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Biomedical subjects

G Milano

Publications and source records attributed to G Milano.

At least 109 records · Page 6Linked to original sources
PubMed1996

Histological analysis of the coracoacromial arch: correlation between age-related changes and rotator cuff tears.

The purpose of this study was to analyze age-related changes in the coracoacromial arch and correlate these degenerative changes with rotator cuff tears. We obtained 80 shoulders from 40 cadavers. The mean age at death was 58.4 years. We performed a gross examination of the rotator cuff and the acromion and histological examination of the coracoacromial ligament. The statistical significance of any difference for each group considered was determined by Student's t-test. The rotator cuff was normal in 66 specimens; there was an articular-side partial tear in 4 cases, a bursal-side partial tear in 6 cases, and a full-thickness tear in 4 cases. Age was correlated with increasing incidence and severity of cuff tears. We noted age-related degenerative changes in the coracoacromial ligament, degeneration of the acromial bone-ligament junction, and acromial spur formation. Anterior acromial spur was not related to the morphology of the acromion. We observed an increased incidence of bursal-side and complete cuff tears when the acromion was curved or beaked. Degenerative changes in the undersurface of the acromion were also present when the rotator cuff was normal. Bursal-side and complete cuff tears were associated with severe degenerative changes in the acromion in 100% of cases. Articular-side cuff tears were not related either to acromial morphology or degenerative changes in the coracoacromial arch. The association between cuff tears and acromial spur was more evident in the presence of a type III acromion. Our results would suggest that the incidence and severity of rotator cuff tears are correlated with aging and with the morphology of the acromion. Rotator cuff tears that involve the bursal side are often associated with changes in the coracoacromial ligament and the undersurface of the acromion. However, degenerative changes in the coracoacromial arch are always related to aging, also in the presence of a normal rotator cuff. Articular-side partial tears do not cause damage to the undersurface of the acromion.

Acromioclavicular Joint↗
PubMed1996

Critical factors for optimizing the 5-fluorouracil-folinic acid association in cancer chemotherapy.

BACKGROUND: The 5-fluorouracil (FU)-folinic acid (FA) association has demonstrated clinical efficacy in colorectal cancer, both in adjuvant and metastatic situations. However, there is no clear consensus about the optimal FU-FA schedule and dose. In addition, it would be of interest to identify FU-FA-responsive tumors. DESIGN: Our purpose was to review preclinical and clinical data dealing with prediction of FU-FA sensitivity and optimization of FU-FA schedules. RESULTS: Preclinical studies have highlighted the importance of thymidylate synthase (TS), the cellular target of the FU-FA mechanism of action, for predicting FU sensitivity. It appears that the more sensitive cell lines express the lowest TS activity. Interestingly, the cell lines sensitive to FA supplementation are those more sensitive to FU. The role of TS in FU-FA responsiveness has been clearly demonstrated in patients with colorectal and gastric cancers. Preliminary in vitro and clinical data have shown that the folylpolyglutamate synthetase (FPGS), the enzyme responsible for folate polyglutamylation, is another promising tool for identifying FU-FA-responsive tumors. So far, results of clinical trials do not form a clear consensus regarding the need to administer high FA doses for improving FU-FA treatment. Experimental studies on human cancer cell lines have demonstrated the wide variability among cell lines, ranging from 0.05 to 200 microns, of 1 FA concentrations required for maximal FU potentiation. In addition, pharmacokinetic studies have reported a significant variability of active folates in plasma after administration of standard-dose FA. Altogether, these observations favour high-dose FA administration to achieve high folate concentrations in plasma and thus to counteract the variability of the 1 FA concentrations required. With respect to the choice of FU-FA schedule, it appears from experimental data that increasing the duration of exposure to FA enhances FU-FA cytotoxicity, probably through an increased formation of reduced folate polyglutamate forms. Considering the S-phase specificity of FU cytotoxicity as well as its rapid elimination from plasma, a schedule of prolonged exposure to both FU and FA should be considered preferable. CONCLUSIONS: Results of the new FU-FA administration schedules such as the one consisting of a 2-hour FA administration followed by a combination of FU bolus and FU infusion, or the chronomodulated FU-FA infusion, open up promising approaches for improving the therapeutic index of FU-FA chemotherapy. Finally, future clinical studies should investigate tumoral parameters pharmacologically linked to FU-FA sensitivity such as pre-treatment TS and FPGS activities. Such tumoral investigations along with FU and FA pharmacokinetic investigations should provide a better understanding of inter-patient variability in response to FU-FA therapy and an optimal management of this chemotherapy regimen.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1996

Individualizing therapy with 5-fluorouracil related to dihydropyrimidine dehydrogenase: theory and limits.

5-Fluorouracil (FU) is metabolized by dihydropyrimidine dehydrogenase (DPD). Patients with suspected or proven DPD deficiency develop more or less severe FU-related side effects including death. In these reported cases, DPD activity in peripheral blood mononuclear cells (PBMC-DPD) was < 100 pmol/min/mg protein. A circadian rhythm in PBMC-DPD activity has been observed, with a peak at 1 a.m. and a trough at 1 p.m. on average. As a corollary, a circadian rhythm was observed in FU plasma concentration, with a peak at 11 a.m. and a trough at 11 p.m. on average. A significant relationship between PBMC-DPD activity and FU clearance was established but the link was weak (r = 0.31). Thus, a FU dose adaptation based on PBMC-DPD is not justified whereas a pharmacokinetically based FU dose adaptation is recommended. Experimental studies have shown that DPD activity in tumor cell lines is related to FU cytotoxicity. Although resistance to FU depends on many factors, recent clinical studies in head and neck cancer patients treated by FU suggest that tumoral DPD activity is a determining factor in predicting FU-responsiveness.

Antimetabolites, Antineoplastic↗
PubMed1996

Link between dihydropyrimidine dehydrogenase activity in peripheral blood mononuclear cells and liver.

Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme of 5-fluorouracil (FU) catabolism, which occurs mainly in the liver. Several cases of severe FU-related toxicity have been reported in patients exhibiting a marked DPD deficiency measured in peripheral blood mononuclear cells (PBMCs). In addition, it has been shown that PBMC-DPD activity correlates to systemic FU clearance. The purpose of the present study was to closely evaluate the link between DPD activity measured in PBMCs and in liver samples obtained from the same patients. This prospective study was conducted on 27 patients (18 men and 9 women) who underwent laparotomy for various pathologies. Liver biopsies were performed in normal liver and immediately stored in liquid nitrogen. Biological liver function tests were within normal values for all patients. Concomitantly to the liver biopsy, a blood sample was taken and PBMCs were immediately isolated and stored at -80 degreesC. Liver-DPD and PBMC-DPD activities were measured by a radioenzymatic assay using 14C-FU as substrate (sensitivity limit, 5 pmol/min/mg protein; interassay reproducibility, 10%). Liver-DPD (mean, 178; median, 186; range, 54-290 pmol/min/mg protein) and PBMC-DPD (mean, 196; median, 205; range, 80-275 pmol/min/mg protein) exhibited the same pattern of distribution. Neither liver-DPD nor PBMC-DPD was significantly different between men and women. A significant linear correlation was demonstrated between liver- and PBMC-DPD activity (liver-DPD = 0.6 x PBMC-DPD + 59, r = 0.56, P = 0.002). Interestingly, the patient who exhibited the lowest PBMC-DPD activity (80 pmol/min/mg protein, at risk value for developing FU-related side effects) also had very low liver-DPD activity (98 pmol/min/mg protein). In conclusion, in patients with normal liver function, DPD activity measured in PBMCs reflects DPD activity expressed in the liver. The demonstrated link between liver- and PBMC-DPD activity reinforces the interest in DPD investigation in PBMCs for selecting, before FU-containing chemotherapy, patients at risk of developing severe toxicities due to impairment of FU clearance.

Adult↗
PubMed1995

Correlation between catalytic activity and protein content for the polymorphically expressed dihydropyrimidine dehydrogenase in human lymphocytes.

A TLC procedure was developed to determine dihydropyrimidine dehydrogenase (DPD) activity in human peripheral lymphocytes. The assay, which used radiolabeled uracil as a substrate, was validated using recombinant pig DPD in which it was demonstrated to yield kinetic constants similar to those found by methods that rely on either spectroscopic determination of NADPH oxidation or HPLC. DPD activity was measured in a group of human lymphocyte extracts, including an extract from a subject that actually presented toxicity to 5-fluorouracil treatment. Measurements of DPD protein content using western immunoblots revealed a significant correlation with activity levels in human lymphocytes. Thus, this correlation could be used to determine not only the levels of expression of this enzyme, which is the cause of an inherited genetic deficiency in pyrimidine catabolism, but also to estimate the degree of sensitivity to pyrimidine-based cancer drugs such as 5-fluorouracil.

Animals↗
PubMed1995

Phase II trial of cisplatin, fluorouracil, and pure folinic acid for locally advanced head and neck cancer: a pharmacokinetic and clinical survey.

PURPOSE: To analyze clinical and pharmacokinetic data of cisplatin (CP)/fluorouracil (FU)/l folinic acid (l FA) chemotherapy administered as first-line treatment to locally advanced head and neck cancer patients. PATIENTS AND METHODS: Thirty-nine patients (35 men and four women; median age, 60 years; six stage III and 33 stage IV) received CP on day 1 (100 mg/m2) followed by l FA (200 mg/m2/d x 5) plus FU (500 mg/m2/d x 5) administered by continuous venous infusion (three cycles planned). Mean plasma concentrations of FU, l FA, and 5-methyltetrahydrofolate (5MTHF) over the cycle were computed. RESULTS: Clinical response was assessable for 33 patients. Response rates on the primary tumor site (n = 33) were 63.7% complete responses (CRs), 24.2% partial responses (PRs), and 12.1% treatment failures. Response rates on lymph nodes (n = 27) were 40.7% CRs, 37.1% PRs, and 22.2% treatment failures. The most frequent toxicity was mucositis (36.2% of cycles grade 3 to 4). Grade 3 to 4 nausea-vomiting, diarrhea, neutropenia, and thrombocytopenia occurred in 6.7%, 1.9%, 13.3%, and 1% of cycles, respectively. Pharmacokinetic analysis showed a wide interpatient variability for both FU (mean, 1.01 mumol/L; range, 0.16 to 2.09), l FA (mean, 1.89, mumol/L; range, 0.52 to 7.88) and 5MTHF plasma concentrations (mean, 3.85 mumol/L; range, 1.30 to 8.11). A significant correlation was demonstrated between FU concentration and hematologic toxicity grade, mucositis grade, and nausea-vomiting/diarrhea grade. Regarding tumor response, patients who failed to respond significantly exhibited lower FU and total folate concentrations than patients with a CR or PR. CONCLUSION: This study highlights the efficacy of CP/FU/l FA in head and neck carcinoma and establishes the clinical importance of coupled FU/FA pharmacokinetics to predict pharmacodynamic variability.

Adult↗
PubMed1995

Response to fluorouracil therapy in cancer patients: the role of tumoral dihydropyrimidine dehydrogenase activity.

PURPOSE: The aim of the present study was to analyze the role of thymidylate synthase (TS; main cellular target of fluorouracil [FU]) and dihydropyrimidine dehydrogenase (DPD; rate-limiting enzyme of FU catabolism) in tumoral biopsies with respect to FU responsiveness. PATIENTS AND METHODS: This prospective study was conducted on 62 head and neck cancer patients (six stage II, 16 stage III, and 40 stage IV). All received first-line chemotherapy with biomodulated FU (5-day continuous infusion). Before treatment, a tumor biopsy and control biopsy (symmetrical nontumoral area) were obtained. Cytosolic TS and DPD activities were measured using radioenzymatic assays. RESULTS: DPD activity was detectable in all samples, without a significant difference between tumoral (median, 60 pmol/min/mg protein; range, 13 to 193) and nontumoral samples (median, 68 pmol/min/mg protein; range, 12 to 150). Tumoral TS and tumoral DPD were not significantly influenced by tumor localization or tumor staging. Among 52 tumors assessable for clinical response, we observed 46% complete responses (CRs), 33% partial responses (PRs), and 21% no responses (NRs). No relationship was demonstrated between TS activity and response to FU therapy. The comparison of tumoral DPD between complete responders and partial or nonresponders showed a trend toward significance (P = .06). In an attempt to reduce variability, we analyzed the tumoral/nontumoral DPD activity ratio; complete responders exhibited a significantly lower normalized DPD than partial or nonresponding patients (median, 0.86, 1.18, and 1.42 for CR, PR, and NR, respectively; CR v PR plus NR, P = .03). CONCLUSION: Although resistance to FU is multifactorial, the present clinical study suggests that FU catabolism in target cells is probably a determinant factor for FU responsiveness in cancer patients and justifies the clinical use of specific DPD inhibitors as FU biomodulators.

Adult↗
PubMed1995

[Increase of dose intensity by pharmacomodulation. General concepts and therapeutic applications].

There are two distinct levels where dose intensity can be increased by pharmacomodulation. The first level implies the inhibition of clearly identified resistance mechanisms. Among them, MDR type resistance is the most studied currently. MDR resistance is mediated by GP170, a cell membrane protein, which can be inhibited by several pharmacological agents like verapamil, ciclosporine and S 9788 which are currently being clinically investigated. The inhibition of DNA repair mechanisms is another approach and a representative example is the inhibition of O6-alkylguanine DNA alkyltransferase by O6-methylguanine or O6-benzylguanine. Modulation of detoxification pathways has also been considered, with for instance, the use of buthionine sulfoximide (BSO) to deplete intracellular glutathione levels. The second level for pharmacomodulation concerns pharmacological interferences with metabolic pathways controlling the activity of anticancer agents and particularly the antimetabolites like ara-C and 5-FU. The use of hydroxyurea or PALA in the case of 5-FU are good illustrations of pharmacomodulation via specific metabolic routes. Finally, the 5-FU-folinic acid combination could characterise a third level of pharmacomodulation where cytotoxic activity is optimised at the site of interaction between activated drug (5FdUMP) and target (thymidilate synthase).

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1995

[Physicochemical compatibility of 5-fluorouracil (new french preparation) and folinic acid].

The potentiation of 5-fluorouracil (5FU) cytotoxicity by folinic acid (FA) is based on strong experimental basis. This experimental concept has been prolonged in the clinical setting where 5FU-FA combination has demonstrated its superiority in comparison to 5FU alone for the chemotherapeutic treatment of advanced colorectal cancer. A justified question concerns the stability for 5FU (new French preparation, with sodium hydroxyde, by Roche)-FA admixtures studied in clinically compatible conditions. We have presently undertaken this study. Based on drug concentrations corresponding to current 5FU-FA chemotherapeutic protocols, we have tested the influence of various factors like the vials, diluents and the type of FA preparation (Lederfoline versus Elvorine). The mixture between 5FU and FA leads to the formation of a precipitate which is influenced by the contact time between 5FU and FA (threshold at 24 hr), by the relative concentration of each drug in mixture and its seems necessary to avoid the mixture between undiluted 5FU and FA (d,1 preparation, Lederfoline). Cassettes or plastic bags are preferable to glass recipients. Finally and above all, the use of pure lFA form (Elvorine) does not lead to the formation of a precipitate seen with the d'1 FA form (Lederfoline) at equal concentration of active folate (1 form). These data carry practical importance for the security and the quality of 5FU-FA protocols and particularly when using portable pumps during prolonged periods necessitating the use of small volume of injectable drug solutions.

Drug Combinations↗
PubMed1995

[Population study of dihydropyrimidine dehydrogenase in cancer patients].

Dihydropyrimidine dehydrogenase (DPD) is the initial enzyme of 5-fluorouracil (5-FU) catabolism. The clinical importance of DPD has recently been demonstrated with the identification of severe and/or lethal 5-FU-related toxicity in patients with suspected or proven DPD deficiency revealed in lymphocytes. We conducted a prospective study on 185 cancer patients in order to evaluate the incidence of complete or partial DPD deficiency. The population comprised 152 men (mean age 62.1) and 33 women (mean age 59.2). Sixty eight were head and neck patients treated by a 5-day continuous infusion of 5-FU (starting dose 1 g/m2/day, with dose adaptation at mid-cycle) for which DPD activity was measured 2-3 days before 5-FU administration (94 cycles analyzed). DPD activity was measured by a radioenzymatic assay using 14C-5-FU. DPD activity showed a unimodal distribution, which globally fits a Gaussian distribution. Mean and median DPD activity were 0.222 and 0.211 nmol/min/mg prot respectively (range 0.065-0.559). No total DPD deficiency was found. Neither liver function nor age influenced DPD activity, but DPD activity was on average 15% lower in women than in men (0.194 and 0.228 nmol/min/mg prot respectively, p = 0.03). In patients treated with 5-FU, the risk of developing side effects was not linked to pretreatment DPD activity. 5-FU-related toxicity was linked to FU systemic exposure. The correlation between DPD activity and FU clearance was weak (n = 90, r = 0.31, p = 0.002). As a corollary, DPD activity in patients requiring a dose reduction was not significantly different from DPD activity in patients who did not require dose modification. From the present study it appears that total DPD deficiency is a very rare event. Although pre-treatment DPD activity cannot be a useful indicator for improving 5-FU dose adaptation strategy, the identification of partial DPD deficiency (< 0.100 nmol/min/mg prot, 3% of the population) could lead to starting the treatment with a markedly reduce 5-FU dose.

Adult↗
PubMed1995

Dihydropyrimidine dehydrogenase: a tumoral target for fluorouracil modulation.

Dihydropyrimidine dehydrogenase (DPD) is the rate-limiting enzyme of 5-fluorouracil (FU) catabolism. Ethynyluracil (776C) is a very potent, mechanism-based irreversible DPD inhibitor that improves the antitumor efficacy and the therapeutic index of FU in laboratory animals. We tested the cytotoxic effects of the FU-776C combination on a panel of 12 human cancer cell lines (4 breast, 4 head and neck, 3 colon, and 1 duodenum). Basal DPD activity (radioenzymatic assay) and FU sensitivity [FU 50% inhibitory concentration (IC50), 3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test] were determined. The FU potentiation by 776C was calculated from the ratio (F) of FU IC50 without 776C divided by FU IC50 with 776C. 776C was not cytotoxic to any of the cell lines tested. On CAL51 cell line expressing a high basal DPD activity, FU enhancement by 776C was a saturable phenomenon related to the 776C concentration; the inhibition of DPD increased between 10(-12) to 10(-6) M of 776C. For the following studies, 776C was tested at 10(-6) M. FU IC50 varied from 15 to 7770 microM among cell lines (median, 390 microM). Basal DPD activity ranged from not detectable (< pmol/min/mg protein) to 320 pmol/min/mg protein among cell lines (median, 53 pmol/min/mg protein). For the 12 cell lines tested, the mean F ranged from 0.7 (no enhancement of FU cytotoxicity by 776C) up to 5.2 and was significantly related to the basal DPD activity: the greater the DPD activity, the greater the FU enhancement factor (Spearman rank correlation, P = 0.019). Enhancement of FU cytotoxicity by 776C occurred only in the six cell lines expressing the greatest basal DPD activity (>50 pmol/min/mg protein, F ranging between 1.7 and 5. 2), whereas 776C did not modify FU cytotoxicity in the remaining cell lines expressing the lowest DPD activity (<50 pmol/min/mg protein, F ranging between 0.7 and 1.4). F was significantly different between these two groups of cell lines (P = 0.005). These results point out that DPD is an interesting target for FU pharmacomodulation.

Antimetabolites, Antineoplastic↗
PubMed1994

Inhibition of dihydropyrimidine dehydrogenase by alpha-interferon: experimental data on human tumor cell lines.

Interferons (IFNs) are very promising fluorouracil (FU) biochemical modulators. The pharmacological origin sustaining the FU-IFN synergistic interaction is not clearly understood. It was recently shown that alpha-IFN was associated with a dose-dependent decrease in FU clearance in treated patients. Dihydropyrimidine dehydrogenase (DPD) is the key regulating enzyme for FU catabolism. The effects on DPD exerted by both the IFN dose and the duration of exposure were evaluated in a panel of five human cancer cell lines. All cell lines investigated exhibited quantifiable DPD activity with inter-cell-line variability (0.118-0.318 nmol min-1 mg protein-1). A prolonged exposure to IFN (up to 5 days) was necessary to obtain a significant inhibition of DPD activity. A concentration-dependent significant decrease in DPD activity, reaching 50% of the initial activity determined for the highest IFN concentration (10(5) IU/ml), was demonstrated in all cell lines tested (5-day IFN exposure). For three cell lines, IFN potentiated the FU-induced growth inhibition in a concentration-dependent manner. Considering all cell lines and all IFN concentrations, it appears that globally, the greater the inhibition of DPD activity, the greater the FU potentiation (Spearman rank correlation on all cell lines, P = 0.011).

Carcinoma↗
PubMed1994

A role for dihydropyrimidine dehydrogenase and thymidylate synthase in tumour sensitivity to fluorouracil.

Despite being one of the oldest anti-cancer drugs, fluorouracil (FU) is still being increasingly used in cancer chemotherapy. The source of variability for FU sensitivity in patients may be complex, although an overproduction of thymidylate synthase (TS) was the only mechanism of resistance identified in tumours from FU-resistant patients. Dihydropyrimidine dehydrogenase (DPD) is the first and rate-limiting enzyme of FU catabolism. Thus, DPD activity may be a potential factor for controlling FU responsiveness. A panel of 19 human tumour cell lines, including digestive tract, breast and head and neck cancer cells, were investigated. Both TS and DPD activities were measured in parallel to FU responsiveness. None of the cell lines had been previously exposed to FU, and thus expressed a spontaneous sensitivity to FU. Sensitivity between cell lines showed marked differences, with IC50 values ranging from 45 ng/ml (colon cell line) to 5063 ng/ml (head and neck cell line). TS activity was measurable in all cell lines and varied within a 46-fold range. DPD activity was detected in all but four cell lines, showing a 100-fold range of variation. Cell lines most sensitive to FU exhibited the lowest DPD and TS activities and vice versa. Simple linear regression analysis showed that both TS (r2 = 0.22, P = 0.042) and DPD (r2 = 0.27, P = 0.022) activities were significantly correlated to FU effectiveness (log 10 IC50): the greater the enzyme activities, the higher the FU IC50. TS and DPD were demonstrated to be independent variables. A multiple regression analysis showed that the combination of TS and DPD activities explained 36% of the variability in FU IC50 (r2 = 0.36, P = 0.01). Two groups of cell lines could be identified, one group with both low TS and low DPD activities (G1), and the other with either high TS and/or high DPD activities (G2). Mean FU IC50 values were 193 and 930 ng/ml in G1 and G2, respectively, and this difference in FU sensitivity was highly significant (P = 0.009). The present study shows, for the first time, that DPD activity in tumour cells is an independent factor significantly related to FU sensitivity. These results should encourage DPD and TS coupled measurements in tumours of patients before FU treatment in order to establish their prognostic relevance. DPD and TS measurements could also be used during the treatment course to determine the implication of these enzymes in the development of tumour resistance to FU.

Breast Neoplasms↗
PubMed1994

Cytotoxic effects of long-term circulating ultrafiltrable platinum species and limited efficacy of haemodialysis in clearing them.

We applied haemodialysis to clear platinum (Pt) circulating species following renal insufficiency due to an accidental cisplatin overdosage (205 mg/m2 instead of 100 mg/m2). Serum samples were repeatedly obtained during this clinical episode from day 5 up to day 30 after cisplatin dosing. A serum aliquot taken at day 22 after cisplatin administration was tested to assess the possible cytotoxicity exhibited by the circulating Pt species on a head and neck tumour cell line. The profile of ultrafiltrable (UF) Pt during successive haemodialysis cycles was striking. After each haemodialysis cycle, a marked decrease in UF Pt, occurred but was followed by more or less pronounced rebounds. Cisplatin concentration-cytotoxic effect curves obtained in vitro from patient serum before cisplatin administration and healthy control serum exhibited very similar concentration effect profiles. In contrast, the patient serum taken at day 22 after cisplatin administration resulted in marked cytotoxic effects, which were much greater than those which could have been anticipated considering the Pt concentration of this serum sample. The present report underlines the limited usefulness of haemodialysis for rescuing cisplatin treated patients, exhibiting unanticipated postinfusion renal failure with overexposure to the drug. The in vitro investigations suggest that pharmacological effects of Pt derivatives may not only be attributable to short-term effects of the drug diffusion into tissues, but also to more delayed effects from Pt circulating species.

Adenocarcinoma↗
PubMed1994

Determination of oestrogen receptors by enzyme immunoassay. Technical differences between laboratories and their consequences.

When multicentre breast cancer trials are performed, receptor analyses must be comparable both over time and in the participating laboratories. However, we show for the first time a high variability for the distribution of oestradiol receptor (ER) values measured by enzyme immunoassay (EIA) from 1987 to 1991. This variability could be explained by calibration changes in the immunoassay kits. We have also analysed the influence on ER-EIA levels of technical differences between laboratories apart from the assay itself. Many steps emerged as being critical, i.e. homogenisation buffer, homogenisation procedure and cytosol dilution. Finally, we show that addition of 4-monohydroxytamoxifen increases the apparent ER content measured by EIA in 92% of cytosols. Thus, many factors must be controlled to ensure high precision with ER-EIA assays. We have to be particularly cautious with the conformational changes that could occur during cytosol preparation and that could also pre-exist in the tumour samples. Quality controls of cytosol preparation are essential.

Breast Neoplasms↗