Experimental radioimmunoguided surgery for peritoneal metastases of gastric cancer using anticarcinoembryonic antigen-specific T84.66 F(ab')2

Advances in molecular imaging for diagnosis of digestive tract cancers

Digestive tract cancers are common cancer types and have high incidence and mortality. Currently available diagnostic methods have some limitations that make an early and accurate diagnosis and prompt treatment difficult. Molecular imaging, which has been formally defined as visualization, characterization and measurement at the molecular level instead of the anatomic level, significantly increases the sensitivity and specificity of cancer detection. Several modalities have been utilized for molecular imaging in digestive tract cancers, such as endoscopy, scintigraphy (PET/SPECT), magnetic resonance imaging (MRI), and ultrasound (US). Antibodies, peptides, and aptamers are classes of molecular probes that have been extensively used as affinity ligands. After being conjugated with various labels such as radioisotopes, fluorophore, supermagnetic or paramagnetic metals and microbubbles, the probes can specifically target tumor cells and stroma and are used with imaging modalities to detect cancers. Molecular imaging is a methodology for not only the early detection of cancer, but also the judgment of tumor staging and the guidance of therapy. With the development of new instrument and probes, as well as multi-modal platforms, molecular imaging has been gradually perfected and taken from bench to bedside, bringing opportunities for early, accurate and comprehensive diagnosis of digestive tract cancers.

Radiation dose to surgical staff from positron-emitter-based localization and radiosurgery of tumors

Surgical tissue characterization based on radiotracer uptake has become much more common in recent years, particularly due to the advent of the sentinel lymph node biopsy technique. Radiolabeled pharmaceuticals are used with hand-held gamma-sensitive probes, which are capable of localizing small tumors and lymph nodes that are first identified via scintigraphy. The radiation safety of such radioguided procedures, which typically employ 99mTc, has been well established. Now, with the emergence of 18F-fluorodeoxyglucose (18FDG) as a widely used tracer for PET imaging of cancer patients, there is increasing interest in the possibility of utilizing 18FDG for intraoperative tumor detection. First, though, the exposure to operating room personnel must be shown to be at a safe level. Due to the short half-life of 18F, the exposure rate will vary significantly with the start time post-injection as well as the duration of the procedure. The aim of this investigation is to determine empirically an exposure rate equation that can be integrated to estimate the exposure to a surgeon and assistants, from patients injected with 18FDG, over an arbitrarily chosen time interval. The study was conducted by measuring the radiation exposure rate from hospital in-patients receiving 18FDG-PET scans at various times from one to seven hours post injection; the empirical equation was determined from the plot of exposure rate vs. time for all patients. The resulting effective dose equivalent for the surgeon for typical values of injected activity, delay time and procedure duration was approximately 60 microSv.

Recent advances in the treatment of peritoneal dissemination of gastrointestinal cancers by nucleoside antimetabolites

Peritoneal dissemination is the most common cause of metastasis from malignancies in the abdominal cavity. There are no standard treatments for peritoneal dissemination and the results are poor. The reasons for this are as follows: (1) no effective chemotherapeutic agents have been identified or developed; (2) surgical cytoreduction has little effect on survival improvement; and (3) the molecular mechanisms of peritoneal dissemination have not been clarified and no therapy against the target molecules has been developed. However, studies on the molecular mechanisms of peritoneal dissemination have elucidated some of the target molecules and the development of new multimodal therapies has also improved survival. Early postoperative intraperitoneal chemotherapy, hyperthermic intraperitoneal perfusion chemotherapy and neoadjuvant intraperitoneal-systemic chemotherapy have been newly developed, and a novel surgical therapy named peritonectomy has been proposed to perform complete cytoreduction of peritoneal dissemination. At present, these approaches appear to be effective therapeutic modalities for peritoneal dissemination. However, TS-1 and capecitabine have shown worthwhile results in recent clinical trials for patients with advanced gastric cancer. We recently found that newly developed antitumor cytosine nucleoside analogs show a survival advantage in peritoneal dissemination models using human cancer cells. These non-fluoropyrimidine nucleosides may potentially help to improve the poor prognosis observed in patients with advanced cancers involving peritoneal dissemination.