions, targeted treatment with everolimus was introduced. Further morphologic and metabolic progression occurred 4 months after everolimus initiation, however, this time liver lesions demonstrated increased SSTR-expression on(68)Ga-DOTATATE PET/CT. Thus, the patient became eligible for a second PRRT course.