Super bone scan

Impact of Tumor Burden on Quantitative [68Ga] DOTATOC Biodistribution

PURPOSE

As has been previously reported, the somatostatin receptor (SSTR) imaging agent [⁶⁸Ga]-labeled 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid-d-Phe(1)-Tyr(3)-octreotate ([⁶⁸Ga]DOTATATE) demonstrates lower uptake in normal organs in patients with a high neuroendocrine tumor (NET) burden. Given the higher SSTR affinity of [⁶⁸Ga] DOTATATE, we aimed to quantitatively investigate the biodistribution of [⁶⁸Ga]-labeled 1,4,7,10-tetraazacyclododecane-N,N',N″,N‴-tetraacetic acid-d-Phe(1)-Tyr(3)-octreotide ([⁶⁸Ga]DOTATOC) to determine a potential correlation between uptake in normal organs and NET burden.

PROCEDURES

Of the 44 included patients, 36/44 (82 %) patients demonstrated suspicious radiotracer uptake on [⁶⁸Ga] DOTATOC positron emission tomography (PET)/X-ray computed tomography (CT). Volumes of interest (VOIs) were defined for tumor lesions and normal organs (spleen, liver, kidneys, adrenals). Mean body weight corrected standardized uptake value (SUV_mean) for normal organs was assessed and was used to calculate the corresponding mean specific activity uptake (Upt: fraction of injected activity per kg of tissue). For the entire tumor burden, SUV_mean, maximum standardized uptake value (SUV_max), and the total mass (TBM) was calculated and the decay corrected tumor fractional uptake (TBU) was assessed. A Spearman's rank correlation coefficient was used to determine the correlations between normal organ uptake and tumor burden.

RESULTS

The median SUV_mean was 18.7 for the spleen (kidneys, 9.2; adrenals, 6.8; liver, 5.6). For tumor burden, the median values were SUV_mean 6.9, SUV_max 35.5, TBM 42.6 g, and TBU 1.2 %. With increasing volume of distribution, represented by lean body mass and body surface area (BSA), Upt decreased in kidneys, liver, and adrenal glands and SUV_mean increased in the spleen. Correlation improved only for both kidneys and adrenals when the influence of the tumor uptake on the activity available for organ uptake was taken into account by the factor 1/(1-TBU). TBU was neither predictive for SUV_mean nor for Upt in any of the organs. The distribution of organ Upt vs. BSA/(1-TBU) were not different for patients with minor TBU (<3 %) vs. higher TBU (>7 %), indicating that the correlations observed in the present study are explainable by the body size effect. High tumor mass and uptake mitigated against G1 NET.

CONCLUSIONS

There is no significant impact on normal organ biodistribution with increasing tumor burden on [⁶⁸Ga] DOTATOC PET/CT. Potential implications include increased normal organ dose with [¹⁷⁷Lu-DOTA]⁰-D-Phe¹-Tyr³-Octreotide and decreased absolute lesion detection with [⁶⁸Ga] DOTATOC in high NET burden.

Prolonged Hypocalcemia Following a Single Dose of Denosumab for Diffuse Bone Metastasis of Gastric Cancer after Total Gastrectomy

Hypocalcemia is a significant adverse effect of denosumab. We herein report a case of prolonged hypocalcemia in a patient with multiple risk factors for hypocalcemia, including gastrectomy, increased bone turnover, and a poor performance status. Hypocalcemia developed after denosumab treatment for diffuse bone metastasis of gastric cancer, despite oral supplementation with vitamin D and calcium. To avoid serious prolonged hypocalcemia, a thorough assessment of the bone calcium metabolism is required before initiating denosumab treatment.

Skeletal Metastases Presenting as Superscan on Technetium 99m Methylene Diphosphonate Whole Body Bone Scintigraphy in Different Type of Cancers: A 5-Year Retro-prospective Study

The purpose of the study is to find out the overall incidence of superscan among different type of cancers, causes of superscan and its relationship with other parameters such as age, sex, duration of disease, and serum alkaline phosphatase (ALP) levels. This was a retro-prospective study. Records of all previous bone scans and reported patients of superscan were re-evaluated retrospectively. Patients who were diagnosed as having superscan in the preceding 3 years with confirmed histopathological diagnosis were included in the retrospective group. In the prospective group, all the patients who were reported to have superscan appearance over the past 2 years of prospective period were included. Total of 6027 bone scans were examined in a 5-year period and out of which 80 cases were diagnosed as superscan. The overall incidence of superscan in different type of cancers was 1.3% (80/6027). Prostate cancer (46/80) was the most common cause of superscan appearance followed by breast cancer (10/80). Out of 6027 patients referred for bone scan, 307 patients had prostate cancer on histopathological examination. Out of 307 patients with prostate cancer, 46 had superscan appearance. Incidence of superscan in prostate cancer was 14.98% (46/307), and 71.73% (33/46) prostate cancer patients with superscan had Gleason score of 8 and above 8 with mean serum prostate-specific antigen level was 178.42 ng/ml in symptomatic patients and 122 ng/ml in asymptomatic patients. Out of all patients with superscan, 71 patients (88.7%) had elevated serum ALP levels. Overall incidence of superscan in our study was 1.3% in different type of cancer patients, and the most common cause of superscan appearance was prostate cancer. Incidence of superscan appearance in prostatic cancer patients was 14.98%.

Metabolic super scan in F-FDG PET/CT imaging

A 50-yr-old man presented with intermittent hemoptysis and was diagnosed small cell lung cancer. (18)F-FDG PET/CT for staging demonstrated extensive hypermetabolic lesions throughout the skeleton and liver. Interestingly, skeletal muscles of limbs, mediastinum, bowel, and especially brain showed very low FDG uptake. Because of some characteristics in common with super scan on skeletal scintigraphy, this case could be considered as 'metabolic super scan'.

Super bone scan due to bone marrow metastases appearing 19 years after surgery for early gastric cancer--a case report

A 54 year old man presenting a so-called super bone scan is reported. The patient had a past history of subtotal gastrectomy due to early gastric cancer 19 years previously. Laboratory data indicated microcytic anemia and high serum alkaline phosphatase. Both the serum calcium and phosphate levels were within normal ranges. In spite of extensive examination for a primary malignant lesion in the organs including the remaining stomach, no solid tumors were identified. Pathological examinations revealed that the tumor cells in the biopsy specimen from the lumbar spine were almost identical to those in the gastric cancer excised 19 years previously. We considered that micrometastases in the bone marrow existed at the time of the initial surgery for gastric cancer and reappeared 19 years later showing super bone scan.

Sub-super bone scan caused by bone marrow involvement of prostate cancer

A 67-year-old man presented with malaise and marked anemia. A diagnostic workup revealed severe pancytopenia on a complete blood count and diffuse sclerotic change in the axial skeleton on a plain abdominal radiograph. Bone metastases being suspected from these findings, bone scintigraphy was performed. The bone scan demonstrated uniformly increased skeletal activity with faint soft-tissue activity. The findings of the bone scan, however, appeared atypical of the super scan caused by diffuse bone metastases, without any decrease in radioactivities of the appendicular skeleton and kidneys. Bone marrow scintigraphy with In-111 chloride demonstrated central marrow failure and peripheral expansion, which indicated the possibility of myelophthisis. The patient underwent bone marrow biopsy, which revealed replacement of the bone marrow by metastatic adenocarcinoma. Further examinations detected the primary lesion in the prostate. In this case, the findings of the bone scan were insufficient for the super scan, and might be categorized as a sub-super scan. It would be important to recognize this incomplete form of super scan as a rare scintigraphic pattern of diffuse bone marrow metastases.

The headless bone scan: an uncommon manifestation of metastatic superscan in carcinoma of the prostate

Five cases of metastatic prostatic carcinoma are presented. In each case, skeletal metastases were extensive, but the calvaria was not involved, resulting in a headless appearance. The mechanism for this scintigraphic manifestation is presented, and its value is emphasized.