Comparison of radioimmunodetection with other imaging methods in evaluating local relapses of colorectal carcinoma

Follow-up of patients with colorectal cancer: numbers needed to test and treat

Follow-up after curative treatment of patients with colorectal cancer has as its main aims the quality assessment of the treatment given, patient support, and improved outcome by the early detection and treatment of cancer recurrence. How often, and to what extent, the final aim, improved survival, is indeed realised is so far unclear. A literature search was performed to provide quantitative estimates for the main determinants of the effectiveness of the follow-up. Data were extracted from a total of 267 articles and databases, and were aggregated using modern meta-analytic methods. In order to provide one more colorectal cancer patient with long-term survival through follow-up, 360 positive follow-up tests and 11 operations for colorectal cancer recurrence are needed. In the remaining 359 tests and 10 operations, either no gains are achieved or harm is done. As the third aim of colorectal cancer follow-up, improved survival, is realised in only few patients, follow-up should focus less on diagnosis and treatment of recurrences. It should be of limited intensity and duration (3 years), and the search for preclinical cancer recurrence should primarily be performed by carcino-embryonic antigen (CEA) testing and ultrasound (US). The focus of colorectal cancer follow-up should shift from the early detection of recurrence towards quality assessment and patient support. As support that is as good or even better can be provided by a patient's general practitioner (GP) or by specialised nursing personnel, there is no need for routine follow-up to be performed by the surgeon.

Can postoperative surveillance with serial CEA immunoscintigraphy detect resectable rectal cancer recurrence and potentially improve tumor-free survival?

BACKGROUND

This study was performed to determine if postoperative serial monitoring of rectal cancer patients can be performed with an immunoscintigraphic imaging test for carcinoembryonic antigen (CEA). It was also of interest to assess whether this test, in combination with standard monitoring procedures used in an intensive surveillance plan, can result in the identification of surgically salvageable patients.

STUDY DESIGN

Forty consecutive resected Dukes' B and C rectal cancer patients underwent a prospective, single-institution, surveillance trial of physical examination (including digital rectal examination), endoscopy, CT of the abdomen and pelvis, liver ultrasound, chest x-ray, blood CEA, and CEA immunoscintigraphy with arcitumomab (CEA-Scan, Immunomedics, Morris Plains, NJ) every 6 months for the first 2 years and every 12 months for the next 3 years after initial operation. Outcomes were compared with those from a similar group of 69 patients treated previously at the same institution but without CEA imaging.

RESULTS

A total of 219 CEA imaging studies were performed without any significant adverse effects or immune responses, and resulted in lesion sensitivity, specificity, accuracy, and positive and negative predictive values of 94.1%, 97.5%, 97.3%, 76.2%, and 99.5%, respectively. Of the 40 patients, 16 developed 22 surgically confirmed local or distant recurrences, and CEA imaging correctly disclosed 82% of these lesions pre-operatively. All of the patients found to have recurrences had at least one tumor site by CEA imaging; only 6 of 16 had elevated blood CEA titers. On a patient-basis, there was a sensitivity of 100%, a specificity of 79.2%, an accuracy of 87.5%, and positive and negative predictive values of 76.2% and 100%, respectively. The potential therapeutic benefit of serial arcitumomab imaging is suggested by the fact that 6 of 16 patients (37.5%) with recurrence underwent potentially curative second-look operations, compared with 6 of 69 (8.7%) of a comparable population studied at this institution during an earlier 6-year period, using all of the same tests except CEA imaging. None of the patients in this historic control group survived more than 21 months, although the mean survival of the six patients resected for cure in the study population was 35 months (range 11 to 69 months). During 6 years of followup, three of the six re-resected patients eventually died of cancer recurrence, two died from other causes (and were confirmed by necropsy to be tumor-free), and one patient is still free of disease in the sixth year. CEA scanning appeared to be more predictive of recurrence than blood CEA testing or other diagnostic modalities.

CONCLUSIONS

Arcitumomab inclusion in intensive surveillance of patients with resected rectal cancer can disclose tumor recurrence at a stage that allowed surgical salvage therapy in 37.5% of the 16 patients with recurrence who had second-look surgery, and in 19% the patients were free of disease during longterm followup. This pilot study suggests that a randomized prospective trial comparing standard surveillance procedures to the use of CEA imaging added thereto should be undertaken.

A novel immunoscintigraphy technique using metabolizable linker with angiotensin II treatment

Immunoscintigraphy is a tumour imaging technique that can have specificity, but high background radioactivity makes it difficult to obtain tumour imaging soon after the injection of radioconjugate. The aim of this study is to see whether clear tumour images can be obtained soon after injection of a radiolabelled reagent using a new linker with antibody fragments (Fab), in conditions of induced hypertension in mice. Fab fragments of a murine monoclonal antibody against human osteosarcoma were labelled with radioiodinated 3′-iodohippuryl N-ɛ-maleoyl-L-lysine (HML) and were injected intravenously to tumour-bearing mice. Angiotensin II was administered for 4 h before and for 1 h after the injection of radiolabelled Fab. Kidney uptake of ¹²⁵I-labelled-HML-Fab was much lower than that of ¹²⁵I-labelled-Fab radioiodinated by the chloramine-T method, and the radioactivity of tumour was increased approximately two-fold by angiotensin II treatment at 3 h after injection, indicating high tumour-to-normal tissue ratios. A clear tumour image was obtained with ¹³¹I-labelled-HML-Fab at 3 h post-injection. The use of HML as a radiolabelling reagent, combined with angiotensin II treatment, efficiently improved tumour targeting and enabled the imaging of tumours. These results suggest the feasibility of PET scan using antibody fragment labelled with ¹⁸F-fluorine substitute for radioiodine. © 1999 Cancer Research Campaign

Rectal imaging and cancer

Rectal imaging has evolved substantially during the past 25 years and now offers surgeons exquisite anatomic detail and physiologic information. Dynamic cystoproctography, helical computed tomography, endoscopic ultrasonography, endorectal magnetic resonance imaging, and immunoscintigraphy have become standards for the diagnosis of rectal disease, staging of neoplasia, and survey of therapeutic results. The indications, limitations, and relative costs of current imaging methods are reviewed, and advances in imaging technology that promise future benefits to colorectal surgeons are introduced.

Diagnostic and therapeutic applications of monoclonal antibodies in colorectal cancer

PURPOSE

The study contained herein was undertaken to review and summarize the current literature on diagnostic and therapeutic applications of monoclonal antibodies in colorectal cancer.

RESULTS

Limitations of traditional imaging techniques have encouraged development of targeted imaging strategies using radiolabeled monoclonal antibodies. Diagnostic immunoscintigraphy can detect lesions not identified by conventional imaging modalities, although it has not proven useful in the management of primary colorectal cancers and in hepatic metastases. Immunoscintigraphy shows promise in cases of local recurrence and rising carcinoembryonic antigen values; however, the impact of immunoscintigraphy on clinical outcomes and cost-effectiveness remains unproven. Radioimmunoguided surgery has been advocated as a method of more accurately detecting tumor extension and accomplishing radical resection. The technique remains controversial, and its use is not widespread. With respect to therapeutic applications, immunotherapy has most often been investigated in the setting of advanced stage disease. Results in this setting have been poor. In contrast, adjuvant immunotherapy after resection of Dukes C carcinoma has achieved convincing results, with improvements in survival comparable with that of adjuvant chemotherapy. Adjuvant trials are now under way to examine the effectiveness of monoclonal antibodies in the postoperative treatment of early-stage (II) tumors and the combination of monoclonal antibodies and chemotherapy in advanced-stage (III) tumors. Bispecific antibodies, or immunoconjugates with cytokines or toxins, represent additional areas of interest and future investigations.

CONCLUSIONS

At present, immunoscintigraphy is not sufficient to determine, by itself, resectability of colorectal tumor and has limited usefulness in select cases of recurrent cancer and possibly in cases of rising carcinoembryonic antigen values. Immunotherapy with monoclonal antibodies as a postoperative adjuvant treatment shows promise and is currently being investigated in national trials.

Preoperative and postoperative imaging for colorectal cancer

Management and survival in colorectal cancer are dictated by the extent of the disease at the initial diagnosis. Technological advances over the past 25 years have improved the ability to accurately preoperatively stage these lesions and detect recurrence. This article reviews the focus on the utility of computerized tomography, magnetic resonance, endoscopic ultrasound, and newer imaging methods including PET scan and monoclonal antibodies in the management of colorectal carcinoma.

Radiolabelled monoclonal antibodies in tumour imaging and therapy: out of fashion?

The initial enthusiasm for the development of diagnostic and therapeutic studies involving the use of monoclonal antibodies was replaced by scepticism as hopes remained unfulfilled. Against this background one needs to ask whether immunoscintigraphy (IS) serves clinical needs effectively and whether radioimmunotherapy (RIT) has a future. The current review considers these questions by reference to relevant studies. Taking colorectal cancer as an example, an appraisal is offered of the ability of IS to detect disease at an early stage and thereby to reduce mortality, and of the influence of the results of IS on patient management. It is concluded that in a limited number of cases of colorectal cancer and other solid tumors, IS will allow surgery to be performed at a stage where cure is still possible because of its ability to detect early recurrence. Turning to RIT, the results of studies in respect of various tumour types are reviewed, with due attention to reported toxicity. As regards colorectal cancer, no consistent therapeutic effects have been achieved, and myelotoxicity is typically the dose-limiting factor. Thus many questions remain to be answered, regarding antigens to be targeted, fractionation schedule, the use of "humanised" antibodies, choice of radionuclide and the use of intact immunoglobulins or fragments. These questions are considered. Overall it is concluded that the most promising application of RIT is as adjuvant therapy in patients with minimal residual disease, and a controlled multicentre trial is recommended. The development of more potent radio-immunoconjugates for therapeutic and ultimately diagnostic purposes will contribute to the improvement and development of IS by increasing its potential to influence prognosis.