Use of an In Vivo Biotinylated Single-Chain Antibody as Capture Reagent in an Immunometric Assay to Decrease the Incidence of Interference from Heterophilic Antibodies

Background: Heterophilic antibodies are a common source of interference in immunometric assays. We tested the hypothesis that the incidence of such interference could be decreased by use of a recombinant in vivo-biotinylated single-chain antibody (scFv) as the capture reagent.

Methods: We established three assays for carcinoembryonic antigen (CEA) with the capture antibody either chemically biotinylated whole monoclonal T84.66 immunoglobulin, a corresponding F(ab′)2 fragment, or a site-specifically biotinylated T84.66-derived single-chain antibody (scFv). Antibodies were attached to streptavidin-coated microplates. A common europium-labeled anti-CEA tracer monoclonal antibody was used. The F(ab′)2 assay used a buffer that contained bovine immunoglobulin and aggregated irrelevant monoclonal antibody MAK33 as blocking agents. The whole T84.66 immunoglobulin and scFv assays were performed without addition of blocking agents. From a previous study of 11 261 sera, we tested 390 samples that had displayed heterophilic antibody interference and 179 samples that had not.

Results: After correction for bias and analytical variation [2.56 × SD (from the precision profile)], 383 samples displayed significantly different values (>1 μg/L) in the whole T84.66-based assay and the F(ab′)2 assay. In contrast, only nine samples showed falsely high CEA concentrations in the scFv assay. After blocking agents were added to the assay buffer, eight of the nine samples displayed results equivalent to those of the F(ab′)2 assay, and sample dilution produced equivalent results for the remaining sample.

Conclusion: Their ability to be site-specifically biotinylated and their relative resistance to heterophilic antibody interference indicate that single-chain antibodies may be useful solid-phase reagents in immunometric assays.

Human heterophilic antibodies display specificity for murine IgG subclasses

OBJECTIVES

The study investigated heterophilic antibodies: the human immunoglobulin classes involved and their specificity for different murine IgG subclasses.

DESIGN AND METHODS

Using immunofluorometric assays for human IgA, IgM and IgG binding murine IgG1, we analyzed 173 samples displaying positive interference and 97 negative control samples from a previous study. We also set up assays for heterophilic antibody interference using Mabs from different murine IgG subclasses. Three Mabs each of murine IgG1, IgG2a and IgG2b subclasses, one murine IgG3 Mab and one rat Mab were used.

RESULTS

Elevated levels of human murine IgG1-binding immunoglobulins of IgM class only were found in 40% of interference-positive samples, human IgG only in 1.7%, and human IgA only in 2.3% of the samples. Both elevated human IgG and IgM classes were found in 3.5% of the samples, IgA and IgM in 4.0%, and finally, all three immunoglobulin classes in 1.7% of the samples. Eighty percent of interference positive samples showed heterophilic assay interference for at least one murine IgG1 Mab, 35% for IgG2a, 66% for IgG2b, 52% for IgG3a and 17% for the rat Mab.

CONCLUSIONS

Heterophilic antibody interference is mainly caused by IgM class human antibodies with a marked murine IgG subclass specificity. Combining assay antibodies from different murine IgG subclasses may reduce interference in immunoassays.

Pharmaceutical-grade albumin: impaired drug-binding capacity in vitro

Background

Albumin is the most abundant protein in blood plasma, and due to its ligand binding properties, serves as a circulating depot for endogenous and exogenous (e.g. drugs) compounds. Hence, the unbound drug is the pharmacologically active drug. Commercial human albumin preparations are frequently used during surgery and in critically ill patients. Recent studies have indicated that the use of pharmaceutical-grade albumin is controversial in critically ill patients. In this in vitro study we investigated the drug binding properties of pharmaceutical-grade albumins (Baxter/Immuno, Octapharma, and Pharmacia & Upjohn), native human serum, and commercially available human serum albumin from Sigma Chemical Company.

Methods

The binding properties of the various albumin solutions were tested in vitro by means of ultrafiltration. Naproxen, warfarin, and digitoxin were used as ligands. HPLC was used to quantitate the total and free drug concentrations. The data were fitted to a model of two classes of binding sites for naproxen and warfarin and one class for digitoxin, using Microsoft Excel and Graphpad Prism.

Results

The drugs were highly bound to albumin (95–99.5%). The highest affinity (lowest K₁) was found with naproxen. Pharmaceutical-grade albumin solutions displayed significantly lower drug-binding capacity compared to native human serum and Sigma albumin. Thus, the free fraction was considerably higher, approximately 40 times for naproxen and 5 and 2 times for warfarin and digitoxin, respectively. The stabilisers caprylic acid and N-acetyl-DL-tryptophan used in the manufacturing procedure seem to be of importance. Adding the stabilisers to human serum and Sigma albumin reduced the binding affinity whereas charcoal treatment of the pharmaceutical-grade albumin from Octapharma almost restored the specific binding capacity.

Conclusion

This in vitro study demonstrates that the specific binding for warfarin and digitoxin is significantly reduced and for naproxen no longer detectable in pharmaceutical-grade albumin. It further shows that the addition of stabilisers may be of major importance for this effect.

Testing and validating a homogeneous immunometric assay for interference

We analyzed 95 sera, demonstrating interference in a previous study, with the Kryptor homogeneous time-resolved fluorescence resonance energy transfer carcinoembryonic antigen (CEA) immunoassay (Brahms AG, Berlin, Germany). Only one serum differed, i.e., 6.0 μg/l for Kryptor vs. 13.3 μg/l for a microtiter plate in-house immunofluorometric assay (IFMA), using both aggregated mouse immunoglobulins as blocker and capture monoclonal antibody (Mab) F(ab′)

Kryptor-CEA assay results thus agreed with our inhouse CEA assay results, showing no interference. As the Kryptor-CEA assay antibodies were sensitive to interference and the Kryptor-CEA assay buffer did not reduce interference as efficiently as our in-house assay buffer, the Kryptor-CEA assay format was crucial for the absence of interference.

A single-chain-Fv-based immunofluorometric assay specific for the CEA variant NCA-2

Carcinoembryonic antigen (CEA) is a member of the immunoglobulin gene superfamily. In meconium, a C-terminal truncated form of CEA, denominated NCA-2, is predominant. This molecular variant is present also in sera from adult cancer patients, but no NCA-2-specific assay is yet available, and its possible clinical significance is largely unknown. We have used phage display technology to produce a single-chain antibody (scFv) suitable for an NCA-2-specific assay and compared the NCA-2 results with CEA values in patient sera. A phagemid library with a diversity of 10(7) was constructed from splenic mRNA obtained from a mouse immunized with NCA-2 purified from human meconium. Following phage rescue and three rounds of panning on solid phases coated with NCA-2, several clones were isolated, which displayed high specificity for NCA-2. These were sub-cloned into an Escherichia coli expression vector for high-level expression of soluble scFv. From BIAcore studies a single scFv with low k(off) and a K(D) of 10(-10) mol/l was selected for europium labelling and an immunofluorometric assay with a sensitivity of 0.2 microg/l was established. The assay detects a protein in serum with a molecular weight significantly lower than CEA. For comparison, a routine assay for CEA, which measures both CEA and NCA-2 equivalently, and a CEA-specific assay based on the T84.66 antibody were employed. The difference between serum values measured with the two CEA assays corresponded to the values determined with the NCA-2-specific assay.

Protein epitopes in carcinoembryonic antigen. Report of the ISOBM TD8 workshop

To characterize antigenic sites in carcinoembryonic antigen (CEA) further and to investigate whether there are differences between colon tumor CEA and meconium CEA (NCA-2) that can be detected by anti-CEA monoclonal antibodies (MAb), 19 new anti-CEA MAb were analyzed with respect to specificity, epitope reactivity and affinity. Their reactivities were compared with 10 anti-CEA MAb with known CEA-domain binding specificity that have previously been classified into five nonoverlapping epitope groups, GOLD 1-5. Cross-inhibition assays with antigen-coated microtiter plates and immunoradiometric assays were performed in almost all combinations of MAbs, using conventionally purified CEA (domain structure: N-A1B1-A2B2-A3B3-C) from liver metastasis of colorectal carcinomas, recombinant CEA, meconium CEA (NCA-2), truncated forms of CEA and NCA (CEACAM6) as the antigens. The affinity of the MAbs for CEA was also determined. The new MAbs were generally of high affinity and suitable for immunoassays. Three new MAbs were assigned to GOLD epitope group 5 (N-domain binding), 3 MAbs to group 4 (A1B1 domain), 1 to group 3 (A3B3 domain), 3 to group 2 (A2B2 domain) and 3 to group 1 (also the A3B3 domain). Three MAbs formed a separate group related to group 4, they were classified as GOLD 4' (A1B1 domain binding). The remaining 3 MAbs appear to represent new subspecificities with some relationship to GOLD groups 1, 2 or 4, respectively. Five MAbs, all belonging to epitope group 1 and 3, reacted strongly with tumor CEA but only weakly or not at all with meconium CEA, demonstrating that the two products of the CEA gene differ from each other, probably due to different posttranslational modifications.

Immunometric assay interference: incidence and prevention

BACKGROUND

The primary aim of the study was to reduce interference in an in-house two-site, two-step immunometric assay.

METHODS

In the running laboratory routine, 11 261 samples were tested with a carcinoembryonic antigen (CEA) assay with bovine immunoglobulin but no murine immunoglobulins in the buffer, in parallel to our routine CEA assay, using 15 mg/L heat-treated nonspecific murine immunoglobulin (MAK33) in the buffer and with the Fc fragments removed from the capture antibody.

RESULTS

The frequency of interference was estimated to be 4.0% (95% confidence interval, 3.3-4.7%). The addition of 15 mg/L native MAK33 had little effect (frequency, 3.9%; 95% confidence interval, 3.2-4.6%), whereas adding 15 mg/L heat-treated MAK33 reduced interference to 0.86% (0.61-1.12%), and adding 50 mg/L reduced it further to 0.06% (0-0.13%). Removing the Fc fragments by itself reduced interference to 0.10% (0.02-0.19%). There were no statistically significant differences for age (P <0.23) or gender (P <0.40) between patients with interference (n = 210) and a randomly selected interference-negative control group (n = 186). Interference was not constant in patients: 15 of 25 individuals positive for interference and with four or more samples screened for interference had an interference-negative sample either before or after the peak of interference.

CONCLUSIONS

In a two-site, two-step immunometric assay using mouse monoclonal antibodies, use of heat-treated nonspecific murine immunoglobulin in the buffer or removal of the Fc fragment from the capture antibody could improve performance.

Immunometric Assay Interference

Background: The primary aim of the study was to reduce interference in an in-house two-site, two-step immunometric assay.

Methods: In the running laboratory routine, 11 261 samples were tested with a carcinoembryonic antigen (CEA) assay with bovine immunoglobulin but no murine immunoglobulins in the buffer, in parallel to our routine CEA assay, using 15 mg/L heat-treated nonspecific murine immunoglobulin (MAK33) in the buffer and with the Fc fragments removed from the capture antibody.

Results: The frequency of interference was estimated to be 4.0% (95% confidence interval, 3.3–4.7%). The addition of 15 mg/L native MAK33 had little effect (frequency, 3.9%; 95% confidence interval, 3.2–4.6%), whereas adding 15 mg/L heat-treated MAK33 reduced interference to 0.86% (0.61–1.12%), and adding 50 mg/L reduced it further to 0.06% (0–0.13%). Removing the Fc fragments by itself reduced interference to 0.10% (0.02–0.19%). There were no statistically significant differences for age (P &lt;0.23) or gender (P &lt;0.40) between patients with interference (n = 210) and a randomly selected interference-negative control group (n = 186). Interference was not constant in patients: 15 of 25 individuals positive for interference and with four or more samples screened for interference had an interference-negative sample either before or after the peak of interference.

Conclusions: In a two-site, two-step immunometric assay using mouse monoclonal antibodies, use of heat-treated nonspecific murine immunoglobulin in the buffer or removal of the Fc fragment from the capture antibody could improve performance.

Epitope mapping and affinity estimation of 83 antibodies against prostate-specific antigen

Eighty-three antibodies submitted to the ISOBM TD-3 Workshop on prostate-specific antigen (PSA) were characterized by cross-inhibition studies, immunometric assay and affinity estimation with free or complexed PSA (PSA-alpha1-antichymotrypsin, PSA-ACT). Nine antibodies did not bind PSA or PSA-ACT when coated onto microtiter plates or in solution. Another 3 antibodies bound the antigens only when in solution and were therefore omitted from the cross-inhibition experiments. Dissociation constants (Kd) were estimated from the concentration of free antibody needed to achieve half-maximal binding of the antigen. Kd values for PSA and PSA-ACT ranged from 2 x 10(-12) to >10(-8) mol/l. Antibodies were classified into 6 main groups according to their reactivity. Group 1 comprised 15 antibodies (#25, 26, 33, 68, 73, 77, 78, 80, 85, 209, 213, 216, 223, 230, and 262) specific for free PSA. These antibodies had >80% cross-inhibition and showed high affinity for PSA with minimal or no affinity for the PSA-ACT complex. Group 2 comprised antibodies that reacted with both free PSA and PSA-ACT. Three subgroups were defined: group 2a (#40), group 2b (#32) and group 2c (#35, 37, 63, 90, 215 and 226). Group 3a antibodies (#31, 36, 37, 57, 64, 66, 72, 82, 84, 212, 224, 229, 257 and 260) were closely related to those of group 2, with two exceptions in group 3b (#88 and 89). Group 4 contains antibodies with binding patterns similar to those represented by groups 3b and 6b. These antibodies could be divided into two subgroups: group 4a (#30, 38, 51, 217, and 220) and group 4b (#74). Group 5 was more heterogeneous, with distinct inhibition patterns: group 5a (#50, 54, 76, 81,207, and 222); group 5b (#41), and group 5c (#28 and 86). Group 6 antibodies bind epitopes on both free PSA and PSA-ACT, but have epitopes unrelated to those represented in groups 1-3: group 6a contains 15 antibodies (#24, 27, 29, 34, 55, 56, 65, 79, 210, 214, 218, 221, 225, 258 and 261), and group 6b 2 antibodies (#67 and 75). These 6 groups represent the major immunodominant regions, one of which is exposed only on free PSA. Our classification could provide a useful guide in choosing antibodies for future PSA assays.

Summary report of the TD-3 workshop: characterization of 83 antibodies against prostate-specific antigen

Twelve research groups participated in the ISOBM TD-3 Workshop in which the reactivity and specificity of 83 antibodies against prostate-specific antigen (PSA) were investigated. Using a variety of techniques including cross-inhibition assays, Western blotting, BIAcore, immunoradiometric assays and immunohistochemistry, the antibodies were categorized into six major groups which formed the basis for mapping onto two- and three-dimensional (2-D and 3-D) models of PSA. The overall findings of the TD-3 Workshop are summarized in this report. In agreement with all participating groups, three main antigenic domains were identified: free PSA-specific epitopes located in or close to amino acids 86-91; discontinuous epitopes specific for PSA without human kallikrein (hK2) cross-reactivity located at or close to amino acids 158-163; and continuous or linear epitopes shared between PSA and hK2 located close to amino acids 3-11. In addition, several minor and partly overlapping domains were also identified. Clearly, the characterization of antibodies from this workshop and the location of their epitopes on the 3-D model of PSA illustrate the importance of selecting appropriate antibody pairs for use in immunoassays. It is hoped that these findings and the epitope nomenclature described in this TD-3 Workshop are used as a standard for future evaluation of anti-PSA antibodies.

Specificity and affinity of 30 monoclonal antibodies against alpha-fetoprotein

Twenty-two antibodies with high affinity for AFP could be classified into groups according to five AFP binding regions, designated A-E, based on cross-inhibition studies and immunometric assay combinations. Antibodies in group A (ISOBM TD2 No. in parentheses): H31 (119), AFP-4-F45 (111), 140/5 (117), K51 (99), K52 (110), AFP-200014A (120) and F2 (118) and in group B: A4-4 (98) and AFP-4-F67 (93) were only inhibited by antibodies belonging to the same groups and could be used in immunometric assay combinations with all other antibodies. Groups C, D and E were inhibited by antibodies in adjacent antibody groups and did not form immunometric assay pairs with antibodies belonging to neighboring groups. Group C comprises: K28 (105), A34-B/B5 (101), AFP-4-F111 (95), AFP100025B (121) and K57 (116), group D: E7 (114) and D10 (92) and group E: H219 (115), K6B1 (103), A34-A/D12 (104), C2 (102), C9 (94) and C10 (97). For six of seven antibodies with low binding to labelled AFP, the specificity could not be determined. Two antibodies were not conclusively assigned to any binding region. Antibody 9A12 (109) may be classified into group E based on immunometric assay combinations, but could not be evaluated in cross-inhibition experiments due to low binding to labelled AFP. Antibody 19F12 (100) functioned as a tracer antibody in combination with all other antibodies, but did not bind AFP when used as solid phase antibody. This antibody could therefore represent a unique binding specificity.

Stability of free and total prostate specific antigen in serum from patients with prostate carcinoma and benign hyperplasia

PURPOSE

Instability of prostate specific antigen (PSA) in serum might complicate the interpretation of the free-to-total PSA ratio. We studied the in vitro stability of free PSA and total PSA in serum of patients with prostate cancer or benign prostate hyperplasia (BPH), and of elderly men without known prostate disease. Furthermore, we investigated conditions to stabilize the in vitro values in serum.

MATERIALS AND METHODS

The effects of storage at 4C on free and total PSA were investigated in serum of 32 men with prostate cancer, 25 with BPH and 29 older than 70 years. All had total PSA less than 25 microg./l. The influence of total PSA levels on in vitro changes in free-to-total PSA was studied in serum of 39 other prostate cancer patients (total PSA 1.7 to 298 microg./l.). Stabilization studies were performed in yet another series of samples from 54 prostate cancer patients (total PSA 1.3 to 238 microg./l.) by adjustment of serum pH to 5.5 before storage. Free and total PSA was measured by a commercial immunofluorometric assay, as well as by in-house immunofluorometric assays. Statistical analyses of the results were performed by analysis of variance with repeated measures.

RESULTS

We found no difference between the results obtained by the 2 assay systems. After 7 days at 4C there was a slight decrease in total PSA in sera of prostate cancer patients, BPH patients and men older than 70 years. A decrease in mean free PSA values occurred in all groups (21.3, 15.7 and 14.6%, respectively). The decrease of free PSA with time was significant (p <0.0001) in all groups but there was no significant difference among the groups (p=0.16). The concomitant decrease in free-to-total PSA ratio was significant in all groups (p <0.0001). This change was group dependent (p=0.003), with the largest decrease in the prostate cancer group. Large interindividual differences were observed. Storage at 4C for 7 days of sera of 39 patients with localized and disseminated prostate cancer (total PSA 1.7 to 298 microg./l.) gave a more pronounced decrease in free PSA than in total PSA. Adjustment of serum pH to 5.5 had a stabilizing effect on free PSA and on the free-to-total PSA ratio, giving a significantly smaller change in both values (p <0.0001).

CONCLUSIONS

In vitro instability of free PSA in serum and large interindividual differences should be considered when using the ratio of free-to-total PSA in evaluation of patients with suspected prostate cancer. Serum samples should be stored frozen if not analyzed immediately or acidified to pH 5.5. Interpretation of data from determination of free-to-total PSA ratio should be done with caution if the sampling and storage conditions are not known.

Fecal calprotectin concentration in patients with colorectal carcinoma

PURPOSE

The study contained herein was undertaken to investigate fecal calprotectin excretion in a series of patients with colorectal carcinoma and to determine whether the excretion was influenced by localization or stage of the tumor. Furthermore, the effect of surgical treatment on the concentrations was studied. Fecal calprotectin was also compared with plasma concentrations of calprotectin, carcinoembryonic antigen, and C-reactive protein.

METHODS

Fecal calprotectin was measured in 119 consecutive patients admitted for treatment of colorectal carcinoma. In 116 (97.5 percent) patients, resectional surgery was performed. Plasma calprotectin was measured in 90 (76 percent) patients, carcinoembryonic antigen in 88 (74 percent) patients, and C-reactive protein in 82 (69 percent) patients.

RESULTS

Median fecal calprotectin concentration in the 119 patients was 50 (range, 2-950) mg/l, which was significantly (P < 0.0001) higher than in 125 control patients (median, 5.2 mg/l). In 23 patients studied also after resection, the excretion fell greatly. There were no significant differences in fecal calprotectin concentration among patients with different tumor stages. Elevated plasma calprotectin concentrations were found in 67 of 90 (73.3 percent) patients with colorectal carcinoma, compared with elevated fecal calprotectin in 111 of 119 (93.3 percent) patients, and there was no significant correlation between plasma and fecal calprotectin concentrations. Plasma calprotectin concentrations were significantly lower in patients with T1 or T2 tumors than in those with more advanced stages (P = 0.0025).

CONCLUSION

Measurement of fecal calprotectin may become a diagnostic tool in detecting colorectal carcinoma. The specificity in relation to colorectal carcinoma has not, however, been completely investigated. Both neoplastic and inflammatory conditions may be associated with elevated values; therefore, it is unlikely that calprotectin can predict specific colonic disorders.

Specificity and affinity of 26 monoclonal antibodies against the CA 125 antigen: first report from the ISOBM TD-1 workshop. International Society for Oncodevelopmental Biology and Medicine

The specificity of 26 monoclonal antibodies against the CA 125 antigen was investigated in two phases of the ISOBM TD-1 workshop. The binding specificity was studied using CA 125 immunoextracted by specific antibodies immobilized on various solid phases, or on the surface of human cell lines. Immunometric assays using all possible antibody combinations were used to study the topography of antibody binding sites on the antigen. We conclude that the CA 125 antigen carries only two major antigenic domains, which classifies the antibodies as OC125-like (group A) or M11-like (group B). One antibody, OV 197, showed binding specificity related to some of the OC125-like antibodies, but was classified into a separate group C. The OC125-like group of antibodies has four subgroups with different binding specificities. These are A1 = OC 125 and K 95, A2 = K 93, A3 = B43.13, and A4 = ZS 33, B27.1 and CCD 247. Binding of nonlabelled OC 125 or K 95 to CA 125 caused a marked increase in binding of labelled OV 197 to the complex. This conformational change was not observed with any other antibody combinations. Antibody B43.13 could form immunometric assay combinations particularly with antibodies of subgroup A4, indicating that the B43.13 epitope is in the periphery of the binding area of OC125-like antibodies. The M11-like group of antibodies is more homogenous with strong cross-inhibition between most antibodies. Only one antibody, ZR 38, would form an immunoassay combination with other M11-like antibodies and thus represents a distinct subgroup. The main group of M11-like antibodies are M 11, ZR 45, MA602-6, K 91, OV 185, K 101, K 90, K 96, K 97, K 102, CCD 242, 145-9, and 130-22. Antibody OV 197 binds to a domain designated C and is unique, as stated above. Antibody pairs from any two of the three groups may be used in immunometric assays. Three antibodies were not studied by complete cross-inhibition due to low affinity (OV 198 and K 100) or lack of material (MA602-1). OV 198 and K 100 are most likely OC125-like and MA602-1 is M11-like. Antibody affinity was estimated with labelled antigen in solution or with antigen absorbed on microtiter wells. Western blot analysis showed staining both in the stacking gel and corresponding to a molecule of 200 kDa. There was a marked difference between the antibodies in their ability to bind to CA 125 immobilized on a membrane. Strongest binding was observed with the M11-like antibodies, particularly M 11, K 96, K 97, MA602-6, 145-9. Antibodies belonging to the subgroup A4 were the only OC 125-like antibodies which reacted well with CA 125 in Western analysis. Digestion of CA 125 with proteolytic enzymes showed it to be particularly sensitive to trypsin cleavage. However, no low molecular weight fragments with preserved immunoreactivity were found.

[Tumor marker analyses--valuable tools if used correctly]

The tumour marker assays in routine use today are not cancer-specific. Most markers are normal products of epithelial tissues, usually excreted from the intact organ. The infiltrating malignant growth allows release directly into lymph and blood, where the product is measured as a "tumour marker". Many tumour markers are glycoproteins depending on the liver function for their catabolism. These mechanisms explain the slight to moderate increases in tumour marker values found in various non-malignant diseases. Therefore, in general, such assays are of no use for screening healthy populations, and a normal value does not exclude cancer. Their main use is in the primary staging of patients known to have cancer, to evaluate the completeness of primary surgery, to follow-up patients for early detection of relapses, and to monitor the effect of cytotoxic or radiation therapy of advanced disease. In all these applications, good clinical judgement is the necessary basis for using these assays.

Serum CA 125 level allows early identification of nonresponders during induction chemotherapy

CA 125 was measured during induction chemotherapy in 119 patients with advanced epithelial ovarian cancer who had residual disease after primary surgery in order to determine whether patients with poor response to further treatment could be identified during early chemotherapy. All patients had a prechemotherapy serum CA 125 level higher than 35 U/ml. Blood samples were further obtained 4 weeks after the first, second, and third course. Four weeks after the second course of chemotherapy, all 20 patients with PCR, or microscopic disease at second-look, all 17 who achieved complete clinical remission, and 36 of 40 who achieved partial remission had serum CA 125 of 65 U/ml or less or had a decrease of 50% or more of the prechemotherapy level. Survival analysis showed that patients with a serum CA 125 level of 65 U/ml or less 4 weeks after the second course of chemotherapy had the best prognosis. In patients with a serum CA 125 level higher 65 U/ml at that time, a decrease of 50% or more of the prechemotherapy level indicated a prognosis better than that with a lesser decrease. The combined criteria for serum CA 125 (level > 65 U/ml 4 weeks after the second course and a decrease < 50% of the prechemotherapy level) allowed for identification of a real high-risk group with a median survival of 8.9 months and was identified by Cox regression multivariate analysis as the most powerful indicator for survival (P < 0.0001).

Is serum CA 125 at the time of relapse a prognostic indicator for further survival prognosis in patients with ovarian cancer?

The prognostic significance of serum CA 125 level before treatment of relapse for invasive epithelial ovarian cancer has been evaluated in 135 patients. At time of relapse, serum CA 125 level was higher than 35 U/ml in 110 (82%) patients. Those with serum CA 125 level of 35 U/ml or less at relapse had a better prognosis than those with higher values. Among patients with serum CA 125 level higher than 35 U/ml no difference in survival was observed. By multivariate analysis the independent prognostic factors for survival were histologic type (P < 0.0001) and serum CA 125 level (P < 0.01). Randomized trials are needed to further evaluate whether early detection of disease relapse because of serial serum CA 125 measurements does have prognostic significance.

Circulating secretory component in relation to early diagnosis and treatment of liver metastasis from colorectal carcinomas

AIMS

To evaluate serum secretory component in relation to early detection and clinical management of liver metastasis in patients with colorectal cancer.

METHODS

Secretory component and carcinoembryonic antigen (CEA) were analysed in serial serum samples from 23 patients who had liver metastases as the only apparent recurrence, and in sera from 54 matched controls. Results of surgical treatment of recurrences were classified peroperatively as radical when no residual tumour was apparent and resection margins were free of disease.

RESULTS

In total, 18 (78%) patients had increased secretory component during the whole follow up period (median 16 months); 12 (52%) had raised secretory component concentrations before clinical recurrence (median lead time 5.2 months). There was no difference before recurrence between circulating secretory component and CEA in sensitivity and lead times. Seventeen patients underwent surgery for hepatic metastasis; seven had radical hepatic resection of which only two (29%) showed increased secretory component concentrations before clinical recurrence; both had concurrent raised CEA values. By contrast, secretory component was raised in 83% of those cases considered inoperable.

CONCLUSIONS

Although serum secretory component clearly increases in most patients with liver metastases, its clinical value seems questionable because secretory component apparently indicates mainly inoperable hepatic metastases.

Prognostic value of pre- and postoperative serum CA 125 levels in ovarian cancer: new aspects and multivariate analysis

The prognostic significance of the serum CA 125 level was studied in 687 patients with invasive epithelial ovarian malignancies. The samples were collected preoperatively in 200 and postoperatively in 487 patients. Median follow-up was 27 months (range 3-84). The serum CA 125 level was elevated preoperatively in 90% of cases, with a median value of 429 U/mL. In patients with evidence of disease at the time of sampling, the CA 125 serum level correlated directly to tumor stage, tumor load, and histologic grade. Using Cox multivariate analysis, the preoperative serum CA 125 level had no independent prognostic significance, whereas the postoperative level did. In patients without residual disease after primary surgery, histologic type (P less than .0001), postoperative CA 125 level with 35 U/mL as the cutoff value (P = .0009), and tumor grade (P = .034) were independent prognostic factors for survival. For those with residual tumor after primary surgery, histologic type (P less than .0001), postoperative treatment (P = .0002), size of residual disease (P = .0005), and postoperative serum CA 125 level with 65 U/mL as a cutoff (P = .003) were independent prognostic factors.

CA 125 measured before second-look laparotomy is an independent prognostic factor for survival in patients with epithelial ovarian cancer

The prognostic significance of serum CA 125 level measured in the week before second-look operation was evaluated in 208 patients with invasive epithelial ovarian cancer. Serum CA 125 level was greater than 35 U/ml in 44.7% of patients. All patients with pathological complete response (PCR) had a serum CA 125 level less than or equal to 35 U/ml except one who developed lung metastases 2 months later. The sensitivity of serum CA 125 for identifying residual tumor at second-look operations was 58%, the specificity was 98%, the predictive value of a positive test was 99%, and the predictive value of a negative test was 43%. By Cox regression analysis, tumor state of second look, serum CA 125 level, histologic type, FIGO stage, and tumor grade were identified as independent prognostic factors for survival. We conclude that measurement of serum CA 125 level after induction chemotherapy represents a noninvasive method to identify patients at high risk for subsequent death from ovarian cancer. As far as we know, this is the first report to identify serum CA 125 level as an independent prognostic factor at the time of second-look laparotomy.

CA125 in peritoneal fluid of ovarian cancer patients

The presence of CA125 was assessed in peritoneal fluid from 70 patients with ovarian cancer and 32 control patients. The follow-up period ranged from 39 to 89 months (median, 56 months). The cutoff for normal peritoneal fluid CA125 levels was determined to be 250 U/ml. A positive correlation between the serum and peritoneal fluid CA125 levels was observed (P less than 0.001). Peritoneal fluid levels were higher than serum levels in all patients. Patients with evidence of active ovarian cancer showed higher peritoneal fluid CA125 levels than the control patients (P less than 0.001). Peritoneal fluid CA125 levels correlated inversely with survival (P = 0.004). The peritoneal fluid CA125 levels were higher in patients with bulky tumor than in those with small (less than 1 cm) tumors (P less than 0.001). Eight out of twenty-six patients with active cancer and available peritoneal cytology had a negative peritoneal cytology. Three of these patients showed elevated peritoneal fluid levels. Three patients out of twenty-four showed elevated peritoneal fluid CA125 levels at second-look laparotomy. These 3 patients had negative biopsies at second-look surgery, but relapsed during the observation period. At second-look laparotomy an elevated peritoneal fluid CA125 level may imply a bad prognosis, but a normal level does not exclude the presence of disease.

CA125 and placental alkaline phosphatase as serum tumor markers in epithelial ovarian carcinoma

Placental alkaline phosphatase (PLAP) was measured by an immunoradiometric assay using the monoclonal antibody C2 (PLAP-C2). Serum samples of 135 patients with epithelial ovarian cancer were analyzed, and the results were compared with CA125 levels. CA125 and PLAP-C2 were elevated in 85 and 43% of the patients, respectively. Only 1 patient with normal CA125 and evidence of disease at the time of sampling had an elevated PLAP-C2. Fifty-three patients with measurable tumor were followed longitudinally during chemotherapy. Correct correlation with disease evolution was observed in 95% of the patients for CA125 and in 59% for PLAP-C2. The PLAP-C2 assay did not add significantly to the predictive value of CA125 in the diagnosis and follow-up of epithelial ovarian cancer.

Carcinoembryonic antigen in anal carcinoma

Patients with squamous cell carcinoma of the anal canal occasionally present with an elevated level of carcinoembryonic antigen (CEA) in serum. The present study was performed to evaluate the clinical importance of this observation. Serum CEA was measured in 106 patients prior to chemo- and radiotherapy and during follow-up. Twenty patients had elevated serum CEA level before treatment. In 6 of 12 cases, serum CEA did not normalize after successful treatment and in 4 of 7 cases it rose no further despite progressive disease. CEA-positive tumours were more often poorly differentiated than CEA-negative tumours. There was no significant correlation between serum CEA, tumour CEA and prognosis. We conclude that measurement of serum CEA and staining of tumour CEA lack clinical importance.

Evaluation of serum CA 125 levels in the monitoring of ovarian cancer

Serum CA 125 levels were evaluated in 227 patients with ovarian cancer. CA 125 levels were elevated in 86% of the patients. All histologic types, including mucinous tumors, were associated with raised CA 125 levels. There was a positive correlation with tumor burden and an inverse correlation with degree of differentiation. In patients undergoing radical operation an elevated CA 125 level was a bad prognostic index. Serial CA 125 measurements were assessable in 112 patients undergoing chemotherapy. Rising or falling levels correlated with disease in 92% of the cases. The CA 125 level increased before clinical progression with a median lead time of 3 months. Only patients who showed objective response to chemotherapy had a decrease in antigen levels of greater than or equal to 30% 4 weeks after the first course of chemotherapy and a normalization of CA 125 levels 3 months after initiation of chemotherapy. Rising levels were always associated with progression. These data suggest that CA 125 may aid in early identification of nonresponders. However, a normal CA 125 level does not exclude the presence of disease.