Joint EANM/SNMMI/ANZSNM practice guidelines/procedure standards on recommended use of [18F]FDG PET/CT imaging during immunomodulatory treatments in patients with solid tumors version 1.0.

PURPOSE: The goal of this guideline/procedure standard is to assist nuclear medicine physicians, other nuclear medicine professionals, oncologists or other medical specialists for recommended use of [18F]FDG PET/CT in oncological patients undergoing immunotherapy, with special focus on response assessment in solid tumors. METHODS: In a cooperative effort between the EANM, the SNMMI and the ANZSNM, clinical indications, recommended imaging procedures and reporting standards have been agreed upon and summarized in this joint guideline/procedure standard. CONCLUSIONS: The field of immuno-oncology is rapidly evolving, and this guideline/procedure standard should not be seen as definitive, but rather as a guidance document standardizing the use and interpretation of [18F]FDG PET/CT during immunotherapy. Local variations to this guideline should be taken into consideration. PREAMBLE: The European Association of Nuclear Medicine (EANM) is a professional non-profit medical association founded in 1985 to facilitate worldwide communication among individuals pursuing clinical and academic excellence in nuclear medicine. The Society of Nuclear Medicine and Molecular Imaging (SNMMI) is an international scientific and professional organization founded in 1954 to promote science, technology and practical application of nuclear medicine. The Australian and New Zealand Society of Nuclear Medicine (ANZSNM), founded in 1969, represents the major professional society fostering the technical and professional development of nuclear medicine practice across Australia and New Zealand. It promotes excellence in the nuclear medicine profession through education, research and a commitment to the highest professional standards. EANM, SNMMI and ANZSNM members are physicians, technologists, physicists and scientists specialized in the research and clinical practice of nuclear medicine. All three societies will periodically put forth new standards/guidelines for nuclear medicine practice to help advance the science of nuclear medicine and improve service to patients. Existing standards/guidelines will be reviewed for revision or renewal, as appropriate, on their fifth anniversary or sooner, if indicated. Each standard/guideline, representing a policy statement by the EANM/SNMMI/ANZSNM, has undergone a thorough consensus process, entailing extensive review. These societies recognize that the safe and effective use of diagnostic nuclear medicine imaging requires particular training and skills, as described in each document. These standards/guidelines are educational tools designed to assist practitioners in providing appropriate and effective nuclear medicine care for patients. These guidelines are consensus documents based on current knowledge. They are not intended to be inflexible rules or requirements of practice, nor should they be used to establish a legal standard of care. For these reasons and those set forth below, the EANM, SNMMI and ANZSNM caution against the use of these standards/guidelines in litigation in which the clinical decisions of a practitioner are called into question. The ultimate judgment regarding the propriety of any specific procedure or course of action must be made by medical professionals considering the unique circumstances of each case. Thus, there is no implication that an action differing from what is laid out in the guidelines/procedure standards, standing alone, is below standard of care. To the contrary, a conscientious practitioner may responsibly adopt a course of action different from that set forth in the standards/guidelines when, in the reasonable judgment of the practitioner, such course of action is indicated by the condition of the patient, limitations of available resources or advances in knowledge or technology subsequent to publication of the guidelines/procedure standards. The practice of medicine involves not only the science, but also the art of dealing with the prevention, diagnosis, alleviation and treatment of disease. The variety and complexity of human conditions make it impossible for general guidelines to consistently allow for an accurate diagnosis to be reached or a particular treatment response to be predicted. Therefore, it should be recognized that adherence to these standards/ guidelines will not ensure a successful outcome. All that should be expected is that practitioners follow a reasonable course of action, based on their level of training, current knowledge, clinical practice guidelines, available resources and the needs/context of the patient being treated. The sole purpose of these guidelines is to assist practitioners in achieving this objective. The present guideline/procedure standard was developed collaboratively by the EANM, the SNMMI and the ANZSNM, with the support of international experts in the field. They summarize also the views of the Oncology and Theranostics and the Inflammation and Infection Committees of the EANM, as well as the procedure standards committee of the SNMMI, and reflect recommendations for which the EANM and SNMMI cannot be held responsible. The recommendations should be taken into the context of good practice of nuclear medicine and do not substitute for national and international legal or regulatory provisions.

Effectiveness, safety and utilization of vismodegib in locally advanced basal cell carcinoma under real-world conditions in Germany - The non-interventional study NIELS.

BACKGROUND: Basal cell carcinoma (BCC) can arise by the uncontrolled proliferation of cells from multiple epidermal compartments due to aberrant activation of the Hedgehog (Hh) signalling pathway. Vismodegib, a small-molecule inhibitor of this pathway, is approved for treatment of patients with locally advanced (la) BCC inappropriate for surgery or radiotherapy or patients with symptomatic metastatic (m) BCC. OBJECTIVES: The aim of this non-interventional study was to assess effectiveness with a special focus on duration of response (DOR), safety and utilization of vismodegib for treatment of laBCC in daily practice in Germany. METHODS: This non-interventional study (NIS) observed treatment of laBCC with vismodegib according to the German label in clinical practice. All available patients who had received at least one dose of vismodegib between commercial availability of vismodegib in Germany (02 August 2013) and 3 years before end of study (31 March 2016) could be included and were documented retrospectively and/or prospectively for up to 3 years. Primary effectiveness variable was DOR. Assessment of tumour response was carried out by the treating physicians. Exploratory variables included utilization of vismodegib, decision makers for therapy and method of tumour response evaluation. All statistical analyses were descriptive. RESULTS: Between September 2015 and March 2019, 66 patients were observed at 26 German centres. The objective response rate (ORR) was 74.2% and the disease control rate (DCR) was 90.9%. The median DOR was 15.9 months (95% CI: 9.2; 25.7; n = 49 patients with response). The median progression-free survival (PFS) was 19.1 months and the median time to response (TTR) 2.7 months. A total of 340 adverse events were reported in 63 (95.5%) patients; no new safety signals were identified. CONCLUSIONS: The NIS NIELS shows effectiveness and safety of vismodegib in patients with laBCC. It confirms the transferability of the results of the pivotal trial into routine clinical practice.

Immunotherapy with imiquimod and interferon alfa for metastasized Merkel cell carcinoma.

Merkel cell carcinoma (mcc) is a highly aggressive neuroendocrine tumour of the skin. Remission rates are high with chemotherapy in patients with metastasis, but without any improvement in overall survival. We present the case of a 90-year-old woman with facial mcc. After radiation and surgery, the mcc recurred with widespread cutaneous and regional lymph node metastases. The metastases were treated with weekly intralesional injections of 1-2×10(6) IU interferon alfa-2a, accompanied by topical imiquimod 5% cream 3 times weekly. After partial regression, subcutaneous pegylated interferon alfa-2b was added at a dose of 30 µg weekly, which was then increased to 50 µg weekly. At 4 months after the start of immunotherapy, all cutaneous metastases and the intralesionally treated lymph node metastases receded. Interruption or reduction of systemic interferon application resulted in locoregional relapses that were successfully treated with surgery or intralesional interferon injections. The patient remains alive 30 months after initiation of immunotherapy, suggesting that locally metastasized mcc might be able to be controlled with local and systemic immunotherapy.

[Atypical fibroxanthoma of the scalp: overview and recent developments]. / Atypisches Fibroxanthom am Capillitium: Überblick und aktuelle Erkenntnisse.

Atypical fibroxanthoma (AFX) is a rare, low-malignant, mesenchymal tumor of the dermis and is assigned to the group of fibrohistiocytic tumors. The tumor occurs especially in photodamaged skin on the scalp of elderly men. A clinical diagnosis is not possible due to a multitude of possible differential diagnoses (leiomyosarcoma, squamous cell carcinoma, spindle cell malignant melanoma, dermatofibrosarcoma protuberans). Immunohistochemical and histological examinations should be performed to confirm the diagnosis. The tumor shows a very good prognosis after complete excision. Micrographically controlled surgery is considered as the treatment of choice.

[Post-vaccination granulomas caused by delayed-type reaction to aluminum salts]. / Impfgranulom bei Spättypallergie gegen Aluminiumsalze.

BACKGROUND: Aluminium salts are common adjuvants in all established inactivated vaccines. They are necessary to activate the humoral immune system. In the 1990s a Swedish study on an acellular vaccination against pertussis was started. Until 2013, 745 of 760,000 children with pruritic subcutaneous nodules were identified. In 77 % of these children a contact allergy to aluminium could be proven. Contact allergy to aluminium induced by vaccines causes pruritic subcutaneous nodules at the vaccination site. During infections of the upper respiratory tract the pruritus often escalates with inflammatory, erythematous and urticarial plaques. CONCLUSIONS: The use of solutions containing aluminium salts for specific immunotherapy is contraindicated in the case of contact allergy to aluminium. Intramuscular injections of inactivated vaccines can be employed to avoid granuloma formation.

[Erlotinib-induced acneiform eruption]. / Erlotinib-assoziiertes akneiformes exanthem.

A 73-year-old man has been suffering from a pulmonary adenocarcinoma for three years. He has been treated with the EGF-inhibitor erlotinib for the past 18 months. While taking this medication he developed a progressive papulopustular rash on his face and trunk which later spread to his thighs. Topical treatment with methylprednisolone and nadifloxacin, as well as short courses of systemic doxycycline and ciprofloxacin, led to marked improvement and control of his skin condition.

Do antidiabetic medications play a specific role in differentiated thyroid cancer compared to other cancer types?

The risk for differentiated thyroid cancer, like for many other types of cancer, is increased in obese individuals and people with intermediate hyperglycaemia. The incidence of all cancers, with the exception of thyroid cancer, is also increased in type 2 diabetes mellitus patients. The review compares the prevalence of thyroid carcinoma and other cancers in obese, people with intermediate hyperglycaemia and patients with diabetes and summarizes mode of action and anti-tumourigenic effect of common antidiabetic medications. The over-expression of dipeptidyl peptidase IV in the tumours, not seen in the other cancer types, is suggested as a potential reason for the unique situation in thyroid cancer.

Perspectives on joint EANM/SNMMI/ANZSNM practice guidelines/procedure standards for [18F]FDG PET/CT imaging during immunomodulatory treatments in patients with solid tumors.

Response assessment in the context of immunomodulatory treatments represents a major challenge for the medical imaging community and requires a multidisciplinary approach with involvement of oncologists, radiologists, and nuclear medicine specialists. There is evolving evidence that [18F]FDG PET/CT is a useful diagnostic modality for this purpose. The clinical indications for, and the principal aspects of its standardization in this context have been detailed in the recently published "Joint EANM/SNMMI/ANZSNM practice guidelines/procedure standards on recommended use of [18F]FDG PET/CT imaging during immunomodulatory treatments in patients with solid tumors version 1.0". These recommendations arose from a fruitful collaboration between international nuclear medicine societies and experts in cancer treatment. In this perspective, the key elements of the initiative are reported, summarizing the core aspects of the guidelines for radiologists and nuclear medicine physicians. Beyond the previous guidelines, this perspective adds further commentary on how this technology can advance development of novel therapeutic approaches and guide management of individual patients.

Decrease in dipeptidyl peptidase IV activity is linked to the efficacy of differentiating compounds in follicular thyroid carcinoma cell lines.

Metastasized differentiated thyroid carcinoma is treated by surgery followed by radioiodine remnant ablation. The application of differentiating agents is a possibility of increasing the efficacy of radioiodine therapy. We evaluated DPP IV and aminopeptidase N, both linked to malignancy in thyroid carcinoma, and dipeptidyl peptidase II activities in human follicular thyroid carcinoma cell lines upon treatment with retinol, apicidine, and lovastatin as differentiating agents. Decrease of dipeptidyl peptidase IV (DPP IV) activity may play a role in the differentiating action. In the human cancer cell lines FTC 138 and 238, high DPP IV and low aminopeptidase N activities were recorded. Retinol treatment induced increases in thyroid-specific protein expression [thyroglobulin and sodium-iodide symporter (NIS)], increase in iodide uptake, and decrease in thymidine uptake accompanied by decrease in DPP IV activity. Decreases in DPP IV activities were also seen upon apicidine and lovastatin treatment, which also increased differentiation of the transformed thyrocytes. Our results demonstrate a link between decrease in DPP IV activity and increase in iodide uptake upon stimulation with differentiating agents.

[Perioperative anaphylaxis caused by rocuronium allergy in a child]. / Perioperative Anaphylaxie aufgrund einer Rocuroniumallergie bei einem Kind.

During the induction of anesthesia for strabismus correction, a six-year-old boy suffered anaphylaxis with hypotension. Midazolam, propofol, sufentanil, rocuronium, dexamethasone and ibuprofen had been administered. The boy's history failed to reveal any drug allergies. Intracutaneous testings with drugs used for anesthesia and other muscle relaxants verified a positive reaction to rocuronium as well as to cisatracurium, mivacurium, vecuronium and atracurium. There was no reaction to suxamethonium.

[Side effects of novel cancer immunotherapies]. / Nebenwirkungen neuer onkologischer Immuntherapien.

Systemic treatment with immune checkpoint inhibitors (ICI) has revolutionized the treatment of hematological and oncological diseases in recent years. The mechanism of action hinges on enhancing the natural ability of the immune system to eliminate malignant cells. The most important substances in this arena include inhibitors of PD­1, PD-L1 and CTLA­4. As a consequence, the spectrum of treatment-associated adverse reactions is shifting away from classical cytotoxic effects (e.g. pancytopenia and polyneuropathy) towards novel entities of immune-mediated complex diseases. These so-called immune-related adverse events (irAEs) can involve any organ system and mimic known classical autoimmune conditions. Timely recognition of irAEs is the key for rapid initiation of a suitable treatment and is especially challenging in the clinical routine as it requires an intensive interdisciplinary management. Nephrologists are particularly confronted with this kind of problem due to the highly interdisciplinary nature of their work. This article summarizes the broad spectrum of currently known renal and more frequently occuring non-renal forms of irAEs and aims to prime the reader on diagnostic and therapeutic options.

[HPV type 33-associated penile intraepithelial neoplasia (PIN)]. / HPV-Typ-33-assoziierte intraepitheliale Neoplasie des Penis (PIN).

For appoximately 6 month a 69-year old man had been suffering from an itching scaly skin change of the penis. Virological and histological examinations confirmed the diagnosis of an intraepithelial neoplasia induced by an infection with human papillomavirus (HPV) type 33. HPV type 33 is comparatively rarely detected in intraepithelial neoplasia. In anogenital lesions intraepithelial neoplasia should be considered and confirmed via histological and virological examinations.

[HPV type 16-associated anal intraepithelial neoplasia (AIN)]. / HPV-Typ-16-assoziierte anale intraepitheliale Neoplasie (AIN).

A 25-year-old woman had suffered from a perianal ulcer for approximately 1 year. Topical and systemic treatments had been unsuccessful. Employing virologic and histologic techniques, we confirmed the diagnosis of an intraepithelial neoplasia. Anal intraepithelial neoplasia (AIN) is induced by carcinogenic human papillomaviruses. It can occur anywhere in the anogenital area. Because of its frequency, AIN is a crucial differential diagnosis for lesions of the anogenital area region failing to respond to standard therapies.

[Congenital unilateral linear porokeratosis]. / Kongenitale lineare unilaterale Porokeratose.

Porokeratosis is a disorder of epidermal keratinization. A 27-year-old woman had papular, linearly arranged, hyperkeratotic lesions on the right foot since birth. Over the course of her life, the lesions progressed to involve the entire right leg and extended to the right side of her trunk, the right arm and chin. The clinical diagnosis of unilateral linear porokeratosis was confirmed by histopathology.

[Lymph node dissection in papillary and follicular thyroid cancer]. / Lymphknotendissektion beim papillären und follikulären Schilddrüsenkarzinom.

BACKGROUND: There is still unresolved debate about the optimal surgical management of papillary (PTC) and follicular (FTC) thyroid cancer regarding lymph node dissection. So far the German guidelines recommend the same extent of surgery for both tumors. PATIENTS AND METHODS: This study is based on 626 patients with PTC and 191 with FTC from a group of 1062 own patients with thyroid malignancies. The extent of surgery, tumor size, and pN status were analysed. The results were compared with those in the current literature. RESULTS: Tumors < or = 20 mm in size were found significantly more often in PTC than FTC (69.6% vs 28.3%, P<0.05). Positive lymph nodes were found significantly more often in PTC than FTC as well (33.2% vs 5.2%, P<0.05). In PTC up to 10 mm and from 11 mm to 20 mm in size, 16% and 34.4% of patients, respectively, showed positive lymph nodes. In FTC positive lymph nodes occurred only in tumors >25 mm. CONCLUSION: Due to prevalence and importance of lymph node metastasis differing between PTC and FTC, we recommend treating both tumor entities differently. For PTC a more extended lymph dissection is necessary, even in tumors < or = 20 mm. In small FTC it seems adequate to limit the operation to thyroidectomy without prophylactic lymph dissection.

Epidemiology of invasive Streptococcus pyogenes infections in Germany, 1996-2002: results from a voluntary laboratory surveillance system.

A nationwide voluntary laboratory-based surveillance study of invasive Streptococcus pyogenes (group A streptococcus; GAS) infections was conducted in Germany between 1996 and 2002. Demographical and clinical information concerning the patients was obtained from the medical files. Multiple logistic regression analysis was used to determine risk-factors for fatal outcome. Invasive isolates were obtained from 475 patients, with 251 (52.8%) of the isolates cultured from blood. The most frequent emm types were emm1 (36.4%), emm28 (8.8%) and emm3 (8%). The speA, speC and ssa genes were present at variable frequencies in different emm types. The highest frequencies of speA and speC were found in emm1 (speA, 93.6%) and emm4 (speC, 94.7%), respectively. The estimated annual incidence of invasive GAS disease for 1997-2002 was 0.1 cases/100 000 individuals. This apparently low incidence rate might be explained by the voluntary nature of the surveillance system, resulting in relatively few cases being referred to the laboratory. Complete clinical information was available for 165 cases. The overall case fatality rate was 40.6%, and was highest (65.2%) in the group aged 60-69 years. Shock, an age of >or=30 years and adult respiratory distress syndrome were predictors of a fatal outcome in a multiple logistic regression analysis. Overall, 6.7% of the cases were considered to be nosocomial, and nine cases of puerperal sepsis were observed. The study underscores the importance of invasive S. pyogenes disease in Germany.

Radioiodine ablation of thyroid remnants after preparation with recombinant human thyrotropin in differentiated thyroid carcinoma: results of an international, randomized, controlled study.

CONTEXT: After surgery for differentiated thyroid carcinoma, many patients are treated with radioiodine to ablate remnant thyroid tissue. This procedure has been performed with the patient in the hypothyroid state to promote endogenous TSH stimulation and is often associated with hypothyroid symptoms and impaired quality of life. OBJECTIVE AND INTERVENTION: This international, randomized, controlled, multicenter trial aimed to compare the efficacy and safety of recombinant human TSH (rhTSH) to prepare euthyroid patients on L-thyroxine therapy (euthyroid group) to ablate remnant thyroid tissue with 3.7 GBq (100 mCi) 131I, compared with that with conventional remnant ablation performed in the hypothyroid state (hypothyroid group). Quality of life was determined at the time of randomization and ablation. After the administration of the 131-I dose, the rate of radiation clearance from blood, thyroid remnant, and whole body was measured. RESULTS: The predefined primary criterion for successful ablation was "no visible uptake in the thyroid bed, or if visible, fractional uptake less than 0.1%" on neck scans performed 8 months after therapy and was satisfied in 100% of patients in both groups. A secondary criterion for ablation, an rhTSH-stimulated serum thyroglobulin concentration less than 2 ng/ml, was fulfilled by 23 of 24 (96%) euthyroid patients and 18 of 21 (86%) hypothyroid patients (P = 0.2341). Quality of life was well preserved in the euthyroid group, compared with the hypothyroid group, as demonstrated by their lower pretreatment scores on the Billewicz scale for hypothyroid signs and symptoms, 27 +/- 7 vs. 18 +/- 4 (P < 0.0001) and their significantly higher Short Form-36 Health Assessment Scale scores in five of eight categories. Euthyroid patients had a statistically significant one third lower radiation dose to the blood, compared with patients in the hypothyroid group. CONCLUSIONS: This study demonstrates comparable remnant ablation rates in patients prepared for 131I remnant ablation with 3.7 GBq by either administering rhTSH or withholding thyroid hormone. rhTSH-prepared patients maintained a higher quality of life and received less radiation exposure to the blood.

Products of cells cultured from gliomas. V. Cytology and morphometry of two cell types cultured from glioma.

Explants of cells of a human glioma were evaluated with the nuclear fluorochrome 4',6-diamidino-2-phenylindole, by phase-contrast illumination, and by Giemsa staining correlated with double immunofluorescence for glial fibrillary acidic protein (GFAP) and fibronectin (FN). FN-positive (FN+) cells lacked GFAP detectable by immunofluorescence. Their mean nuclear-to-cytoplasmic ratio was large (0.192). Actual mean areas of nuclei (1,252 microns2) and cytoplasm (8,376 microns2) of FN+ cells compared with mean areas of fibroblasts suggested that the high nuclear-to-cytoplasmic ratio of FN+ cells was due to their microscopically evident reduced cytoplasmic spreading rather than to larger nuclei. Some FN+ cells showed marked variation in nuclear and nucleolar size and shape. Others had abnormal mitoses or hyperchromatic nuclei. GFAP-positive (GFAP+) cells lacked FN detectable by immunofluorescence. GFAP+ cells were smaller and less round than FN+ cells. Their usual location was growing on a layer of FN+ cells. The mean nuclear-to-cytoplasmic ratio (0.245) of GFAP+ cells was the highest in the study, surpassing the ratio of the continuous glioma line LM (0.176). Mean areas of nuclei (289 microns2) and of cytoplasm (1,350 microns2) of GFAP+ cells suggested that their high nuclear-to-cytoplasmic ratio was due to their microscopically evident reduced cytoplasmic spreading. Reduced spreading was associated with extension of long, thin cytoplasmic processes. The majority of GFAP+ cells showed marked cytoplasmic basophilia, nuclear hyperchromasia, and clumped chromatin. Features observed in both FN+ and GFAP+ cells from this high-grade astrocytoma are features associated with malignant transformation in more thoroughly studied tumor systems.

[The role of intraoperative ultrasound in surgery for benign nodular goiter]. / Die Wertigkeit des intraoperativen Ultraschalls bei der benignen Knotenstruma.

BACKGROUND: In treating benign nodular goiter, selective surgery taking into account morphology and function is better than standard subtotal resection for reducing the frequency of nodules in the thyroid remnant. Intraoperative ultrasound (IOPUS) may additionally influence operative radicality and also the incidence of remaining nodules. METHODS: One hundred consecutive patients with benign nodular goiter were operated on with IOPUS; the specimens were compared with results of preoperative ultrasound and intraoperative palpation. Of these patients, 80 were reinvestigated after 3+/-1.6 years. A series of 80 patients with the same operative strategy but without IOPUS was used as control group, having been reinvestigated sonographically 1 year postoperatively, and was compared to the IOPUS group with respect to operative procedures, size of remnants, and sonography of lesions in thyroid remnants. RESULTS: In 35% of the thyroid lobes, preoperatively undetected nodules could be identified additionally by IOPUS, which also provided information on extent and structure in a further 20%. It resulted in the indication for more radical surgery in 24% and greater tissue preservation in 10%. Compared to surgery without IOPUS, IOPUS-guided surgery was more radical (total lobectomy in 40% vs 24%, nonresected lobes in 16% vs 26%, P<0.05) and showed a lower incidence of nodules in remnants at follow-up (2.5% vs 12.5%, P<0.05). CONCLUSIONS: With IOPUS, more nodules are detectable, size and structure of the remnants are optimized, and the number of nodular lesions in thyroid remnants is lower. Thus, an even lower risk of recurrence can be expected for long-term follow-up. All in all, the routine use of IOPUS can be advocated, with maintenance of the selective operative strategy.

Disulfide bond-targeted radiolabeling: tumor specificity of a streptavidin-biotinylated monoclonal antibody complex.

A site-specific labeling method was developed in which sulfhydryl groups of a murine IgG2a anti-ovarian monoclonal antibody, 5G6.4, were biotinylated with N-iodoacetyl-N'-biotinylhexylenediamine (Compound 1) following partial reduction of disulfide bonds with dithiothreitol. Reaction of 1-alkylated 5G6.4 with 125I-streptavidin gave immunoreactive streptavidin-1-biotinylated complexes. Radio-fast protein liquid chromatography data were consistent with the formation of a stable monovalent streptavidin-half-antibody complex as the major species. In vivo specific localization of these radioantibody conjugates to human tumor xenografts of ovarian carcinoma was confirmed by a comparative biodistribution study in nude mice using as a control the nonspecific 125I-streptavidin-1-alkylated UPC-10 (an irrelevant IgG2a monoclonal antibody) complex prepared analogously as described above. Tumor uptake for radiolabeled 5G6.4 [0.279 +/- 0.041% (SE) kg injection dose/g) was significantly greater [P less than 0.025] than for UPC-10 [0.165 +/- 0.027% kg injection dose/g]. The tumor:blood ratio (7.38 +/- 1.285) for 5G6.4 was approximately 3 times that for UPC-10 (2.48 +/- 0.708, P less than 0.01). This sulfhydryl site-directed approach demonstrated that reduced disulfides of monoclonal antibodies are viable sites for attaching labels without significant loss of in vitro and in vivo immunoreactivity.