High somatostatin receptor expression and efficacy of somatostatin analogues in patients with metastatic Merkel cell carcinoma

BACKGROUND

Merkel cell carcinoma (MCC) is an aggressive, high-grade, cutaneous neuroendocrine tumour (NET). Agents blocking programmed death 1/programmed death ligand 1 have efficacy in metastatic MCC (mMCC), but half of patients do not derive durable benefit. Somatostatin analogues (SSAs) are commonly used to treat low- and moderate-grade NETs that express somatostatin receptors (SSTRs).

OBJECTIVES

To assess SSTR expression and the efficacy of SSAs in mMCC, a high-grade NET. Methods In this retrospective study of 40 patients with mMCC, SSTR expression was assessed radiologically by somatostatin receptor scintigraphy (SRS; n = 39) and/or immunohistochemically when feasible (n = 9). Nineteen patients (18 had SRS uptake in MCC tumours) were treated with SSA. Disease control was defined as progression-free survival (PFS) of ≥ 120 days after initiation of SSA.

RESULTS

Thirty-three of 39 patients (85%) had some degree (low 52%, moderate 23%, high 10%) of SRS uptake. Of 19 patients treated with SSA, seven had a response-evaluable target lesion; three of these seven patients (43%) experienced disease control, with a median PFS of 237 days (range 152-358). Twelve of 19 patients did not have a response-evaluable lesion due to antecedent radiation; five of these 12 (42%) experienced disease control (median PFS of 429 days, range 143-1757). The degree of SSTR expression (determined by SRS and/or immunohistochemistry) did not correlate significantly with the efficacy endpoints.

CONCLUSIONS

In contrast to other high-grade NETs, mMCC tumours appear frequently to express SSTRs. SSAs can lead to clinically meaningful disease control with minimal side-effects. Targeting of SSTRs using SSA or other novel approaches should be explored further for mMCC.

SPECT/CT bone scintigraphy to evaluate low back pain in young athletes: common and uncommon etiologies

Low back pain of various etiologies is a common clinical presentation in young athletes. In this article, we discuss the utility of SPECT/CT bone scintigraphy for the evaluation of low back pain in young athletes. The spectrum of lower spine lesions caused by sports injuries and identifiable on bone scan is presented along with strategies to avoid unnecessary irradiation of young patients. Also covered are pitfalls in diagnosis due to referred-pain phenomenon and normal skeletal variants specific to this age group.

Bone histology at autopsy and matched bone scintigraphy findings in patients with hormone refractory prostate cancer: the effect of bisphosphonate therapy on bone scintigraphy results

Bisphosphonates (BisP) are non-metabolized compounds with high bone affinity used in bone metastasis diagnosis and treatment. Currently, BisP are used to treat hypercalcemia of malignancy as well as to prevent, minimize, or delay skeletal morbidity. These compounds have a long half-life in bone. Thus long-term BisP treatment might saturate bone and interfere with a single-dose scanning agent used for bone scintigraphy when visualizing bone metastases. In an effort to answer this question, this study evaluated the concordance of histology and Technetium99 methylene diophosphonate (Tc99 MDP) bone scintigraphy in the diagnosis of bone metastases in prostate cancer patients. We assessed the concordance of findings between bone scintigraphy and histology using 188 bone biopsies from 11 autopsied patients who died with metastatic prostate cancer, 5 of whom were treated with pamidronate for 2 to 13 months before death. Overall agreement between histology and bone scintigraphy was 84%, 86% in non-pamidronate-treated patients and 82% in pamidronate-treated patients. Scintigraphic bone metastases without histological metastasis (false negatives = 12.7%) were observed in 24 anatomic locations; half of these were in one patient who had been treated with pamidronate and had no histological bone response to the carcinoma. There were only 4 sites where a positive bone scan was not associated with histologic metastasis (false positives = 2.21%). There was no statistical difference between the treated and non-treated group for concordance, specificity, sensitivity, positive and negative predictive values of bone scintigraphy and prevalence of histological abnormality. Long-term pamidronate treatment of prostate cancer bone metastases does not generally affect the ability to detect bone metastases with Tc99 MDP bone scintigraphy.

18fluorodeoxyglucose positron emission tomography to detect mediastinal or internal mammary metastases in breast cancer

PURPOSE

To determine the prevalence of suspected disease in the mediastinum and internal mammary (IM) node chain by 18fluorodeoxyglucose (FDG) positron emission tomography (PET), compared with conventional staging by computed tomography (CT) in patients with recurrent or metastatic breast cancer.

PATIENTS AND METHODS

We retrospectively evaluated intrathoracic lymph nodes using FDG PET and CT data in 73 consecutive patients with recurrent or metastatic breast cancer who had both CT and FDG PET within 30 days of each other. In reviews of CT scans, mediastinal nodes measuring 1 cm or greater in the short axis were considered positive. PET was considered positive when there were one or more mediastinal foci of FDG uptake greater than the mediastinal blood pool.

RESULTS

Overall, 40% of patients had abnormal mediastinal or IM FDG uptake consistent with metastases, compared with 23% of patients who had suspiciously enlarged mediastinal or IM nodes by CT. Both FDG PET and CT were positive in 22%. In the subset of 33 patients with assessable follow-up by CT or biopsy, the sensitivity, specificity, and accuracy for nodal disease was 85%, 90%, and 88%, respectively, by FDG PET; 54%, 85%, and 73%, respectively, by prospective interpretation of CT; and 50%, 83%, and 70%, respectively, by blinded observer interpretation of CT. Among patients suspected of having only locoregional disease recurrence (n = 33), 10 had unsuspected mediastinal or IM disease by FDG PET.

CONCLUSION

FDG PET may uncover disease in these nodal regions not recognized by conventional staging methods. Future prospective studies using histopathology for confirmation are needed to validate the preliminary findings of this retrospective study.

Functional imaging before pulmonary resection

The evaluation of patients before lung resections requires functional imaging. We review the current role of functional imaging in the preoperative evaluation of candidates for lung volume reduction surgery (LVRS) and lung cancer resection. Perfusion and ventilation lung scintigraphy methods as well as computed tomography techniques used to predict postoperative lung function are presented. The areas of current investigation are also described.

Lung cancer proliferation correlates with [F-18]fluorodeoxyglucose uptake by positron emission tomography

Tumor proliferation has prognostic value in resected early-stage non-small cell lung cancer (NSCLC). We evaluated whether [F-18]fluorodeoxyglucose (FDG) uptake of NSCLC correlates with tumor proliferation and, thus, could noninvasively grade NSCLCs (refining patient prognosis and therapy). Thirty-nine patients with potentially resectable NSCLC underwent whole-body FDG positron emission tomography (PET) 45 min after i.v. injection of 10 mCi of FDG. Tumor FDG uptake was quantitated with the maximum pixel standardized uptake value (maxSUV). The lesion diameter from computed tomography was used to correct the maxSUV for partial volume effects using recovery coefficients determined for the General Electric Advance PET scanner. Thirty-eight patients underwent complete surgical staging (bronchoscopy and mediastinoscopy, with or without thoracotomy). One stage IV patient by PET underwent bronchoscopic biopsy only. Immunohistochemistry for Ki-67 (proliferation index marker) was performed on all of the 39 NSCLC specimens (35 resections, 1 percutaneous, and 3 surgical biopsies). The specimens were reviewed for cellular differentiation (poor, moderate, well) and tumor type. Lesions ranged from 0.7 to 6.1 cm. The correlation found between uncorrected maxSUV and lesion size (Rho, 0.56; P = 0.0006) disappeared when applying the recovery coefficients (Rho, -0.035; P = 0.83). Ki-67 expression (percentage of positive cells) correlated strongly with FDG uptake (corrected maxSUV: Rho, 0.73; P < 0.0001). The correlation was stronger for stage I lesions (11 stage IA, 15 stage IB): Rho, 0.79; P < 0.0001) and strongest in stage IB (Rho, 0.83; P = 0.0019). A significant association (P < 0.0001) between tumor differentiation and corrected SUV was noted. FDG PET may be used to noninvasively assess NSCLC proliferation in vivo, identifying rapidly growing NSCLCs with poor prognosis that could benefit from preoperative chemotherapy.

Elimination of artifactual accumulation of FDG in PET imaging of colorectal cancer

BACKGROUND

Positron emission tomography (PET) with fluorine-18 labeled deoxyglucose (FDG) can detect tumor recurrences in surgical patients that are otherwise difficult to assess by CT, as well as distant metastases and small malignant nodes that are not identified by other imaging modalities. However, the evaluation of such malignancy is complicated by urinary and colonic concentrations of FDG. Methods and examples of the elimination of artifactual accumulation of FDG in PET imaging of the abdomen and pelvis are presented.

METHODS

Elimination of artifactual accumulation requires patient preparation that begins with cleansing of the colon using an isosmotic solution taken the evening prior to examination. Approximately 500 MBq of F-18 FDG is intravenously administered upon arrival at the PET facility and then the patient is hydrated. After administration of furosemide, a Foley catheter with a drainage bag is placed and the patient is then scanned. Just prior to scanning over the pelvis, normal saline is delivered retrogradely into the urinary bladder. At the end of scanning, the patient voids and repeated pelvic images are obtained.

RESULTS

These routines yield a clean scanning field. Lesions that will generally be missed because they are obscured by FDG accumulations along the colon or in the kidneys, ureters, or bladder are better visualized and identified with greater confidence. Artifacts that lead to misinterpretation also are reduced.

CONCLUSION

Elimination of artifactual accumulation of FDG in the colon and urinary system is essential if primary cancer, associated adenopathy, or subtle recurrences are to be evaluated in FDG PET imaging of the abdomen and pelvis.