Treatment with radiolabelled somatostatin analogues is a promising new tool in the management of patients with inoperable or metastasized neuroendocrine tumours. Symptomatic improvement may occur with 177Lu-labelled somatostatin analogues that have been used for peptide receptor radionuclide therapy (PRRT). The results obtained with 177Lu-[DOTA0,Tyr3]octreotate (DOTATATE) are very encouraging in terms of tumour regression. Dosimetry studies with 177Lu-DOTATATE as well as the limited side effects with additional cycles of 177Lu-DOTATATE suggest that more cycles of 177Lu-DOTATATE can be safely given. Also, if kidney-protective agents are used, the side effects of this therapy are few and mild and less than those from the use of 90Y-[DOTA0,Tyr3]octreotide (DOTATOC). Besides objective tumour responses, the median progression-free survival is more than 40 months. The patients' self-assessed quality of life increases significantly after treatment with 177Lu-DOTATATE. Lastly, compared to historical controls, there is a benefit in overall survival of several years from the time of diagnosis in patients treated with 177Lu-DOTATATE. These findings compare favourably with the limited number of alternative therapeutic approaches. If more widespread use of PRRT can be guaranteed, such therapy may well become the therapy of first choice in patients with metastasized or inoperable neuroendocrine tumours.

Radiolabeled somatostatin analog therapy can stabilize tumor growth and can be very successful in further controlling severe hypoglycemia in malignant insulinomas. In our series, this eventually resulted in improved survival outside the hospital setting.

Pancreatic neuroendocrine tumors (NETs) are rare neoplasms for which surgery has almost the only potential for cure. When surgery is not possible because of tumor size and vascular involvement, neoadjuvant treatment with [ 177 Lu-DOTA 0 ,Tyr 3 ]octreotate ( 177 Luoctreotate) may be an option. Methods: We studied 29 Dutch patients with a pathology-proven nonfunctioning pancreatic NET treated with 177 Lu-octreotate. All patients had a borderline or unresectable pancreatic tumor (group 1) or oligometastatic disease (defined as #3 liver metastases) (group 2). Progression-free survival (PFS) was analyzed using the Kaplan-Meier method and Cox proportional hazards modeling. Results: After the treatment with 177 Luoctreotate, successful surgery was performed in 9 of 29 patients (31%). Six patients had a Whipple procedure, 2 patients had a pylorus-preserving pancreaticoduodenectomy, and 1 patient had a distal pancreatectomy and splenectomy. The median PFS was 69 mo for patients with successful surgery and 49 mo for the other patients. For comparison, the median PFS in 90 other patients with a nonfunctioning pancreatic NET with more than 3 liver metastases or other metastases was 25 mo. Conclusion: Neoadjuvant treatment with 177 Lu-octreotate is a valuable option for patients with initially unresectable pancreatic NETs.

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The primary treatment of gastroenteropancreatic neuroendocrine tumors (GEPNETs) is surgery with curative intent or debulking of the tumor mass. In case of metastatic disease, cytoreductive options are limited. A relatively new therapeutic modality, peptide receptor radionuclide therapy (PRRT) with radiolabeled somatostatin analogs, is currently available in a number of mostly European centers. Complete and partial responses obtained after treatment with [⁹⁰Y-DOTA⁰,Tyr³]octreotide are in the same range as after treatment with [¹⁷⁷Lu-DOTA⁰,Tyr³]octreotate (i.e. 10–30%). However, significant nephrotoxicity has been observed after treatment with [⁹⁰Y-DOTA⁰,Tyr³]octreotide. Options to improve PRRT may include combinations of radioactive labeled somatostatin analogs, intra-arterial administration, and the use of radiosensitizing drugs combined with PRRT. Other therapeutic applications of PRRT may include additional therapy cycles in patients with progressive disease after benefit from initial therapy, PRRT in adjuvant or neoadjuvant setting, or PRRT combined with new targeted therapies, such as sunitinib or everolimus. Randomized clinical trials comparing PRRT with other treatment modalities, or comparing various radioactive labeled somatostatin analogs should be undertaken to determine the best treatment options and treatment sequelae for patients with GEPNETs.

Response Evaluation Criteria In Solid Tumors (RECIST) (unidimensional), Southwest Oncology Group (SWOG) solid tumor response criteria (bidimensional), and their modified variants are commonly used in the tumor response assessment after treatment of gastroenteropancreatic and thoracic neuroendocrine tumors (NETs). In the current study, RECIST, SWOG criteria, modified RECIST (mRECIST), and modified SWOG (mSWOG) criteria were compared in patients with NETs treated with [ 177 Lu-DOTA 0 ,Tyr 3 ]octreotate ( 177 Luoctreotate). Methods: Two-hundred sixty-eight Dutch patients with NETs who had been treated with 177 Lu-octreotate between January 2000 and April 2007 were studied. CT or MR imaging scans were analyzed using RECIST, SWOG criteria, mRECIST, and mSWOG criteria (including the tumor response class minor response [decrease of 13%-30% for mRECIST and 25%-50% for mSWOG]). The outcomes were correlated with progression-free survival (PFS) and overall survival (OS). Results: Eleven patients had an unknown tumor response and were excluded. The rates of objective response (OR) (complete response 1 partial response [1minor response for mRECIST/mSWOG]), stable disease, and progressive disease (PD) were 28%, 49%, and 24%, respectively, according to RECIST; 25%, 49%, and 26%, respectively, according to SWOG; 44%, 33%, and 24%, respectively, according to mRECIST; and 45%, 29%, and 26%, respectively, according to mSWOG. In patients who had OR, stable disease, or PD, the median PFS was 26-30, 27-34, and 8 mo, respectively, with any of the 4 response criteria. In patients who had OR, stable disease, or PD, the median OS was 55-57, 56-74, and 11-12 mo, respectively, with any of the 4 response criteria. Subanalyses for patients who had progression before treatment start were comparable. Conclusion: Patients with PD as treatment outcome had significantly shorter PFS and OS than patients with an OR or stable disease with all 4 scoring systems. PFS and OS were comparable for patients with tumor regression and stable disease. The addition of the response class minor response did not improve the correlation with PFS and OS. The 4 scoring systems gave comparable results in terms of PFS and OS per categorized outcome.

We have noted that bone lesions on CT respond differently from soft-tissue lesions to treatment with [ 177 Lu-DOTA 0 ,Tyr 3 ]octreotate ( 177 Lu-octreotate). We therefore compared the response of bone lesions with that of soft-tissue lesions to treatment with 177 Luoctreotate in patients with gastroenteropancreatic and bronchial neuroendocrine tumors (NETs). Methods: Forty-two patients with well-differentiated NETs who had bone metastases that were positive on [ 111 In-DTPA 0 ]octreotide somatostatin receptor scintigraphy (SRS) before treatment, and who had soft-tissue lesions, were studied. All patients had had a minimum of 1 follow-up CT scan. Lesions were scored on CT and bone lesions also on SRS before and after treatment. Tumor markers (chromogranin A and 5-hydroxyindoleacetic acid) before and after treatment were compared. Results: Because bone lesions were not visible on CT before treatment in 11 of 42 patients (26%), bone and softtissue lesions were evaluated in 31 patients. Whereas bone lesions increased in size, soft-tissue lesions decreased in size. The percentage change in bone and soft-tissue lesions was significantly different at all time points up to 12 mo of follow-up (P , 0.001). The intensity or number of bone lesions on SRS decreased after treatment in 19 of 23 patients (83%) in whom SRS after treatment was available. The tumor markers also decreased significantly after treatment. In 1 patient, bone lesions became visible on CT after treatment, mimicking progressive disease with "new" bone lesions, although there was an overall treatment response. Conclusion: In patients with NETs, the apparent increase in size of bone lesions or the appearance of new bone lesions on CT after treatment with 177 Lu-octreotate should be interpreted cautiously, as this finding may be therapy-related rather than indicative of tumor progression.

The mean serum calcium level decreased significantly after treatment with (177)Lu-octreotate, resulting in mild hypocalcaemia in about 20% of patients. We excluded several potential causes of this hypocalcaemia, so the cause remains unknown. Serum calcium levels should be monitored after peptide receptor radionuclide therapy, and calcium substitution therapy should be initiated if appropriate.