Technetium-99m-labeled lapachol as an imaging probe for breast tumor identification

OBJECTIVE

Breast cancer is a health problem worldwide with high incidence and mortality rates. It is well known that the development of more sensitive and specific diagnostic methods is of great importance since an early diagnosis is essential to successfully treat tumors. Lapachol is a natural compound, belonging to the naphthoquinone group that has been widely used in traditional medicine to treat various illnesses, including cancer. The aim of this study was to evaluate technetium-99m (^99mTc) labeled lapachol as an imaging probe for breast cancer identification.

METHODS

To achieve this purpose, lapachol was labeled with ^99mTc, radiochemical purity and in vitro stability were determined. Blood clearance, in healthy mice, and biodistribution, in 4T1 tumor-bearing mice, were also evaluated.

RESULTS

Lapachol was successfully labeled with ^99mTc, with high values of radiochemical yield (95.9±3.4%). In vitro stability showed that the radiolabeled complex remained stable for up to 24h, with values above 90% for both saline and plasma (95.6±3.6% and 96.4±1.7%, respectively). The radiolabeled complex decays in a biphasic manner, with a half-life of distribution and elimination equal to 3.3 and 50.0min, respectively. Biodistribution and scintigraphic images showed high uptake in organs of excretion (kidneys, liver, and intestine). It could be also noted that tumor uptake was higher than the muscle at all time points. Tumor-to-muscle ratio reaches ∼4.5 at 24h after administration.

CONCLUSION

These findings suggest that ^99mTc-lapachol can be a potential diagnostic agent for breast tumors.

The EANM practical guidelines for sentinel lymph node localisation in oral cavity squamous cell carcinoma

Purpose

Sentinel lymph node biopsy is an essential staging tool in patients with clinically localized oral cavity squamous cell carcinoma. The harvesting of a sentinel lymph node entails a sequence of procedures with participation of specialists in nuclear medicine, radiology, surgery, and pathology. The aim of this document is to provide guidelines for nuclear medicine physicians performing lymphoscintigraphy for sentinel lymph node detection in patients with early N0 oral cavity squamous cell carcinoma.

Methods

These practice guidelines were written and have been approved by the European Association of Nuclear Medicine (EANM) and the International Atomic Energy Agency (IAEA) to promote high-quality lymphoscintigraphy. The final result has been discussed by distinguished experts from the EANM Oncology Committee, and national nuclear medicine societies. The document has been endorsed by the Society of Nuclear Medicine and Molecular Imaging (SNMMI).

These guidelines, together with another two focused on Surgery and Pathology (and published in specialised journals), are part of the synergistic efforts developed in preparation for the “2018 Sentinel Node Biopsy in Head and Neck Consensus Conference”.

Conclusion

The present practice guidelines will help nuclear medicine practitioners play their essential role in providing high-quality lymphatic mapping for the care of early N0 oral cavity squamous cell carcinoma patients.

How to harmonize SUVs obtained by hybrid PET/CT scanners with and without point spread function correction

State of the art point-spread function (PSF) corrections implemented in positron emission tomography/computed tomography (PET/CT) reconstruction improved image quality and diagnostic performance but caused an increase in the standardized uptake value (SUV) compared to a conventional OSEM reconstruction system. The EANM suggested one produce two reconstructions, one optimised for maximum lesion detection and one for semi-quantitative analysis. In this work we investigated an alternative methodology, using a single reconstruction data set together with a post-reconstruction algorithm for SUV harmonization. Data acquisition was performed on a Siemens Biograph mCT system equipped with lutetium oxyorthosilicat crystals, PSF and time-of-flight algorithms and on a General Electric Discovery STE system equipped with BGO crystals. Both a EANM double reconstruction method and a dedicated post-reconstruction algorithm (marketed as EQ-filter) were tested to harmonize the quantitative values of the two PET/CT scanners. For phantom measurements we used a NEMA IQ phantom and a Jaszczak cylindrical phantom equipped with small spheres (lesion to background ratios of 8:1 and 4:1). Several different reconstruction settings were tested in order to provide a general methodology. Data obtained by phantom measurements were validated on seven oncologic patients who performed a one-bed extra acquisition on a different scanner. The evaluation regarded 39 small lesions (diameters: 0.3-2.6 cm) and was performed by two experienced nuclear medicine physicians. The SUV recoveries measured with the PSF reconstruction exceeded those obtained by the OSEM reconstruction with deviations ranging from 16% to 150%. These discrepancies resulted below 7% applying the optimized value of the EQ.filter or the double-reconstruction methods. For each reconstruction setting the optimal value of the EQ.filter was identified in order to minimize these discrepancies. Patient data, analyzed by Wilcoxon statistical test, confirmed and validated phantom measurements. EQ.filter can harmonize SUV values between different PET/CT scanners using a single reconstruction optimized to maximum lesion detectability. In this way, the second reconstruction proposed by EANM/EARL is avoided.

Sentinel lymph node biopsy in small papillary thyroid cancer. A review on novel surgical techniques

PURPOSE

Sentinel lymph node biopsy (SNB) in patients with papillary thyroid carcinoma (PTC) and negative for clinically neck lymph node metastatic involvement (N0) has emerged as a promising minimally invasive procedure to detect metastatic nodes.

METHODS

The MEDLINE database was searched via the PubMed interface on 10 January 2018 for the MeSH headings "sentinel lymph node biopsy" and "thyroid carcinoma".

RESULTS

Vital blue dye, radioisotope, and the combination of both techniques are used in PTC patients. These methods and the emerging role of SPECT/CT are discussed in this review. The sentinel lymph node (SLN) identification rates ranged from 0 to 100% for blue dye, 83 to 100% for radioisotopes, and 66 to 100% for the combination of both techniques, respectively.

CONCLUSIONS

SNB based on radioisotope technique with the use of intraoperative gamma-probe is an accurate and safe method that allows the highest SLN detection rate. There is sufficient evidence to propagate the increasing use of SNB procedure that has the potential to avoid prophylactic lymph node surgery in patients clinically N0.

Effect of Monacolin K and COQ10 supplementation in hypertensive and hypercholesterolemic subjects with metabolic syndrome

INTRODUCTION

Metabolic syndrome (MetS) is a world-wide epidemic disease with an increased risk of morbidity and mortality. Treatment strategies of MetS include pharmacologic and non-pharmacologic interventions and in this respect a relevant role has been shown for nutraceutical compounds (NCs). The aim of this study was to investigate the efficacy and safety of NCs incorporated with diet and lifestyle management versus diet alone, in lowering blood pressure (BP) values and improving lipid and glucose profile, in a group of hypertensives and hyper-cholesterolemic patients with MetS.

METHODS

104 subjects with MetS (mean age 57.4 ± 8.8 years, 51% males) without history of cardio-vascular (CV) diseases were enrolled in the study. 52 subjects were treated with a once-daily oral formulation of a NCs containing red yeast rice and coenzyme Q10 added to their diet for 2 months and were compared with the 52 patients following a diet program. Differences in BP, serum total cholesterol (TC), low- and high-density-lipoprotein cholesterol (LDLC and HDLC), triglycerides (TG) and glucose values were compared by analysis of variance.

RESULTS

A significant reduction of BP, TC, TG, LDLC and glucose levels was observed in both treatment groups. However, a greater reduction of systolic BP (-5.2 vs. -3.0 mmHg), diastolic BP (-4.9 vs. 2.9 mmHg), total cholesterol (-17.2%), LDLC (-21.8%), TG (-16.0%) and serum glucose (-3.4%) was observed in the treatment group relative to the control (p < 0.001 for all); HDLC remained unchanged (p = N.S.). Gender difference was not found in either group (p = N.S.).

CONCLUSIONS

In patients with MetS, NC supplementation was safe, well tolerated and effective in improving clinic BP, lipid and glucose profile.

99MTc-mibi Radio-guided Surgery in Primary Hyperparathyroidism: A Prospective Study of 128 Patients

Aims and study design

We investigated the role of an intraoperative gamma probe (IGP) technique in 128 patients with primary hyperparathyroidism (HPT). The patients were evaluated before surgery by 99mTcO4/MIBI scintigraphy and neck ultrasound and then operated on by the same surgical team. The IGP technique consisted of the injection of a low dose (37 MBq) of 99mTc-MIBI in the operating room shortly before the start of surgery. Quick parathyroid hormone (QPTH) was routinely measured during the operation.

Results

In 94/97 patients (96.9%) with a preoperative diagnosis of solitary parathyroid adenoma (PA) minimally invasive radioguided surgery (MIRS) was successfully performed; in the other 3/97 patients (3.1%) conversion to bilateral neck exploration (BNE) was required because of the intraoperative diagnosis of parathyroid carcinoma in two cases and multiglandular disease (MGD) in one. MIRS was successfully performed also in 23 patients who had undergone previous thyroid or parathyroid surgery. In 31 patients with a preoperative diagnosis of MGD (n = 5) or concomitant nodular goiter (n = 26) the IGP technique was used during a bilateral neck exploration. Among these patients IGP was useful in localizing an ectopic parathyroid gland in the thymus in one case of MGD and a PA located deep in the neck (n = 2) or ectopic at the carotid bifurcation (n = 1) in three cases with nodular goiter. However, in several other patients with nodular goiter it was difficult for the probe to distinguish intraoperatively between thyroid nodules and PA located close to the thyroid gland.

Conclusions

It can be concluded that a) in primary HPT patients with a high likelihood (according to scintigraphic and ultrasound findings) of being affected by a single PA and with a normal thyroid gland, the IGP technique appears useful in MIRS; b) a 99mTc-MIBI dose as low as 37 MBq appears to be adequate to perform MIRS; c) the measurement of QPTH is strongly recommended in HPT patients selected for MIRS to confirm the radicality of parathyroidectomy; d) MIRS can be useful also in HPT patients who underwent previous parathyroid or thyroid surgery to limit the surgical trauma of reoperation and minimize complications; e) with the exception of PAs located at ectopic sites or deep in the neck, the IGP technique does not seem to be recommendable in HPT patients with concomitant nodular goiter.

A Simplified Procedure for Continuous Intraoperative External Monitoring of Systemic Leakage during Isolated Limb Perfusion

Aims

Isolated limb perfusion (ILP) with high doses of an alkylating agent alone or in combination with tumor necrosis factor (TNF) in hyperthermic conditions (HAP) has been proposed for the treatment of locoregional tumors. A critical step in ILP/HAP is accurate monitoring of systemic leakage to prevent the toxic effects of chemotherapy, and in particular of TNF. Ten percent systemic leakage from the perfusion circuit is considered the maximum acceptable leakage. In this study we report our experience of a new leakage monitoring system.

Materials and methods

This new simplified procedure is based on the use of 99mTc-labeled soluble human serum albumin (HSA) and a hand-held gamma probe as detector. The procedure consists of the following steps: 1) A standardized 99mTc-HSA dose of 0.5 MBq/kg body weight is injected into the perfusion circuit before chemotherapy/TNF perfusion, and a hand-held gamma probe (IGP) is placed over the precordial area in a zone that was marked on the skin during a simulation test; 2) 48-72 hours before ILP/HAP a complete simulation test is performed with a 99mTc-HSA dose corresponding to 10% of the total dose calculated for the patient's body weight; 3) during the simulation test the maximum countrate zone on the precordial area is detected by IGP and marked on the patient's skin; 4) a 60-min curve of effective 99mTc-HSA radioactivity decay (physical and biological) is calculated and fitted; 5) to compare external counting with the effective circulating radioactivity, patient blood samples and circuit blood samples are taken every five minutes during ILP/HAP and measured by a laboratory gamma counter and very convenient thanks to the favorable characteristics of IGP. The placed in the operating room.

Results

External counting with a hand-held gamma probe was easy to perform time/activity curves obtained during simulation tests showed a regular and constant effective decay with a mean decay rate of 30% at 60 minutes compared to baseline values. The external measurements obtained by IGP proved to be well correlated with blood samples measured in vitro by a laboratory gamma counter. The results of this procedure, in particular the data of the simulation test for each patient, allowed us to correct the limit of 10% maximum leakage during ILP/HAP in accordance with the time/activity curve.

Conclusions

Although 99mTc-HSA has some unfavorable characteristics, it offers many advantages over 131I-HSA. The procedure proposed by us, which was based on the use of an IGP and 99mTc-HAS at a standardized dose of 0.5 MBq/kg body weight and on an individual simulation test for each patient performed 48 hours before ILP/HAP, proved to be simple and accurate in monitoring systemic leakage during ILP/HAP anticancer therapy.

The Role of Fluorine-18-Deoxyglucose (Fdg) Positron Emission Tomography (Pet) Whole Body Scan (Wbs) in the Staging and Follow-Up of Cancer Patients: Our First Experience

We report the results of FDG PET whole body scan in 75 cancer patients in whom tumor extent was defined by surgical, histological or cytological findings and clinical follow-up. Twenty-five had malignant lymphomas, 24 lung carcinomas, and 26 other types of solid tumors. Twenty-three patients were evaluated at disease onset, before therapy, and 37 at the moment of tumor recurrence; the remaining 15 patients were in complete remission after treatment and were taken as controls. Visual and quantitative PET results were compared with conventional imaging (US, CT scan and/or MRI, and Tc99m MDP bone scan).

In the 60 patients with active disease, PET as well as conventional imaging were able to locate the primary tumor in all 23 patients studied at disease onset. However, with regard to lymph node and distant metastases, PET provided the same information as conventional imaging in 31 cases (51.6%), but revealed further neoplastic foci in 29 cases (48.4%), 21 in lymph nodes and 8 at distant sites. The sensitivity of PET, in comparison with conventional imaging, was 100% versus 100% for the detection of the primary tumor, 97.6% versus 55.8% for the localization of node metastases, and 100% versus 55.5% for the visualization of distant metastases. The specificity, calculated in the group of 15 disease-free patients, was 100% for PET and 86.6% for conventional imaging. The therapeutic approach was modified in 12 patients (20%) on the basis of the PET results. Furthermore, in 14 cases (23.3%) with advanced disease, PET provided complete information on tumor spread, otherwise obtainable only by taking together the results of all other diagnostic procedures. Our data indicate a higher accuracy of FDG PET whole body scan compared to conventional imaging techniques in the evaluation of metastatic spread both at initial diagnosis and during follow-up, with an important impact on therapeutic decision-making. Moreover, by providing complete information on tumor spread in some cases, PET can become a profitable tool in terms of cost reduction.

Favorable Long Term Results in Patients with Small Differentiated Thyroid Cancer not Treated with Radioiodine

Data on a group of 110 patients with differentiated thyroid cancer not treated by radioiodine are reported. Most of them had intrathyroid (stage I) papillary or capsuled follicular cancer of less than 3 cm diameters. They all received thyroxine at TSH suppressive doses. The follow-up ranged between 4 and 25 years, mean 8.7. No patient died of tumor. Two very old patients died free of disease. Four recurrences occurred, within 8 years, all in patients over 45 years, all local or nodal, all papillary, 3 out of 4 after total thyroidectomy. This study shows that radioiodine therapy may be avoided and that lobectomy may be sufficient in patients under 45 years with small papillary or capsuled follicular cancer.

High Prevalence of Occult Papillary Thyroid Carcinoma in a Surgical Series for Benign Thyroid Disease

In a surgical series of 277 consecutive patients operated on the thyroid for benign diseases, a high prevalence rate (10.5%) of occult papillary carcinoma was found by means of an accurate histologic examination. Indications for surgery were euthyroid multinodular goiter in 25 patients, autonomously hyperfunctioning adenoma in 2 and Graves’ disease in 2 patients. Neoplastic foci were unilaterally found in 25 cases but multifocally in 6 and bilaterally in 4 cases: the diameters ranged from 2-10 mm. After operation (14 subtotal and 15 total thyroidectomies), all patients received TSH-suppressive doses of T4. At a mean follow-up of 5.6 years, neither local recurrences nor lymph node or distant metastases had occurred; no patient died of the tumor. In keeping with other surgical and autopsy series, the prevalence of occult thyroid carcinoma in a normal population is calculated to be about 5-10%, whereas it is known that the prevalence of clinically evident thyroid cancer is only 0.05%. This means that only 1-2% of occult carcinomas may evolve in an overt tumor during life. In view of such an epidemiologic difference and the favorable course of our patients, although the mean follow-up is rather short, we suggest that lobectomy plus T4 treatment may be considered an adequate therapeutic approach in patients with occult papillary thyroid carcinoma.

Distant Metastases in Differentiated Thyroid Cancer: Long-term Results of Radioiodine Treatment and Statistical Analysis of Prognostic Factors in 214 Patients

Long-term results and statistical analysis of prognostic factors in a series of 214 patients with distant metastases from differentiated thyroid cancer (DTC) are reported here. These 214 were part of a total series of 1457 patients with DTC referred to our center from 1967 to 1987. All patients underwent surgery and 131-I therapy and were treated with TSH suppressive doses of thyroid hormones. After a mean follow-up of 7.3 years including clinical, scintigraphic, radiological and laboratory investigations, 24.4% of patients were alive without disease, 36.5% alive with disease, 1.8% dead without disease and 37.3% dead with disease. One of the main factors influencing the survival in our series was 131-I uptake (RIU) by metastatic tissue. No case of complete remission of disease was observed among patients with nonfunctioning metastases. Another important factor was the site of metastases, patients with bone metastases having the worst prognosis. The patient's age at diagnosis represented another important factor for survival; patients over 40 years, particularly those over 60 years had a bad prognosis. A clear interrelation was found among the factors advanced age, nonfunctioning metastases and bone metastases. Patients with these last clinical features were considered to be at high risk and generally had a fatal outcome. Another significant prognostic factor revealed by univariate analysis was the histologic type. Patients with follicular tumor showed a poorer prognosis in comparison to papillary tumor. When multivariate analysis was applied, the factors age at diagnosis, site of metastases and RIU proved to have a significant influence on survival, but not the histologic type. Lastly, the relative rate of males was higher in the group of patients with metastases in comparison to the whole series of DTC patients. Despite this, the factor sex did not influence survival.

Sentinel Node Biopsy in Cutaneous Melanoma Patients: Technical and Clinical Aspects

The role of the patent blue dye (PBD) technique and intraoperative probe-guided lymphoscintigraphy (LS) in detecting the sentinel node (SN) was investigated in a group of 130 consecutive stage I cutaneous melanoma patients. The preoperative workup included high-resolution US scanning and LS performed 15–18 hours before surgery. On the basis of preoperative LS, in the group of examined patients a total of 143 lymphatic drainage basins were identified and surgically explored: 41.6% in the axilla, 52.8% in the groin, and 5.6% in the head/neck. A total of 228 SNs were intraoperatively detected and removed; 110 lymphatic basins contained histologically negative SNs, while 33 basins had metastatic SNs. The sensitivity for SN detection using PBD alone was 93%, while it was 100% when PBD was combined with intraoperative LS. Preoperative and intraoperative LS appears to be a highly sensitive technique for SN detection in cutaneous melanoma patients. Furthermore, in view of the limited skin incision when radioguided surgery is performed, SN biopsy could be feasible under local anesthesia.

Current Role of 111In-DTPA-Octreotide Scintigraphy in Diagnosis of Thymic Masses

Aims and background

Thymic tumors (thymomas and thymic carcinomas) represent 50% of all mediastinal tumors. Thymomas usually express high levels of somatostatin receptors, which enable in vivo imaging with 111In-DTPA-octreotide (OctreoScan®). The aim of this study was to further investigate the role of radionuclide techniques in the diagnosis, staging and follow-up of these tumors.

Methods

Eight patients (5 women, 3 men, age range 35–79 years; mean ± SD 56.1 ± 15.8 years) entered the study. In 4 patients, myasthenia gravis was the presenting symptom. 111In-DTPA-octreotide scan was performed within 3 weeks after contrast enhanced CT and/or MRI. Planar and tomographic images were acquired within 24 hours of the injection of 111 MBq OctreoScan. The scintigraphic results were defined in correlation with the histological findings.

Results

Histology revealed thymoma in 3 patients, thymic carcinoma in 1, insular carcinoma of presumably thymic origin in 1, thymic carcinoid in 1, and thymic hyperplasia in 2 patients. Two thymomas were at stage I, 1 thymoma and 1 thymic carcinoma at stage II, 1 insular carcinoma of presumably thymic origin at stage IV, and 1 thymic carcinoid at stage IV. OctreoScan consistently accumulated in primary and/or metastatic sites of thymic tumors while no radiotracer uptake was detected in the 2 patients with benign thymic hyperplasia. In 1 patient with a very large mediastinal mass (13 cm in largest diameter) and multiple metastatic deposits in the lungs, OctreoScan scintigraphy showed a large area of pathological uptake in the anterior mediastinum and a small area of focal uptake in the cervical-dorsal region of the right lung corresponding to a lymph node expressing somatostatin receptors.

Conclusions

OctreoScan is avidly taken up by thymic tumors, enabling the diagnosis of these tumors and a better evaluation of their extension. It does not accumulate in thymic hyperplasia, thus allowing the differential diagnosis between these 2 pathological conditions. In patients affected by myasthenia gravis, OctreoScan scintigraphy can play an important role in characterizing thymic masses.

Fludeoxyglucose F 18 PET/CT Assessment of Ovarian Cancer

Ovarian cancer is one of the most common gynecologic cancers and one of the leading causes of cancer death in women. It is often asymptomatic in early stages, and thus most patients are diagnosed when it is of advanced stage. For these reasons, the role of biomarkers and tomographic imaging is crucial. Fludeoxyglucose F 18 PET/CT is a useful imaging modality in different clinical settings of the disease, overcoming some limits of conventional imaging and influencing prognosis and therapeutic approaches. PET/MR imaging is an emerging modality, and its potential role remains to be explored.

Paclitaxel-loaded folate-coated long circulating and pH-sensitive liposomes as a potential drug delivery system: A biodistribution study

A range of antitumor agents for cancer treatment is available; however, they show low specificity, which often limit their use. Recently, we have reported the preparation of folate-coated long-circulating and pH-sensitive liposomes (SpHL-folate-PTX) loaded with paclitaxel (PTX), an effective drug for the treatment of solid tumors, including breast cancer. The purpose of this study was to prepare and characterize SpHL-PTX and SpHL-folate-PTX radiolabeled with technetium-99m (99mTc). Biodistribution studies and scintigraphic images were performed after intravenous administration of 99mTc-PTX, 99mTc-SpHL-PTX and 99mTc-SpHL-folate-PTX into healthy and tumor-bearing mice. High radiochemical purity (>98%) and in vitro stability (>90%) were achieved for both liposome formulations. The pharmacokinetic properties of 99mTc-SpHL-DTPA-PTX and 99mTc-SpHL-folate-DTPA-PTX decreased in a monophasic manner showing half-life of 400.1 and 541.8min, respectively. Scintigraphic images and biodistribution studies showed a significant uptake in liver, spleen and kidneys, demonstrating these routes as way for excretion. At 8h post-injection, the liposomal tumor uptake was higher than 99mTc-PTX. Interesting, 4h after administration, the liposome folate coated showed higher tumor-to-muscle ratio than 99mTc-SpHL-DTPA-PTX and 99mTc-PTX. In conclusion, the liposomal systems, showed high tumor uptake by scintigraphic images, especially the 99mTc-SpHL-folate-DTPA-PTX that showed a sustained and higher tumor-to-muscle ratio than non-functionalized liposome, which indicate its feasibility as a PTX delivery system to folate positive tumors.

Minimally invasive radio-guided parathyroidectomy on a group of 452 primary hyperparathyroid patients

The aim of this study was to investigate the efficacy of minimally invasive radio-guided parathyroidectomy (MIRP) in primary hyperparathyroid (PHPT) patients. Patients, methods: 452 consecutive PHPT patients were evaluated. Inclusion criteria for MIRP were (a) evidence at scintigraphy of a solitary parathyroid adenoma (PA); (b) a clear sestamibi uptake in the PA; (c) the absence of concomitant thyroid nodules; (d) no history of familial HPT or MEN; (e) no history of previous neck irradiation. Intra-operative protocol consisted of the injection of a low 37 MBq sestamibi dose in the operating suite 10 min before surgery. A hand held 11-mm collimated gamma probe was used. Quick PTH (QPTH) was routinely measured. Results: 344 out of the 452 patients met the inclusion criteria, and MIRP was successfully performed in 321 of them (93.3%). No major intra-operative complication was recorded. MIRP required a mean operative time of 32 min, and a mean hospital stay of 1.2 d. The parathyroid to background ratio (P/B) calculated by the probe was well correlated with the P/B calculated by sestamibi SPECT (r = 0.91; p <0.01), while no significant correlation was found between the probe-calculated P/B and the P/B calculated at planar sestamibi scan. Conclusions: In our experience: a) an accurate preoperative localising imaging protocol based on planar and SPECT sestamibi scan, and neck US is effective in selecting PHPT patients for MIRP, b) the P/B calculated by sestamibi SPECT seems able to predict the probe-calculated P/B more accurately than the P/B calculated at planar scan, c) the low 37 MBq sestamibi dose protocol proved to be a safe and effective approach to perform MIRP.

pH-Sensitive, Long-Circulating Liposomes as an Alternative Tool to Deliver Doxorubicin into Tumors: a Feasibility Animal Study

PURPOSE

Therapeutic agents used in chemotherapy have low specificity leading to undesired severe side effects. Hence, the development of drug delivery systems that improve drug specificity, such as liposome moieties, is an alternative to overcome chemotherapy limitations and increase antitumor efficacy. In this study, the biodistribution profile evaluation of pH-sensitive long-circulating liposomes (SpHL) containing [^99mTc]DOX in 4T1 tumor-bearing BALB/c mice is described.

PROCEDURES

[^99mTc]DOX was radiolabeled by direct method. Liposomes were prepared and characterized. [^99mTc]DOX was encapsulated into liposomes by freezing and thawing. Circulation time for SpHL-[^99mTc]DOX was determined by measuring the blood activity from healthy animals. Biodistribution studies were carried out in tumor-bearing mice at 1, 4, and 24 h after injection.

RESULTS

Blood levels of the SpHL-[^99mTc]DOX declined in a biphasic manner, with an α half-life of 14.1 min and β half-life of 129.0 min. High uptake was achieved in the liver and spleen, due to the macrophages captured. Moreover, tumor uptake was higher than control tissue, resulting in high tumor-to-muscle ratios, indicating higher specificity for the tumor area.

CONCLUSION

[^99mTc]DOX was successfully encapsulated in liposomes. Biodistribution indicated high tumor-to-muscle ratios in breast tumor-bearing BALB/c mice. In summary, these results showed the higher accumulation of SpHL-[^99mTc]DOX in the tumor area, suggesting selective delivery of doxorubicin into tumor.

The role of radionuclide probes for monitoring anti-tumor drugs efficacy: A brief review

Despite recent advances in the development of new therapeutic agents and diagnostic imaging modalities, cancer is still one of the main causes of death worldwide. A better understanding of the molecular signature of cancer has promoted the development of a new generation of anti-cancer drugs and diagnostic agents that specifically target molecular components such as genes, ligands, receptors and signaling pathways. However, intrinsic heterogeneity of tumors has hampered the overall success of target therapies even among patients with similar tumor types but unpredictable different responses to therapy. In this sense, post-treatment response monitoring becomes indispensable and nuclear medicine imaging modalities could provide the tools for an early indication of therapeutic efficacy. Herein, we briefly discuss the current role of PET and SPECT imaging in monitoring cancer therapy together with an update on the current radiolabeled probes that are currently investigated for tumor therapy response assessment.