Radioimmunoscintigraphy of recurrent, metastatic, or occult colorectal cancer with technetium Tc 99m 88BV59H21-2V67-66 (HumaSPECT-Tc), a totally human monoclonal antibody. Patient management benefit from a phase III multicenter study

Optimizing the radiosynthesis of [68Ga]DOTA-MLN6907 peptide containing three disulfide cyclization bonds - a GCC specific chelate for clinical radiopharmaceuticals

In the present study, the effect of radiolabeling conditions on radiolabeling efficiency and achievable specific activity of a DOTA-conjugated highly-lipophilic peptide containing three disulfide cyclization bonds was examined. The peptide is designed to bind specifically (with high affinity) to cell-surface receptor guanylyl cyclase C (GCC), which is universally expressed by colorectal cancer cells. The effect of systematic variation of chemical parameters pH, mass of peptide, acetate buffer concentration (ionic strength), and inclusion of ethanol in the radiolabeling reaction vessel on achievable specific activity and labeling efficiency was examined. In addition, a unique approach to acetone-based elution of ⁶⁸Ga from an initial cation-exchange pre-concentration column is introduced, which improved radiochemical yield and radiochemical purity. For the evaluation of the acetone-based method, two different post-radiolabeling reverse-phase (C18) approaches to purify the final radiolabeled peptide were tested. These results revealed the potential for peptide degradation via the cleavage of disulfide cyclization bonds to form free thiols when using one of these C18 cartridges. The final optimized procedure enabled radiolabeling efficiency of greater than 99% and specific activity greater than 35 MBq/nmole in less than 30 min. The optimized parameters were amenable to the use of an automated ⁶⁸Ge/⁶⁸Ga generator and fluid-handling system for clinical production of the GCC receptor-specific [⁶⁸Ga]DOTA-MLN6907 peptide. The chemical characteristics of individual peptides govern the most appropriate radiolabeling conditions for the preparation of radiopharmaceuticals.

In Vitro and in Vivo Comparison of Human Escherichia coli Heat-Stable Peptide Analogues Incorporating the 111In-DOTA Group and Distinct Linker Moieties

Three human Escherichia coli heat-stable peptide (STh) analogues, each containing a DOTA chelating group, were synthesized by SPPS and oxidative refolding and compared in in vitro and in vivo systems. One analogue, DOTA-F19-STh(1-19), contains an N-terminal DOTA group attached via an amide bond linkage to an STh moiety which is essentially wild-type except for a Tyr to Phe alteration at position 19 of the molecule. A second analogue, DOTA-R1,4,F19-STh(1-19), differs from the first in that asparagine residues in positions 1 and 4 have been altered to arginine residues in order to examine the effect of positively charged groups in the linker domain. A third analogue, DOTA-11AUN-F19-STh(1-19), differs from the first in that it incorporates an 11-aminoundecanoic acid spacer group between the DOTA group and the first asparagine residue. In vitro competitive binding assays utilizing T-84 human colon cancer cells demonstrated that significant alterations to the N-terminal region of the STh molecule were well tolerated and did not significantly affect binding affinity of STh for the guanylyl cyclase C (GC-C) receptor. Internalization and efflux studies of the indium-labeled species demonstrated that inclusion of positive charge in the linker moiety inhibits internalization of the compound within tumor cells. The characteristics of the three analogues were compared in an in vivo model utilizing T-84 human colon cancer cell xenografts in SCID mice. Clearance of all analogues was rapid, primarily via renal excretion into the urine, with >89% ID excreted into the urine at 1 h pi for all analogues. The 111In-DOTA-R1,4,F19-STh(1-19) and 111In-DOTA-11AUN-F19-STh(1-19) analogues both had longer residence times in the blood than did the 111In-DOTA-F19-STh(1-19) analogue, probably accounting for increased %ID/g values for tumors and nontarget tissues at 1 h pi. At 4 h pi, significant differences between analogues were only seen with respect to metabolic routes of excretion, indicating that increased blood residence time did not result in increased tumor residualization. Reduction of hepatic uptake of these compounds, however, could have significance in the development of agents for the imaging of hepatic metastases. The ability to manipulate in vivo pharmacodynamics and tumor uptake of radiolabeled STh peptides through modification of linker moieties is under continuing investigation in order to produce optimal imaging and therapeutic radiopharmaceuticals.

Usefulness of FDG-PET scan in the assessment of suspected metastatic or recurrent adenocarcinoma of the colon and rectum

PURPOSE

The purpose of this study was to evaluate the clinical efficacy of positron emission tomography with 2-[18F] fluoro-2-deoxy-D-glucose compared with computed tomography plus other conventional diagnostic studies in patients suspected of having metastatic or recurrent colorectal adenocarcinoma.

METHODS

The records of 105 patients who underwent 101 computed tomography and 109 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography scans for suspected metastatic or recurrent colorectal adenocarcinoma were reviewed. Clinical correlation was confirmed at time of operation, histopathologically, or by clinical course.

RESULTS

The overall sensitivity and specificity of 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography in detection of clinically relevant tumor were higher (87 and 68 percent) than for computed tomography plus other conventional diagnostic studies (66 and 59 percent). The sensitivity of 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography in detecting mucinous cancer was lower (58 percent; n = 16) than for nonmucinous cancer (92 percent; n = 93). The sensitivity of 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography in detecting locoregional recurrence (n = 70) was higher than for computed tomography plus colonoscopy (90 vs. 71 percent, respectively). The sensitivity of 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography in detecting hepatic metastasis (n = 101) was higher than for computed tomography (89 vs. 71 percent). The sensitivity of 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography in detecting extrahepatic metastases exclusive of locoregional recurrence (n = 101) was higher than for computed tomography plus other conventional diagnostic studies (94 vs. 67 percent). 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography altered clinical management in a beneficial manner in 26 percent of cases (26/101) when compared with evaluation by computed tomography plus other conventional diagnostic studies.

CONCLUSION

2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography is more sensitive than computed tomography for the detection of metastatic or recurrent colorectal cancer and may improve clinical management in one-quarter of cases. However, 2-[18F] fluoro-2-deoxy-D-glucose positron emission tomography is not as sensitive in detecting mucinous adenocarcinoma, possibly because of the relative hypocellularity of these tumors.

Hepatobiliary surgery

The transformation of liver and biliary tract surgery into a full speciality began with the application of functional anatomy to segmental surgery in the 1950's, reinforced by ultrasound and new imaging techniques. The spectrum of gall-stone disease encountered by the hepatobiliary surgeon has changed with the laparoscopic approach to cholecystectomy. There is increased need for conservation techniques to repair the bile duct injuries that arise more often in the laparoscopic approach to cholecystectomy. These and other surgical interventions on the bile ducts should be selected as a function of risk versus benefit in relation to the patient's requirements and the institutional expertise. Bile duct cancers, including hilar cholangiocarcinoma, and gallbladder cancers have a dismal reputation, but evidence is accumulating for better survivals from aggressive approaches performed by specialist hepatobiliary surgeons. Hepatic surgery has increased in safety and effectiveness, largely due to the segmental approach, but also to experience with techniques for vascular control and exclusion used in liver transplantation. Techniques such as portal vein embolisation, which induces hypertrophy of the future remnant liver, percutaneous local tumour destruction using cryotherapy or radiofrequency tumour coagulation and more effective chemotherapy are beginning to increase the number of patients who can undergo curative resection. In liver transplantation, segmental surgery has been applied to graft reduction and to split liver grafts, and is opening new perspectives for living donor transplantation. Today the limitation to survival in primary and metastatic liver cancer lies not in the surgical technique but in the difficulty of dealing with microscopic and extrahepatic disease. Progress in these fields will enable the hepatobiliary surgeon to further extend the possibilities for proposing curative resections.

Multidisciplinary management of metastatic colorectal cancer

When colorectal cancer metastasizes to distant organs, usually multiple sites are involved and treatment consists primarily of systemic chemotherapy and supportive care. Chemotherapeutic agents effective against metastatic colorectal cancer include 5-fluorouracil, often used in combination with leucovorin or methotrexate, and irinotecan (CPT-11). Median survival with optimal chemotherapy regimens ranges from 10 to 15 months. Less frequently, colorectal cancer metastasizes only to the liver or lung. In a minority of these cases, surgical resection can be performed and results in a median survival of 28-46 months for hepatic resections and 24-25 months for pulmonary resections. Five-year survival rates range from 24 to 38% and 21 to 44% for hepatic and pulmonary resections, respectively. For isolated liver metastases that are not surgically resectable, other regional therapies that can be considered are hepatic cryosurgery, radiofrequency ablation, and hepatic arterial infusion chemotherapy. Median survival following cryosurgery is between 26 and 30 months, while median survival following radiofrequency ablation has not been established in large series. Hepatic arterial infusion chemotherapy, especially with newer combination drug regimens, may increase survival in patients with isolated liver metastases compared to systemic chemotherapy, but this must be confirmed in randomized, prospective trials. Colorectal cancer metastases to the brain can be treated with radiation therapy or surgical resection, but median survival with treatment is less than one year.

Colorectal cancer screening and follow-up

Cancer of the colon and rectum is a significant health problem in the United States. Nearly 50% of the 186,000 patients diagnosed annually with colorectal cancer will eventually die of their disease. Because development of a colorectal carcinoma is most frequently preceded by the development of a well-recognized pre-malignant lesion, screening modalities can significantly impact the incidence and mortality rate of this disease. Population screening employing digital rectal examination, fecal occult blood testing and endoscopic examination of the rectum and colon has been demonstrated to reduce the risk of death from colorectal cancer. Screening regimens should be instituted at an earlier age and with increased frequency for patients in the highest risk categories. Patients who have been treated for a cancer of the colon or rectum should undergo surveillance at regular intervals in an attempt to identify recurrences of disease both in the residual colon and rectum and at distant sites. Most physicians and patients believe that intensive follow-up strategies will afford improved survival and quality of life, however few randomized studies examining the utility of intensive follow-up programs have been performed and the quality of cancer-related follow-up literature is generally poor. Good-quality clinical trials are needed to sort out which tests make a difference in the patient's long-term outcome. The algorithm for surveillance for recurrence in the future may be altered as newer testing modalities are developed.