Response, survival, and long-term toxicity after therapy with the radiolabeled somatostatin analogue [90Y-DOTA]-TOC in metastasized neuroendocrine cancers

Management of patients with hepatic metastases from neuroendocrine tumors

Neuroendocrine tumors have a disposition toward metastasis to the liver. A range of treatment modalities for neuroendocrine liver metastases is available in the clinical arena, the indications for which depend on tumor characteristics such as patterns of metastasis, tumor grade, and anatomical origin. The complete surgical resection of liver deposits represents the only option with the intent to cure and is the gold standard approach, whereas cytoreductive resection (debulking) presents another surgical option aiming to ameliorate the symptoms and prolong survival. Liver transplantation is generally an accepted option for highly selected patients. For patients ineligible for radical surgery, liver-directed therapies-transarterial embolization/chemoembolization, selective internal radiotherapy, and local tumor ablation-present alternative strategies. Systemic therapies include peptide receptor radiotherapy, somatostatin analogues, cytotoxic chemotherapeutics, and novel molecularly targeted drugs. However, despite the variety of treatments available, there exists little evidence to guide optimal clinical practice with currently available data predominantly retrospective in nature. In this review, we discuss the diagnostic procedures that influence the trajectory of treatment of patients with neuroendocrine liver metastases before critically appraising the evidence pertaining to these therapeutic strategies.

Liver transplantation for metastatic liver malignancies

PURPOSE OF REVIEW

Liver transplantation is a validated treatment of primary hepatobiliary tumours. Over the last decade, a renewed interest for liver transplantation as a curative treatment of colorectal liver metastasis (CR-LM) and neuro-endocrine metastasis (NET-LM) has developed.

RECENT FINDINGS

The ELTR and UNOS analyses showed that liver transplantation may offer excellent disease-free survival (ranging from 30 to 77%) in case of NET-LM, on the condition that stringent selection criteria are implemented. The interest for liver transplantation in the treatment of CR-LM has been fostered by the Norwegian SECA study. Five-year A 5-year survival rate of 60% could be reached. Despite the high recurrence rate (90%), one-third of patients were disease free following pulmonary surgery for metastases.

SUMMARY

Liver transplantation will take a more prominent place in the therapeutic algorithm of CR-LM and NET-LM. Larger experiences are necessary to improve knowledge about tumour biology and to refine selection criteria. A multimodal approach adding neo and adjuvant medical treatment to the transplant procedure will be key to bring this oncologic transplant project into the clinical arena. The preserved liver function in these patients will allow a more deliberate access to split liver and living donation for these indications.

Peptide receptor radionuclide therapy for advanced neuroendocrine tumors

Peptide receptor radionuclide therapy (PRRT) consists of the systemic administration of a synthetic peptide, labeled with a suitable β-emitting radionuclide, able to irradiate tumors and their metastases via internalization through a specific receptor (usually somatostatin S2), over-expressed on the cell membrane. After almost 2 decades of experience, PRRT, with either (90)Y-octreotide or (177)Lu-octreotate, has established itself to be an efficient and effective therapeutic modality. As a treatment, it is relatively safe up to the known thresholds of absorbed and bio-effective isotope dosages and the renal and hematological toxicity profiles are acceptable if adequate protective measures are undertaken.

Peptide receptor radionuclide therapy in a patient with disabling non-functioning pituitary adenoma

Non-functioning pituitary adenoma (NFPA) with higher proliferation index (WHO II) are often a therapeutical challenge. Low somatostatin receptor expression in these tumors usually prevents a treatment with somatostatin analogs. In 1996, a 55-year-old patient was referred due to right-sided headache. A pituitary macroadenoma with infiltration into the right cavernous sinus was diagnosed. There was no visual field deficit and the clinical and biochemical work up was consistent with a NFPA. The patient underwent transsphenoidal surgery. Residual adenoma remained in the right cavernous sinus. Histologically, a null-cell adenoma with a high proliferation index was documented (MIB-1: 11.6%, WHO II). Somatostatin receptor autoradiography was performed in the surgical specimen showing a homogenous expression of sst2 receptors. Radiosurgery was completed with stable disease for 8 years. In 2004, the patient was diagnosed with an incomplete palsy of the right oculomotorius nerve and a significant increase in the volume of the adenoma in the right cavernous sinus. After a positive Octreoscan(®) the patient consented to an experimental therapy approach using Lutetium DOTATOC (3 × 200 mCi). The palsy of the oculomotorius nerve improved and remained stable until today (March 2013), the follow-up MRI scans demonstrated stable disease. This is the first case of a patient with a NFPA (WHO II) in whom PRRT successfully improved the local complications of the tumor for more than 8 years after ineffective surgery and gamma knife therapy. The determination of sst2 in vitro using autoradiography and in vivo by Octreoscan was instrumental to administer this therapy in a challenging situation.

Assessment of predictors of response and long-term survival of patients with neuroendocrine tumour treated with peptide receptor chemoradionuclide therapy (PRCRT)

PURPOSE

To review the response and outcomes of (177)Lu-DOTA-octreotate chemoradionuclide therapy (LuTate PRCRT) in patients with neuroendocrine tumour (NET) expressing high levels of somatostatin receptors with uncontrolled symptoms or disease progression.

METHODS

A total of 68 patients (39 men; 17 - 76 years of age) who had completed an induction course of at least three cycles of LuTate PRCRT between January 2006 and June 2010 were reviewed. Ten patients were treated for uncontrolled symptoms and 58 had disease progression despite conventional treatment. The majority had four induction LuTate cycles (median treatment duration 5 months and cumulative activity 31 GBq), and 63 patients had concomitant 5-FU radiosensitizing infusional chemotherapy. Factors predicting overall survival were assessed using the log-rank test and Cox proportional hazards regression.

RESULTS

Of those treated for uncontrolled symptoms, 70 % received benefit maintained for at least 6 months after treatment. Among patients with progressive disease 68 % showed stabilization or regression on CT, 67 % on molecular imaging and 56 % biochemically up to 12 months after treatment; 32 patients died. Overall survival rates at 2 and 5 year were 72.1 % and 52.1 %, respectively. Median overall survival was not estimable at a median follow-up of 60 months (range 5 - 86 months). Nonpancreatic primary sites, dominant liver metastases, lesion size <5 cm and the use of 5-FU chemotherapy were statistically significantly associated with objective response. A disseminated pattern and a high disease burden (whole-body retention index) were associated with an increased risk of death. Objective biochemical, molecular imaging and CT responses were all associated with longer overall survival.

CONCLUSION

A high proportion of patients with progressive NET or uncontrolled symptoms received therapeutic benefit from LuTate with concomitant 5-FU chemotherapy. The achievement of objective biochemical, molecular or CT responses within 12 months was associated with improved overall survival. Patients with a primary pancreatic site and larger lesions (>5 cm) appeared to have lower objective response rates and may need a more aggressive treatment approach.

Peptide receptor radionuclide therapy in patients with inoperable meningiomas: our experience and review of the literature

OBJECTIVE

Few studies describe peptide receptor radionuclide therapy (PRRT) using (90)Y- or (177)Lu-labeled peptides in patients with recurrent meningiomas. No clinical data about (111)In-Pentetreotide in such patients are available. We report on (111)In-Pentetreotide therapy in patients with inoperable meningiomas and review the literature about PRRT of meningiomas.

METHODS

We reviewed clinical records of 8 patients with meningioma/meningiomatosis showing high (111)In-Pentetreotide uptake on pretherapy scintigraphy who were treated with at least one cycle of (111)In-Pentetreotide. In 2 patients, a cocktail of (111)In-Pentetreotide and beta-emitting radiolabeled peptides had been administered.

RESULTS

No patient experienced acute toxicity, neurological or renal function impairment. Mild transient bone marrow toxicity was observed in 4 patients. Objective partial response was observed in 2 patients, stable disease in 5 and disease progression in one. There were no statistically significant correlations between objective response and patient age, tumor WHO grade, baseline Karnofsky performance score, (111)In-Pentetreotide tumoral uptake grade, tumor/nontumor ratio, disease state at baseline, and cumulative dose.

CONCLUSIONS

In consideration of its efficacy and the lack of significant toxicity, PRRT of meningiomas using (111)In-Pentetreotide could be proposed even nowadays when the use of (177)Lu- or (90)Y-labeled peptides seems unsafe, namely in patients with renal impairment/toxicity.

(131)I-MIBG therapy for malignant paraganglioma and phaeochromocytoma: systematic review and meta-analysis

BACKGROUND

(131)I-MIBG therapy can be used for palliative treatment of malignant paraganglioma and phaeochromocytoma. The main objective of this study was to perform a systematic review and meta-analysis assessing the effect of (131)I-MIBG therapy on tumour volume in patients with malignant paraganglioma/phaeochromocytoma.

METHODS

A literature search was performed in December 2012 to identify potentially relevant studies. Main outcomes were the pooled proportions of complete response, partial response and stable disease after radionuclide therapy. A meta-analysis was performed with an exact likelihood approach using a logistic regression with a random effect at the study level. Pooled proportions with 95% confidence intervals (CI) were reported.

RESULTS

Seventeen studies concerning a total of 243 patients with malignant paraganglioma/phaeochromocytoma were treated with (131)I-MIBG therapy. The mean follow-up ranged from 24 to 62 months. A meta-analysis of the effect of (131)I-MIBG therapy on tumour volume showed pooled proportions of complete response, partial response and stable disease of, respectively, 0·03 (95% CI: 0·06-0·15), 0·27 (95% CI: 0·19-0·37) and 0·52 (95% CI: 0·41-0·62) and for hormonal response 0·11 (95% CI: 0·05-0·22), 0·40 (95% CI: 0·28-0·53) and 0·21 (95% CI: 0·10-0·40), respectively. Separate analyses resulted in better results in hormonal response for patients with paraganglioma than for patients with phaeochromocytoma.

CONCLUSIONS

Data on the effects of (131)I-MIBG therapy on malignant paraganglioma/phaeochromocytoma suggest that stable disease concerning tumour volume and a partial hormonal response can be achieved in over 50% and 40% of patients, respectively, treated with (131)I-MIBG therapy. It cannot be ruled out that stable disease reflects not only the effect of MIBG therapy, but also (partly) the natural course of the disease.

Individualized dosimetry-based activity reduction of ⁹⁰Y-DOTATOC prevents severe and rapid kidney function deterioration from peptide receptor radionuclide therapy

PURPOSE

Assessment of kidney function evolution after (90)Y-DOTATOC peptide receptor radionuclide therapy (PRRT) with capped activity administration based on a 37-Gy threshold of biological effective dose (BED) to the kidney.

METHODS

In a prospective phase II study, patients with metastasized neuroendocrine tumours were evaluated for therapy using 185 MBq (111)In-pentetreotide with amino acid coinfusion. Planar whole-body images were acquired at four time-points after injection and kidney volumes were measured using CT/MRI. BED to the kidneys was estimated using an extended BED formula and biexponential renal clearance. Based on published BED dose-toxicity relationships, we allowed a maximal kidney BED of 37 Gy; if the calculated BED exceeded 37 Gy, treatment activity was reduced accordingly. Kidney function was assessed at baseline and at 18 months, predominantly using (51)Cr-EDTA. The rate of renal function decline was expressed as annual glomerular filtration rate loss (aGFRL).

RESULTS

Only 22 of 50 patients reached the 18-months time-point, with most missing patients having died due to disease progression. In the 22 patients who reached 18 months, no rapid kidney function deterioration was observed over the 18 months, aGFRL >33% was not seen, and only three patients showed an increase of one toxicity grade and one patient an increase of two grades. No significant correlations between kidney volume (p = 0.35), baseline GFR (p = 0.18), risk factors for renal function loss (p = 0.74) and aGFRL were observed. Among the 28 patients who did not reach 18 months, one developed grade 4 kidney toxicity at 15 months after PRRT.

CONCLUSION

Prospective dosimetry using a 37 Gy BED as the threshold for kidney toxicity is a good guide for (90)Y-DOTATOC PRRT and is associated with a low risk of rapid renal function deterioration and evolution to severe nephrotoxicity.

177 Lu-Dota-octreotate radionuclide therapy of advanced gastrointestinal neuroendocrine tumors: results from a phase II study

PURPOSE

We evaluated the activity and safety profile of (177)Lu-Dotatate peptide receptor radionuclide therapy (Lu-PRRT) in patients with advanced, well-differentiated (G1-G2) gastrointestinal neuroendocrine tumors (GI-NETs).

METHODS

Forty-three patients with radiological tumor progression at baseline and a positive Octreoscan® completed the treatment with Lu-PRRT, resulting in the cumulative activity of 18.5 or 27.8 GBq in five cycles. Total activity was scheduled on the basis of kidney function or bone marrow reserve.

RESULTS

Twenty-five (58 %) patients were treated with a "standard" Lu-PRRT full dosage (FD) of 25.7 GBq (range 22.2-27.8), while the remaining 18 patients (42 %) who, at enrolment, showed a higher probability of developing kidney or bone marrow toxicity received a reduced dosage (RD) of 18.4 GBq (range 14.4-20.4). According to SWOG criteria, the overall response was complete response (CR) in (7 %) cases and stable disease (SD) in 33 (77 %), with a disease control rate (DCR) of 84 %. Median response duration was 25 months (range 7-50). Median progression-free survival (PFS) was 36 months (95 % CI 24-nr), and median overall survival (OS) has not yet been reached. Remarkably, none of the patients, including those at a higher risk of toxicity, showed side-effects after either dosage of Lu-PRRT.

CONCLUSION

Lu-PRRT was shown to be an effective therapeutic option in our patients with advanced progressive GI-NETs, showing an 84 % DCR (95 % CI 73-95) that lasted for 25 months and a PFS of 36 months. Both activities of 27.8 GBq and 18.5 GBq proved safe and effective in all patients, including those with a higher probability of developing kidney or bone marrow toxicity.

Cardiac manifestations of gastrointestinal carcinoid tumor

Carcinoid tumors are rare, slow-growing tumors found primarily in the GI tract. Carcinoid syndrome develops when vasoactive substances (particularly serotonin) released by carcinoid tumors gain access to the systemic circulation. Carcinoid heart disease develops in patients with carcinoid syndrome and is commonly associated with the development of right-sided valve dysfunction and signs of symptoms of right heart failure. Timely surgical intervention provides relief from symptoms and may improve survival. Management of these patients should be undertaken in a specialized center by a multidisciplinary team with appropriate expertise.

Peptide receptor radionuclide therapy using radiolabeled somatostatin analogs: focus on future developments

Peptide receptor radionuclide therapy (PRRT) has been shown to be an effective treatment for neuroendocrine tumors (NETs) if curative surgery is not an option. A majority of NETs abundantly express somatostatin receptors. Consequently, following administration of somatostatin (SST) analogs labeled with γ-emitting radionuclides, these tumors can be imaged for diagnosis, staging or follow-up purposes. Furthermore, when β-emitting radionuclides are used, radiolabeled peptides (radiopeptides) can also be used for the treatment for NET patients. Even though excellent results have been achieved with PRRT, complete responses are still rare, which means that there is room for improvement. In this review, we highlight some of the directions currently under investigation in pilot clinical studies or in preclinical development to achieve this goal. Although randomized clinical trials are still lacking, early studies have shown that tumor response might be improved by application of other radionuclides, such as α-emitters or radionuclide combinations, or by adjustment of radiopeptide administration routes. Individualized dosimetry and better insight into tumor and normal organ radiation doses may allow adjustment of the amount of administered activity per cycle or the number of treatment cycles, resulting in more personalized treatment schedules. Other options include the application of novel (radiolabeled) SST analogs with improved tumor uptake and radionuclide retention time, or a combination of PRRT with other systemic therapies, such as chemotherapy or treatment with radio sensitizers. Though promising directions appear to bring improvements of PRRT within reach, additional research (including randomized clinical trials) is needed to achieve such improvements.

Recommendations for management of patients with neuroendocrine liver metastases

Many management strategies exist for neuroendocrine liver metastases. These strategies range from surgery to ablation with various interventional radiology procedures, and include both regional and systemic therapy with diverse biological, cytotoxic, or targeted agents. A paucity of biological, molecular, and genomic information and an absence of data from rigorous trials limit the validity of many publications detailing management. This Review represents the views from an international conference, for which 15 expert working groups prepared evidence-based assessments addressing specific questions, and from which an independent jury derived final recommendations. The aim of the conference was to review the existing approaches to neuroendocrine liver metastases, assess the evidence on which management decisions were based, develop internationally acceptable recommendations for clinical practice (when evidence was available), and make recommendations for clinical and research endeavours. This report represents the final clinical statements and proposals for future research.

Synergism of peptide receptor-targeted Auger electron radiation therapy with anti-angiogenic compounds in a mouse model of neuroendocrine tumors

Background

Neuroendocrine tumors are well vascularized and express specific cell surface markers, such as somatostatin receptors and the glucagon-like peptide-1 receptor (GLP-1R). Using the Rip1Tag2 transgenic mouse model of pancreatic neuroendocrine tumors (pNET), we have investigated the potential benefit of a combination of anti-angiogenic treatment with targeted internal radiotherapy.

Methods

[Lys⁴⁰(Ahx-DTPA-¹¹¹In)NH₂]-exendin-4, a radiopeptide that selectively binds to GLP-1R expressed on insulinoma and other neuroendocrine tumor cells, was co-administered with oral vatalanib (an inhibitor of vascular endothelial growth factor receptors (VEGFR)) or imatinib (a c-kit/PDGFR inhibitor). The control groups included single-agent kinase inhibitor treatments and [Lys⁴⁰(Ahx-DTPA-^natIn)NH₂]-exendin-4 monotherapy. For biodistribution, Rip1Tag2 mice were pre-treated with oral vatalanib or imatinib for 0, 3, 5, or 7 days at a dose of 100 mg/kg. Subsequently, [Lys⁴⁰(Ahx-DTPA-¹¹¹In)NH₂]-exendin-4 was administered i.v., and the biodistribution was assessed after 4 h. For therapy, the mice were injected with 1.1 MBq [Lys⁴⁰(Ahx-DTPA-¹¹¹In)NH₂]-exendin-4 and treated with vatalanib or imatinib 100 mg/kg orally for another 7 days. Tumor volume, tumor cell apoptosis and proliferation, and microvessel density were quantified.

Results

Combination of [Lys⁴⁰(Ahx-DTPA-¹¹¹In)NH₂]-exendin-4 and vatalanib was significantly more effective than single treatments (p < 0.05) and reduced the tumor volume by 97% in the absence of organ damage. The pre-treatment of mice with vatalanib led to a reduction in the tumor uptake of [Lys⁴⁰(Ahx-DTPA-¹¹¹In)NH₂]-exendin-4, indicating that concomitant administration of vatalanib and the radiopeptide was the best approach. Imatinib did not show a synergistic effect with [Lys⁴⁰(Ahx-DTPA-¹¹¹In)NH₂]-exendin-4.

Conclusion

The combination of 1.1 MBq of [Lys⁴⁰(Ahx-DTPA-¹¹¹In)NH₂]-exendin-4 with 100 mg/kg vatalanib had the same effect on a neuroendocrine tumor as the injection of 28 MBq of the radiopeptide alone but without any apparent side effects, such as radiation damage of the kidneys.

Outcome of peptide receptor radionuclide therapy with 177Lu-octreotate in advanced grade 1/2 pancreatic neuroendocrine tumours

PURPOSE

The clinical benefit of peptide receptor radionuclide therapy (PRRT) in patients with pancreatic neuroendocrine tumours (pNET) has not yet been well described and defined in its full extent due to limited data in this tumour subgroup. This study was intended to obtain robust, comparative data on the outcome and toxicity of standardized PRRT with (177)Lu-octreotate in a well-characterized population of patients with advanced pNET of grade 1/2 (G1/2).

METHODS

We retrospectively analysed a cohort of 68 pNET patients with inoperable metastatic disease consecutively treated with (177)Lu-octreotate (four intended cycles at 3-monthly intervals; mean activity per cycle 8.0 GBq). Of these 68 patients, 46 (67.6 %) had documented morphological tumour progression during the 12 months before initiation of treatment, and PRRT was the first-line systemic therapy in 35 patients (51.5 %). Response was evaluated according to modified Southwest Oncology Group (SWOG) criteria and additionally with Response Criteria in Solid Tumors (RECIST) 1.1. Survival was analysed using Kaplan-Meier curves and Cox proportional hazards model for univariate and multivariate analyses. Toxicity was assessed by standard follow-up laboratory work-up including blood count, and liver and renal function, supplemented with serial (99m)Tc-DTPA clearance measurements.

RESULTS

The median follow-up period was 58 months (range 4 - 112). Reversible haematotoxicity (grade 3 or more) occurred in four patients (5.9 %). No significant nephrotoxicity (grade 3 or more) was observed. Treatment responses (SWOG criteria) consisted of a partial response in 41 patients (60.3 %), a minor response in 8 (11.8 %), stable disease in 9 (13.2 %), and progressive disease in 10 (14.7 %). Median progression-free survival (PFS) and overall survival (OS) were 34 (95 % CI 26 - 42) and 53 months (95 % CI 46 - 60), respectively. A G1 proliferation status was associated with longer PFS (p = 0.04) and OS (p = 0.044) in the multivariate analysis. Variables linked to impaired OS, on the other hand, were a reduced performance status (Karnofsky score ≤ 70 %, p = 0.007), a high hepatic tumour burden (≥ 25 % liver volume, p = 0.017), and an elevated plasma level of neuron-specific enolase (NSE >15 ng/ml, p = 0.035).

CONCLUSION

The outstanding response rates and survival outcomes suggest that PRRT is highly effective in advanced G1/2 pNET when compared to data of other treatment modalities. Independent predictors of survival are the tumour proliferation index, the patient's performance status, tumour burden and baseline plasma NSE level.

Early over-expression of GRP receptors in prostatic carcinogenesis

BACKGROUND

The GRP receptor shows high over-expression in prostatic adenocarcinoma and high grade PIN, but low expression in normal prostate glands. This represents the molecular basis for GRP receptor imaging of prostate cancer with radioactive compounds. However, a focal, high density GRP receptor expression can be observed in hitherto uncharacterized prostate glands.

METHODS

GRP receptors were quantitatively measured with in vitro receptor autoradiography using ¹²⁵I-Tyr⁴ -bombesin in samples from 115 prostates. On successive tissue sections, ¹²⁵I-Tyr⁴ -bombesin autoradiography was compared with H&E staining and MIB-1 and 34βE12 immunohistochemistry.

RESULTS

On one hand, it was confirmed that GRP receptors were expressed in adenocarcinoma and high grade PIN in high density and high incidence (77% and 73%, respectively), but in normal prostate glands in low density and low frequency (18%). On the other hand, a novel and intriguing observation was the existence of focal non-invasive prostate glands with high GRP receptor density, characterized by low grade nuclear atypia and increased proliferation, compatible with lower grade PIN. There was a significant GRP receptor density gradient (P ≤ 0.005), increasing from normal prostate glands (mean relative optical density, ROD, of ¹²⁵I-Tyr⁴ -bombesin binding: 0.17) over atypical glands without increased MIB-1 labeling (0.28) and atypical glands with increased MIB-1 expression (0.44) to high grade PIN and adenocarcinoma (0.64 and 0.58, respectively).

CONCLUSIONS

GRP receptor over-expression may be a novel, specific marker of early prostatic neoplastic transformation, arising in low grade PIN, and progressively increasing during malignant progression. This should be considered when interpreting in vivo GRP receptor imaging in males.

Gastrointestinal neuroendocrine tumors (NETs): new diagnostic and therapeutic challenges

This paper summarizes the current understanding of the biology of somatostatin receptor (sst), role of immunotherapy in neuroendocrine tumor (NET), new agents for PPRT, and methods to assess response and clinical benefit in NET. One of the most interesting aspects of sst biology is the recent discovery of truncated variants of the sst5 receptor subtype with unique tissue distribution and response to somatostatin (SST). These truncated receptors are associated with bad patient prognosis, decreased response to SST analogs, and may be new targets for diagnoses and treatment. IFN remains a cost-effective agent, particularly in classic mid gut carcinoids, and there is interest to continue examining immunotherapy's in this disease. PRRT remains a key strategy for treatment and imaging. In addition to the classic agents, there are a series of new agents targeting other receptors such as the incretin receptors (GLP-1R; GIPR) and other G-protein coupled receptors with great potential. With regards to therapy monitoring, the most commonly used criteria are Response Criteria Evaluation in Solid Tumors (RECIST). However, for different reasons, these criteria are not very useful in NET. Incorporation of other criteria such as Choi as well as functional imaging assessment with PET would be of great interest in this area.

Hematological toxicity of combined 177Lu-octreotate radiopeptide chemotherapy of gastroenteropancreatic neuroendocrine tumors in long-term follow-up

BACKGROUND

The combination of radiopeptide therapy [peptide receptor radionuclide therapy (PRRT)] with radiosensitizing chemotherapy of gastroenteropancreatic neuroendocrine tumors (GEP NETs) may improve efficacy, but has the potential to increase myelotoxicity. In a prospective clinical study of GEP NET patients treated with (177)Lu-octreotate PRRT in combination with capecitabine and temozolomide, as a prelude to a planned Australasian Gastro-Intestinal Trials Group (AGITG) international randomized controlled trial, we characterized the incidence and degree of hematological toxicity.

MATERIALS AND METHODS

Well-differentiated progressive metastatic GEP NETs in 65 patients were treated with 4 cycles of 7.8 GBq (177)Lu-octreotate, 1,650 mg/m(2) capecitabine (n = 28) and 1,500 mg/m(2) capecitabine with 200 mg/m(2) temozolomide (n = 37), and monitored for hematological toxicity over a 5-year period.

RESULTS

Short-term, self-limited hematological toxicity grade 3/4 comprised anemia in 1 patient (3.5%) in the 28 patient-cohort of patients treated with (177)Lu-octreotate and capecitabine. One of these patients (3.5%) later developed significant anemia and one developed thrombocytopenia (3.5%) over a median follow-up of 60 months (SD 20). The incidence of short-term grade 3/4 reversible myelosuppression in 37 patients after (177)Lu-octreotate/capecitabine/temozolomide was zero. Long- term follow-up for a median of 36 months (SD 11) showed significant thrombocytopenia in 2.7% and neutropenia in 2.7% of the patients and anemia in 10.8% of the patients (n = 4). The 3-year median hemoglobin and platelet and neutrophil counts trended downwards, but remained within normal ranges. Two patients in this cohort developed myelodysplastic syndrome.

CONCLUSION

The modest reversible hematological toxicity of PRRT of GEP NETs is not significantly increased by the addition of radiosensitizing chemotherapy with capecitabine and temozolomide in combination with (177)Lu-octreotate, which has the potential to enhance the efficacy of radiopeptide therapy.

Does PRRT with standard activities of 177Lu-octreotate really achieve relevant somatostatin receptor saturation in target tumor lesions?: insights from intra-therapeutic receptor imaging in patients with metastatic gastroenteropancreatic neuroendocrine tumors

Background

Peptide receptor radionuclide therapy (PRRT) with ¹⁷⁷Lu-[DOTA⁰,Tyr³]octreotate (¹⁷⁷Lu-octreotate) is generally performed using a fixed activity of 7.4 GBq (200 mCi) per course bound to 180 to 300 μg of the peptide. While this single activity may lead to suboptimal radiation doses in neuroendocrine tumors (NET) with advanced or bulky disease, dose escalation has been withheld due to concerns on potential tumor somatostatin receptor saturation with reduced efficacy of the added activity. In vivo saturation effects during standard-dose PRRT based on quantification of pre- and intra-therapeutic ⁶⁸Ga-DOTATOC positron emission tomography (PET) imaging might guide potential dose escalation.

Methods

Five patients with metastatic NET of the pancreas underwent ⁶⁸Ga-DOTATOC PET/CT before and directly after standard-dose PRRT with ¹⁷⁷Lu-octreotate. In each patient, four target tumor lesions, normal liver parenchyma, and the spleen were evaluated and the ratios of SUV_max of the target lesions to liver (SUV_T/L) and spleen (SUV_T/S) were calculated; paired Student's t test was performed with p < 0.05 for pre-/intra-PRRT comparisons.

Results

The mean intra-therapeutic tumor SUV_max showed no significant change (per-lesion paired t test) compared to pretreatment values (-9.1%, p = 0.226). In contrast, the SUV_max of the normal liver parenchyma and spleen were significantly lower directly after infusion of 7.4 GBq ¹⁷⁷Lu-octreotate. Consequently, SUV_T/L and SUV_T/S increased significantly from pretreatment to intra-therapeutic examination: SUV_T/L (p < 0.001) from 2.8 ± 1.3 (1.3 to 5.8) to 4.7 ± 3.0 (2.1 to 12.7) and SUV_T/S (p < 0.001) from 1.2 ± 0.7 (0.4 to 3.0) to 3.5 ± 1.5 (1.6 to 7.9).

Conclusions

This small retrospective study provides preliminary evidence for the absence of relevant in vivo saturation of somatostatin receptor subtype 2 (sst2) in tumor lesions during PRRT with standard activities of ¹⁷⁷Lu-octreotate in contrast to normal tissue (liver, spleen) showing limited receptor capacity. After being confirmed by larger series, this observation will have significant implications for PRRT: (1) Higher activities of ¹⁷⁷Lu-octreotate might be considered feasible in patients with high tumor disease burden or clinical need for remission, and (2) striving to reduce the amount of peptide used in standard preparations of ¹⁷⁷Lu-octreotate appears futile.

Treatment of malignant pancreatic neuroendocrine neoplasms: middle-term (2-year) outcomes of a prospective observational multicentre study

BACKGROUND

Information on malignant pancreatic neuroendocrine neoplasms (pNENs) is mostly from retrospective studies in highly selected patients. The aim of this prospective, multicentre study was to assess treatment and outcomes of malignant pNENs in clinical practice.

PATIENTS AND METHODS

Consecutive patients with newly diagnosed, histologically-proven pNENs were included and followed-up for 2 years. Tumours were defined as malignant when nodal or distant metastases were present or invasion of extrapancreatic structures/organs was evident.

RESULTS

A total of 140 patients with malignant pNENs were included. Ninety-eight patients (70.0%) underwent a surgical resection (76 radical and 22 palliative). Other non-surgical treatments were used in 101 patients (72.1%): somatostatin analogues (n = 63), chemotherapy (n = 30), ablative treatments (n = 15) and peptide-receptor radionuclide therapy (n = 14). No relationship was observed between the 2010 WHO classification and type of treatment. A surgical resection was more often performed in incidentally detected tumours located in the pancreas body tail. Two-year progression-free survival was 63.8%: 82% after a radical resection, 44% after a palliative resection and 41% without a resection. A radical resection and Ki67 proliferative index >5% and >10% were the only significant prognostic determinants in multivariate analysis.

CONCLUSIONS

A radical resection is the cornerstone treatment of malignant pNENs and represents, together with Ki67 assessment, the most powerful prognostic factor for 2-year outcomes.

Accurate assessment of long-term nephrotoxicity after peptide receptor radionuclide therapy with (177)Lu-octreotate

PURPOSE

Renal radiation during peptide receptor radionuclide therapy (PRRT) may result in glomerular damage, a potential reduction of glomerular filtration rate (GFR) and ultimately lead to renal failure. While reported PRRT nephrotoxicity is limited to data derived from serum creatinine-allowing only approximate estimates of GFR-the aim of this study is to accurately determine PRRT-induced long-term changes of renal function and associated risk factors according to state-of-the-art GFR measurement.

METHODS

Nephrotoxicity was analysed using (99m)Tc-diethylenetriaminepentaacetic acid (DTPA) clearance data of 74 consecutive patients with gastroenteropancreatic neuroendocrine tumours (GEP NET) undergoing PRRT with (177)Lu-octreotate. The mean follow-up period was 21 months (range 12-50) with a median of five GFR measurements per patient. The change of GFR was analysed by linear curve fit. Potential risk factors including diabetes mellitus, arterial hypertension, previous chemotherapy, renal impairment at baseline and cumulative administered activity were analysed regarding potential impact on renal function loss. In addition, Common Terminology Criteria for Adverse Events (CTCAE) v3.0 were used to compare nephrotoxicity determined by (99m)Tc-DTPA clearance versus serum creatinine.

RESULTS

The alteration in GFR differed widely among the patients (mean -2.1 ± 13.1 ml/min/m(2) per year, relative yearly reduction -1.8 ± 18.9%). Fifteen patients (21%) experienced a mild (2-10 ml/min/m(2) per year) and 16 patients (22%) a significant (>10 ml/min/m(2) per year) decline of GFR following PRRT. However, 11 patients (15%) showed an increase of >10 ml/min/m(2) per year. Relevant nephrotoxicity according to CTCAE (grade ≥3) was observed in one patient (1.3%) with arterial hypertension and history of chemotherapy. Nephrotoxicity according to serum creatinine was discordant to that defined by GFR in 15% of the assessments and led to underestimation in 12% of patients. None of the investigated factors including cumulative administered activity contributed to the decline of renal function.

CONCLUSION

Serious nephrotoxicity after PRRT with (177)Lu-octreotate is rare (1.3%). However, slight renal impairment (GFR loss >2 ml/min/m(2) per year) can frequently (43%) be detected by (99m)Tc-DTPA clearance assessments. Cumulative administered activity of (177)Lu-octreotate is not a major determinant of renal impairment in our study.

Single institutional series of neuroendocrine tumors managed in the Australian Capital Territory

AIMS

Retrospective review of neuroendocrine tumors (NETs) treated within the Australian Capital Territory to describe the local epidemiology and assess prognostic clinicopathological factors.

METHODS

Patients with histologically proven non-pulmonary low to intermediate grade NETs were identified from our hospital clinical database. Data were analyzed according to epidemiological, clinical and histopathological characteristics.

RESULTS

Of the 107 included patients, the most common primary tumor site was jejunum/ileum (32%), followed by rectum (22%) and pancreas (11.2%). In total, 32% had distant metastases at presentation, most commonly in the liver. Most patients were symptomatic at diagnosis, while 22.4% of cases were found incidentally. Second malignancies, in particular of gastrointestinal origin, were diagnosed in 33.6%. Surgical debulking was the most common treatment (59.8%) while 18% had multimodality therapy. With a median follow-up of 25 months from diagnosis, about 78% of patients are still alive. Median time to first relapse was 15 months and the 5-year survival rate was 80% for NETs of jejunum/ileum. Univariate survival analysis revealed tumor location, high Ki67 index, raised plasma chromogranin A, and urine 5-hydroxyindoleacetic acid upon diagnosis to be associated with shorter 5-year survival.

CONCLUSION

The epidemiologic characteristics and long-term outcome in our series are comparable to other reported studies. This analysis presents some important prognostic factors which could be used for risk stratification in patients with NETs.

Somatostatin receptors: from signaling to clinical practice

Somatostatin is a peptide with a potent and broad antisecretory action, which makes it an invaluable drug target for the pharmacological management of pituitary adenomas and neuroendocrine tumors. Somatostatin receptors (SSTR1, 2A and B, 3, 4 and 5) belong to the G protein coupled receptor family and have a wide expression pattern in both normal tissues and solid tumors. Investigating the function of each SSTR in several tumor types has provided a wealth of information about the common but also distinct signaling cascades that suppress tumor cell proliferation, survival and angiogenesis. This provided the rationale for developing multireceptor-targeted somatostatin analogs and combination therapies with signaling-targeted agents such as inhibitors of the mammalian (or mechanistic) target of rapamycin (mTOR). The ability of SSTR to internalize and the development of rabiolabeled somatostatin analogs have improved the diagnosis and treatment of neuroendocrine tumors.

Rapid blood clearance and lack of long-term renal toxicity of 177Lu-DOTATATE enables shortening of renoprotective amino acid infusion

PURPOSE

The aim of the study was to investigate the feasibility of shortening the recommended 4-h renoprotective amino acid infusion in patients receiving peptide receptor chemoradionuclide therapy (PRCRT) using radiosensitizing 5-fluorouracil. We evaluated the clearance of radiopeptide from the blood, long-term nephrotoxicity in patients undergoing PRCRT with the conventional 4-h amino acid infusion and renal uptake in patients receiving an abbreviated infusion.

METHODS

The whole-blood clearance of (177)Lu-DOTA-octreotate (LuTate) was measured in 13 patients receiving PRCRT. A retrospective analysis of short-term and long-term changes in glomerular filtration rate (GFR) in 96 consecutive patients receiving a 4-h infusion was performed. Renal LuTate retention estimated using quantitative SPECT/CT in 22 cycles delivered with a 2.5-h amino acid infusion was compared with that in 72 cycles with the 4-h infusion.

RESULTS

LuTate demonstrated biexponential blood clearance with an initial clearance half-time of 21 min. Approximately 88 % of blood activity was cleared within 2 h. With the 4-h protocol, there was no significant change in GFR (1.2 ml/min mean increase from baseline; 95 % CI -6.9 to 4.4 ml/min) and no grade 3 or 4 nephrotoxicity at the end of induction PRCRT. The long-term decline in GFR after a median follow up of 22 months was 2.2 ml/min per year. There was no significant difference in the renal LuTate retention measured in patients receiving a 2.5-h amino acid infusion compared to those who had a 4-h infusion.

CONCLUSION

The greatest renal exposure to circulating radiopeptide occurs in the first 1 - 2 h after injection. This, combined with the safety of LuTate PRCRT, allows consideration of an abbreviated amino acid infusion, increasing patient convenience and reducing human resource allocation.

Advancements in pancreatic neuroendocrine tumors

Pancreatic neuroendocrine tumors (PanNETs) have increased in incidence in the USA over the last 20 years. Although PanNETs are often misconceived as being indolent tumors as they have a far more favorable prognosis over pancreatic adenocarcinoma, roughly 60-70% of patients have metastatic disease at the time of diagnosis due to presentation late in the disease process. While improvements in imaging modalities allow for early detection and better tumor localization, recent advancements in basic science, as well as surgical and medical management of PanNETs have further improved the prognosis. The mainstay of therapy for localized PanNETs is surgical intervention, which has become safer and is slowly shifting towards a more minimally invasive approach. However, the prognosis still remains relatively bleak for patients with unresectable disease. Fortunately, novel molecular targeted therapies, such as everolimus and sunitinib, have recently come into the limelight and have shown significant promise for the treatment of locally advanced and metastatic disease.

Kidney dosimetry in ¹⁷⁷Lu and ⁹⁰Y peptide receptor radionuclide therapy: influence of image timing, time-activity integration method, and risk factors

Kidney dosimetry in ¹⁷⁷Lu and ⁹⁰Y PRRT requires 3 to 6 whole-body/SPECT scans to extrapolate the peptide kinetics, and it is considered time and resource consuming. We investigated the most adequate timing for imaging and time-activity interpolating curve, as well as the performance of a simplified dosimetry, by means of just 1-2 scans. Finally the influence of risk factors and of the peptide (DOTATOC versus DOTATATE) is considered. 28 patients treated at first cycle with ¹⁷⁷Lu DOTATATE and 30 with ¹⁷⁷Lu DOTATOC underwent SPECT scans at 2 and 6 hours, 1, 2, and 3 days after the radiopharmaceutical injection. Dose was calculated with our simplified method, as well as the ones most used in the clinic, that is, trapezoids, monoexponential, and biexponential functions. The same was done skipping the 6 h and the 3 d points. We found that data should be collected until 100 h for ¹⁷⁷Lu therapy and 70 h for ⁹⁰Y therapy, otherwise the dose calculation is strongly influenced by the curve interpolating the data and should be carefully chosen. Risk factors (hypertension, diabetes) cause a rather statistically significant 20% increase in dose (t-test, P < 0.10), with DOTATATE affecting an increase of 25% compared to DOTATOC (t-test, P < 0.05).

Peptide receptor radionuclide therapy for neuroendocrine tumors in Germany: first results of a multi-institutional cancer registry

Peptide receptor radionuclide therapy is an effective treatment option for patients with well-differentiated somatostatin receptor-expressing neuroendocrine tumors. However, published data result mainly from retrospective monocentric studies. We initiated a multi-institutional, prospective, board-reviewed registry for patients treated with peptide receptor radionuclide therapy in Germany in 2009. In five centers, 297 patients were registered. Primary tumors were mainly derived from pancreas (117/297) and small intestine (80/297), whereas 56 were of unknown primary. Most tumors were well differentiated with median Ki67 proliferation rate of 5% (range 0.9-70%). Peptide receptor radionuclide therapy was performed using mainly yttrium-90 and/or lutetium-177 as radionuclides in 1-8 cycles. Mean overall survival was estimated at 213 months with follow-up between 1 and 230 months after initial diagnosis, and 87 months with follow-up between 1 and 92 months after start of peptide receptor radionuclide therapy. Median overall survival was not yet reached. Subgroup analysis demonstrated that best results were obtained in neuroendocrine tumors with proliferation rate below 20%. Our results indicate that peptide receptor radionuclide therapy is an effective treatment for well- and moderately differentiated neuroendocrine tumors irrespective of previous therapies and should be regarded as one of the primary treatment options for patients with somatostatin receptor-expressing neuroendocrine tumors.

The joint IAEA, EANM, and SNMMI practical guidance on peptide receptor radionuclide therapy (PRRNT) in neuroendocrine tumours

Peptide receptor radionuclide therapy (PRRNT) is a molecularly targeted radiation therapy involving the systemic administration of a radiolabelled peptide designed to target with high affinity and specificity receptors overexpressed on tumours. PRRNT employing the radiotagged somatostatin receptor agonists (90)Y-DOTATOC ([(90)Y-DOTA(0),Tyr(3)]-octreotide) or (177)Lu-DOTATATE ([(177)Lu-DOTA(0),Tyr(3),Thr(8)]-octreotide or [(177)Lu-DOTA(0),Tyr(3)]-octreotate) have been successfully used for the past 15 years to target metastatic or inoperable neuroendocrine tumours expressing the somatostatin receptor subtype 2. Accumulated evidence from clinical experience indicates that these tumours can be subjected to a high absorbed dose which leads to partial or complete objective responses in up to 30 % of treated patients. Survival analyses indicate that patients presenting with high tumour receptor expression at study entry and receiving (177)Lu-DOTATATE or (90)Y-DOTATOC treatment show significantly higher objective responses, leading to longer survival and improved quality of life. Side effects of PRRNT are typically seen in the kidneys and bone marrow. These, however, are usually mild provided adequate protective measures are undertaken. Despite the large body of evidence regarding efficacy and clinical safety, PRRNT is still considered an investigational treatment and its implementation must comply with national legislation, and ethical guidelines concerning human therapeutic investigations. This guidance was formulated based on recent literature and leading experts' opinions. It covers the rationale, indications and contraindications for PRRNT, assessment of treatment response and patient follow-up. This document is aimed at guiding nuclear medicine specialists in selecting likely candidates to receive PRRNT and to deliver the treatment in a safe and effective manner. This document is largely based on the book published through a joint international effort under the auspices of the Nuclear Medicine Section of the International Atomic Energy Agency.

A review of the use of somatostatin analogs in oncology

Somatostatin is a neuropeptide produced by paracrine cells that are located throughout the gastrointestinal tract, lung, and pancreas, and is also found in various locations of the nervous system. It exerts neural control over many physiological functions including inhibition of gastrointestinal endocrine secretion through its receptors. Potent and biologically stable analogs of somatostatin have been developed. These somatostatin analogs show different efficacy on different receptors, and receptors are varyingly concentrated in specific tissues. Antitumor and antisecretory effects of somatostatin analogs in cancer have been shown in several in vivo and in vitro studies. However, these activities have not always yielded into clinically relevant patient outcome benefit. Somatostatin analogs are of clinical benefit in treating symptoms of ectopic hormone secretion (adrenocorticotropic hormone, growth hormone-releasing hormone) in lung cancer, without inducing a significant tumor response. They have also been shown to induce a statistically significant decrease in bone pain and increase in Karnofsky performance status in patients with metastatic prostate cancer. Somatostatin analogs alone or in combination with other agents have only limited antitumoral effect in breast cancer. In gastrointestinal cancers, studies have not shown an objective tumor response to somatostatin analogs except in endocrine tumors of the liver with symptomatic and biochemical improvement. In neuroendocrine tumors of the gastrointestinal system and pancreas, very high symptomatic and biochemical response rates have been achieved with somatostatin analogs. Antiproliferative activity has been clearly shown in metastatic midgut neuroendocrine tumors.

Systemic therapy for advanced pancreatic neuroendocrine tumors

Neuroendocrine tumors (NETs) occur throughout the body, and share similar histologic characteristics. However, it has become increasingly evident that pancreatic NETs tend to respond differently to therapeutic agents than do other NET subtypes. In most cases, systemic therapy has been more effective in NETs of pancreatic origin than in NETs arising from other locations. Traditional systemic treatment options for pancreatic NETs include somatostatin analogs or cytotoxic chemotherapy. Recently, the biologically targeted agents everolimus and sunitinib were approved for use in patients with metastatic disease. Novel agents, as well as novel drug combinations, are currently under investigation.

Systemic therapeutic options for carcinoid

"Carcinoids" are mostly slow-growing neuroendocrine neoplasms (NENs) with low proliferative activity. A wide range of therapeutic options with variable efficacy exist, including locoregional ablative strategies. Thereafter, some patients may not require medical therapy for years depending on the rate of progression or recurrence. However, the majority of patients require systemic treatment and therein lies the dilemma, since no antiproliferative agent is currently approved for carcinoids. Somatostatin analogs (SSAs), and to a lesser extent interferon-alpha, are standard therapy for carcinoids associated with the carcinoid syndrome. These drugs have some antiproliferative efficacy. SSAs rarely lead to tumor remission but may modestly prolong time to tumor progression. Chemotherapy is of limited value in carcinoids with low proliferation indices but may be useful in higher grade tumors. Peptide receptor-targeted radionuclide therapy may be of benefit and is mostly used after medical therapies fail. However, it is considered an investigational modality. More recently, targeted drugs such as mammalian target of rapamycin (mTOR) inhibitors and anti-angiogenics have been investigated. Objective remissions are rare. Their value remains to be rigorously elucidated. Increased efficacy requires a better understanding of the underlying tumor biology and identification of molecular pathological criteria to allow appropriate preselection of candidates for targeted therapies.

Recent progress in nanomedicine: therapeutic, diagnostic and theranostic applications

In recent years, the use of nanomedicine formulations for therapeutic and diagnostic applications has increased exponentially. Many different systems and strategies have been developed for drug targeting to pathological sites, as well as for visualizing and quantifying important (patho-) physiological processes. In addition, ever more efforts have been undertaken to combine diagnostic and therapeutic properties within a single nanomedicine formulation. These so-called nanotheranostics are able to provide valuable information on drug delivery, drug release and drug efficacy, and they are considered to be highly useful for personalizing nanomedicine-based (chemo-) therapeutic interventions.

Frequency and characterization of gastro-entero-pancreatic neuroendocrine tumor patients with high-grade of uptake at somatostatin receptor scintigraphy

Recent studies suggest that the somatostatin receptor scintigraphy (SRS) grade of uptake is a predictor of response to peptide receptor radionuclide therapy (PRRT). To identify and characterize patients with well-differentiated (WD) neuroendocrine neoplasm (NEN) displaying a high-grade uptake at SRS. Patients with WD-NEN, whose SRS films were available for review, were retrospectively included. SRS was reviewed by three independent readers and classified into four subgroups based on a modified Krenning's scale (mKS): no uptake (group-0), homogeneous grade 1-2 uptake (group-1), homogeneous grade 3-4 (group-2), and heterogeneous grade 1-4 (group-3). A simplified scale (sS) of SRS was also used to look for characteristics of patients with high-grade uptake. One hundred and six WD-NEN patients were enrolled. Group-0, group-1, group-2, and group-3 were found in 17, 8, 33, and 42% of cases respectively. High-grade uptake at sS (75% of cases) was correlated with older age, functioning NEN, high chromogranin-A level, and grade 1 (G1) NEN based on mitotic count. Based on the mKS or sS scales, no difference on survival was found. Thirty-three to seventy-five percent of metastatic NEN patients can be considered candidates for PRRT based on homogeneous or heterogeneous high-grade uptake. Functioning G1 NEN patients could be the best candidates for PRRT. Randomized trials are expected to confirm this result.

Targeting GRPR in urological cancers--from basic research to clinical application

Gastrin releasing peptide (GRP) is a regulatory peptide that acts through its receptor (GRPR) to regulate physiological functions in various organs. GRPR is overexpressed in neoplastic cells of most prostate cancers and some renal cell cancers and in the tumoral vessels of urinary tract cancers. Thus, targeting these tumours with specifically designed GRP analogues has potential clinical application. Potent and specific radioactive, cytotoxic or nonradioactive GRP analogues have been designed and tested in various animal tumour models with the aim of receptor targeting for tumour diagnosis or therapy. All three categories of compound were found suitable for tumour targeting in animal models. The cytotoxic and nonradioactive GRP analogues have not yet shown convincing tumour-reducing effects in human trials; however, the first clinical studies of radioactive GRP analogues--both agonists and antagonists--suggest promising opportunities for both diagnostic tumour imaging and radiotherapy of prostate and other GRPR-expressing cancers.

Peptide receptor radionuclide therapy with (90)Y-DOTATATE/(90)Y-DOTATOC in patients with progressive metastatic neuroendocrine tumours: assessment of response, survival and toxicity

Background:

Peptide receptor radionuclide therapy (PRRT) is an established treatment for patients with metastatic neuroendocrine tumours (NETs), although which factors are associated with an improved overall survival (OS) remains unclear. The primary aim of this study is to determine to what extent a radiological response to ⁹⁰Y-DOTATOC/⁹⁰Y-DOTATATE PRRT is associated with an improved OS. The association of biochemical and clinical response to OS were assessed as secondary outcome measures.

Methods:

A retrospective analysis was conducted on 57 patients: radiological response was classified using RECIST criteria, biochemical response was classified using WHO criteria and clinical response was assessed subjectively. Responses were recorded as positive response (PR), stable disease (SD) or progressive disease (PD), and survival analysed.

Results:

Radiological response was achieved in 71.5% (24.5% PR, 47% SD) and was associated with a greater OS (51 and 56 months, respectively), compared with PD (18 months). A biochemical or clinical response post PRRT were not associated with a statistically significant improvement in OS. However, when combined with radiological response a survival benefit was observed according to the number of outcomes (radiological, biochemical, clinical), in which a response was observed. Mild haematological toxicity was common, renal toxicity was rare.

Conclusion:

In patients with progressive metastatic NETs receiving ⁹⁰Y-DOTATOC/⁹⁰Y-DOTATATE PRRT, a radiological response with either a PR or a SD post therapy confers a significant OS benefit.