The role of quantitative tumor burden based on [68 Ga]Ga-DOTA-NOC PET/CT in well-differentiated neuroendocrine tumors: beyond prognosis

PURPOSE

We aimed to elucidate the role of quantitative tumor burden based on PET/CT of somatostatin receptors in well-differentiated neuroendocrine tumors (NETs).

METHODS

This study enrolled patients with [68 Ga]Ga-DOTA-NOC PET/CT-positive advanced NETs who did not receive medical treatment prior to PET/CT. Tumor burden was calculated using methods based on the background threshold and relative fixed threshold values (30%, 40%, and 50%). The prognostic value of the measured tumor burden in reference to overall survival (OS) and progression-free survival (PFS) on treatment with octreotide long-acting repeatable (LAR) was assessed using Cox regression analysis, Harrell's C-index, and survival analysis. A classification and regression tree (CART) was used to determine the optimal threshold for tumor burden.

RESULTS

A total of 204 patients were included. Somatostatin receptor-expressing tumor volume (SRETV) and liver SRETV derived from a relative fixed threshold of 30% (SRETV30 and liver SRETV30) were statistically significantly associated with OS (C-index: 0.802 [95% confidence interval (CI), 0.658-0.946] and 0.806 [95% CI, 0.664-0.948], respectively). Extrahepatic tumor burden was not correlated with OS (hazard ratio: 0.617, 95% CI: 0.241-1.574, P = 0.312). Among 155 patients with non-functional NETs with a ki-67 index of ≤ 10%, those with a high SRETV30 (P = 0.016) or high liver SRETV30 (P = 0.014) showed statistically significantly worse PFS on treatment with octreotide LAR. Patients receiving a higher dose of octreotide LAR normalized by SRETV30 or liver SRETV30 (a normalized dose or a liver normalized dose) showed prolonged PFS on treatment with octreotide LAR and a prolonged OS.

CONCLUSION

Quantitative tumor burden based on [68 Ga]Ga-DOTA-NOC PET/CT was correlated with OS and PFS in patients with non-functional NETs with a ki-67 index of ≤ 10% who received octreotide LAR. Calculating normalized and liver normalized doses may help in selecting the starting dose of octreotide LAR.

Use of octreotide long acting repeatable (LAR) as second-line therapy in advanced neuroendocrine tumors in different clinical settings: an Italian Delphi survey

BACKGROUND

Somatostatin receptor ligands including octreotide LAR are first-line therapy in locally advanced or metastatic NETs that are nonresectable and well differentiated and are recommended as first-line therapy in functioning and in G1/low G2 nonfunctioning NETs. However, several questions remain that are not adequately addressed in current guidelines regarding its use in clinical scenarios in which the tumor progresses. These include use of nonconventional doses or schedules of octreotide LAR in tumors with hormonal symptoms or showing clinical-radiological progression, administration in combination with everolimus, peptide receptor radionuclide therapy, and chemotherapy, following first-line treatment with octreotide LAR.

METHODS

An expert panel was gathered to obtain consensus using Delphi methodology on a series of statements regarding further administration of octreotide LAR after its use in first-line therapy in these settings in patients who experience disease progression.

RESULTS

Consensus was reached for 8 of the 10 statements proposed in the above clinical scenarios; consensus was not achieved for two statements.

CONCLUSIONS

The present statements aim to fill current gaps in treatment guidelines by providing recommendations based on expert consensus in clinical settings in which patients progress following first-line therapy with octreotide LAR.

Patterns of Care Among Real-World Patients with Metastatic Neuroendocrine Tumors

BACKGROUND

Although recent pivotal trials (PROMID, CLARINET) have established somatostatin analogs (SSAs) as first-line agents for neuroendocrine tumors (NETs), their use in clinical practice is largely unknown. We aimed to understand real-world management and treatment of gastroenteropancreatic (GEP) NETs.

MATERIALS AND METHODS

Patients with metastatic GEP-NETs treated with SSAs, lanreotide depot or octreotide long-acting release (LAR), between January 1, 2015, and December 31, 2015, were identified from a U.S. claims database supplemented with chart review for a subset of patients. Descriptive statistics summarized patients' demographics, clinical characteristics, treatment patterns, and healthcare resource use. Univariate and multivariate comparisons were made across SSA groups.

RESULTS

Among 548 patients treated with an SSA for metastatic GEP-NET (lanreotide = 108; octreotide = 440), demographic and clinical characteristics were similar across groups, except more patients with pancreatic NETs were treated with lanreotide (38.7% vs. 6.3%, p < .01). More octreotide patients had a diagnosis of carcinoid syndrome compared with lanreotide patients (19.8% vs. 11.1%, p = .02). Approximately 1.1% of patients received lanreotide (>120 mg every 4 weeks [Q4W]) at a dose above label compared with 12.7% of octreotide patients (>30 mg Q4W; p < .01). At 1.5 years after SSA initiation, 85.7% (95% confidence interval, 74.3%-92.3%) were still on index SSA as reported by the physician. Variances between chart review and claims data were significant.

CONCLUSION

SSAs were common in first-line systemic intervention, but dose escalations and dosing deviations outside of label were noted. Variances between claims and chart review warrant additional research to compare methodologies. With an increasing focus on value-based care in oncology, it is critical to understand the use of, and outcomes with, these agents in community practices.

IMPLICATIONS FOR PRACTICE

The aim of this study was to enhance understanding of real-world management and treatment of metastatic neuroendocrine tumors (NETs), with particular focus on systemic therapy with a somatostatin analog (SSA). As per published guidelines, SSAs are common in first-line systemic intervention, but dose escalations and dosing deviations outside of the label are noted for symptom control. Nevertheless, oncologists must weigh the implications of the use of above-label dosing of SSAs to manage and treat patients with metastatic NET within a value-based care framework.

Octreotide LAR was useful for avoiding hypoglycemia in an elderly patient with insulinoma

An 80-year-old woman was admitted to our hospital with a hypoglycemia attack. She was diagnosed with insulinoma based on her high insulin level at the time of the hypoglycemia attack and the presence of a hypervascular tumor in her pancreas. The patient refused surgical treatment and octreotide was used to prevent hypoglycemia.It is known that octreotide suppresses the secretion of insulin from the pancreas; however, insulin secretion is not always suppressed in patients with insulinoma. Moreover, there is no particular protocol for the use of octreotide in the treatment of insulinoma.We examined the effect of octreotide in preventing hypoglycemia using CGM. The injection of octreotide (50 μg) at 21: 00 prevented hypoglycemia during the night.However the patient could not perform self-injection due to the sequelae of a cerebral infarction. We therefore chose to have her eat an extra meal at 11 pm.After a while the patient became exhausted by eating meals at night. We examined the effects of octreotide LAR using CGM, and it was found to prevent hypoglycemia for 4 weeks. The patient's QOL was improved by being released from a restriction that affected her daily life.

Diabetic ketoacidosis in a patient with acromegaly and central diabetes insipidus treated with octreotide long-acting release

A 43-year-old man was diagnosed with acromegaly due to pituitary GH-secreting macroadenoma, and underwent craniotomy surgery. After surgery, he was given octreotide long-acting release (LAR) to treat the residual tumor. Eighteen months later, he presented polydipsia and polyuria due to diabetic ketoacidosis (DKA) and central diabetes insipidus (CDI). His casual plasma glucose level was 570 mg/dL, his HbA1c was 14.9%, and his urine was strongly positive for ketone bodies. We discuss a causal relationship among DKA, CDI, and treatment with LAR in this case with residual GH-secreting tumor from the perspective of insulin secretion and resistance.

Competing risks of death in younger and older postmenopausal breast cancer patients

AIM: To show a new paradigm of simultaneously testing whether breast cancer therapies impact other causes of death.

METHODS: MA.14 allocated 667 postmenopausal women to 5 years of tamoxifen 20 mg/daily ± 2 years of octreotide 90 mg, given by depot intramuscular injections monthly. Event-free survival was the primary endpoint of MA.14; at median 7.9 years, the tamoxifen+octreotide and tamoxifen arms had similar event-free survival (P = 0.62). Overall survival was a secondary endpoint, and the two trial arms also had similar overall survival (P = 0.86). We used the median 9.8 years follow-up to examine by intention-to-treat, the multivariate time-to-breast cancer-specific (BrCa) and other cause (OC) mortality with log-normal survival analysis adjusted by treatment and stratification factors. We tested whether baseline factors including Insulin-like growth factor 1 (IGF1), IGF binding protein-3, C-peptide, body mass index, and 25-hydroxy vitamin D were associated with (1) all cause mortality, and if so and (2) cause-specific mortality. We also fit step-wise forward cause-specific adjusted models.

RESULTS: The analyses were performed on 329 patients allocated tamoxifen and 329 allocated tamoxifen+octreotide. The median age of MA.14 patients was 60.1 years: 447 (82%) < 70 years and 120 (18%) ≥ 70 years. There were 170 deaths: 106 (62.3%) BrCa; 55 (32.4%) OC, of which 24 were other malignancies, 31 other causes of death; 9 (5.3%) patients with unknown cause of death were excluded from competing risk assessments. BrCa and OC deaths were not significantly different by treatment arm (P = 0.40): tamoxifen patients experienced 50 BrCa and 32 OC deaths, while tamoxifen + octreotide patients experienced 56 BrCa and 23 OC deaths. Proportionately more deaths (P = 0.004) were from BrCa for patients < 70 years, where 70% of deaths were due to BrCa, compared to 54% for those ≥ 70 years of age. The proportion of deaths from OC increased with increasing body mass index (BMI) (P = 0.02). Higher pathologic T and N were associated with more BrCa deaths (P < 0.0001 and 0.002, respectively). The cumulative hazard plot for BrCa and OC mortality indicated the concurrent accrual of both types of death throughout follow-up, that is the existence of competing risks of mortality. MA.14 therapy did not impact mortality (P = 0.77). Three baseline patient and tumor characteristics were differentially associated with cause of death: older patients experienced more OC (P = 0.01) mortality; patients with T1 tumors and hormone receptor positive tumors had less BrCa mortality (respectively, P = 0.01, P = 0.06). Additionally, step-wise cause-specific models indicated that patients with node negative disease experienced less BrCa mortality (P = 0.002); there was weak evidence that, lower C-peptide (P = 0.08) was associated with less BrCa mortality, while higher BMI (P = 0.01) was associated with worse OC mortality.

CONCLUSION: We demonstrate here a new paradigm of simultaneous testing of therapeutics directed at multiple diseases for which postmenopausal women are concurrently at risk. Octreotide LAR did not significantly impact breast cancer or other cause mortality, although different baseline factors influenced type of death.