Prediction of chemotherapeutic response by Technetium 99m--MIBI scintigraphy in breast carcinoma patients

Role of 99mTc-sestamibi Scintimammography in Predicting Response to Neoadjuvant Chemotherapy in Locally Advanced Breast Cancer: A Prospective Study

Background

Neoadjuvant chemotherapy (NACT) is the first line of management for locally advanced breast cancer (LABC). However, chemoresistance is prevalent in 18%-50% of the cases. One of the important and most studied causes of chemoresistance is P-glycoprotein (Pgp) expression. 99mTc-sestamibi scintimammography may serve as a useful imaging tool to predict Pgp expression, thereby response to NACT.

Aim

The aim was to study the role of 99mTc-sestamibi scintimammography in predicting response to NACT in treatment-naive, biopsy-proven LABC patients.

Materials and Methods

99mTc-sestamibi scintimammography (early and delayed images) was performed on a total of 34 patients. Eight patients were lost to follow-up, and only 26 (25 females and 1 male) patients were available for final analysis, with a mean age of 49.7 ± 10.7 years. 99mTc-sestamibi washout rate (WOR) (%) and T/B buildup were calculated. Pre-NACT and Post-NACT tumor sizes were measured clinically, and a % decrease in tumor size was calculated. The WOR and T/B buildup values were correlated with the % decrease in tumor size.

Results

We found a statistically significant negative correlation between WOR (%) and % decrease in tumor size and a statistically significant positive correlation between T/B buildup and % decrease in tumor size. Furthermore, we found a positive correlation between the early T/B ratio and the Ki-67 index (P = 0.22).

Conclusion

Early categorization of responders and nonresponders can help in optimal therapy planning. 99mTc-sestamibi scintimammography can serve as an imaging marker for Pgp expression, thereby predicting clinical response to NACT in LABC patients. Further studies with larger sample sizes are warranted to consolidate the above findings.

In vivo characterization of [18F]AVT-011 as a radiotracer for PET imaging of multidrug resistance

Purpose

Multidrug resistance (MDR) impedes cancer treatment. Two efflux transporters from the ATP-binding cassette (ABC) family, ABCB1 and ABCG2, may contribute to MDR by restricting the entry of therapeutic drugs into tumor cells. Although a higher expression of these transporters has been correlated with an unfavorable response to chemotherapy, transporter expression does not necessarily correlate with function. In this study, we characterized the pharmacological properties of [¹⁸F]AVT-011, a new PET radiotracer for imaging transporter-mediated MDR in tumors.

Methods

AVT-011 was radiolabeled with ¹⁸F and evaluated with PET imaging in preclinical models. Transport of [¹⁸F]AVT-011 by ABCB1 and/or ABCG2 was assessed by measuring its uptake in the brains of wild-type, Abcb1a/b^−/−, and Abcg2^−/− mice at baseline and after administration of the ABCB1 inhibitor tariquidar (n = 5/group). Metabolism and biodistribution of [¹⁸F]AVT-011 were also measured. To measure ABCB1 function in tumors, we performed PET experiments using both [¹⁸F]AVT-011 and [¹⁸F]FDG in mice bearing orthotopic breast tumors (n = 7–10/group) expressing clinically relevant levels of ABCB1.

Results

At baseline, brain uptake was highest in Abcb1a/b^−/− mice. After tariquidar administration, brain uptake increased 3-fold and 8-fold in wild-type and Abcg2^−/− mice, respectively, but did not increase further in Abcb1a/b^−/− mice. At 30 min after injection, the radiotracer was > 90% in its parent form and had highest uptake in organs of the hepatobiliary system. Compared with that in drug-sensitive tumors, uptake of [¹⁸F]AVT-011 was 32% lower in doxorubicin-resistant tumors with highest ABCB1 expression and increased by 40% with tariquidar administration. Tumor uptake of [¹⁸F]FDG did not significantly differ among groups.

Conclusion

[¹⁸F]AVT-011 is a dual ABCB1/ABCG2 substrate radiotracer that can quantify transporter function at the blood-brain barrier and in ABCB1-expressing tumors, making it potentially suitable for clinical imaging of ABCB1-mediated MDR in tumors.

Electronic supplementary material

The online version of this article (10.1007/s00259-019-04589-w) contains supplementary material, which is available to authorized users.

Effect of trifluoperazine on Tc-99m sestamibi uptake in patients with advanced nonsmall cell lung cancer

OBJECTIVE

The aim of this study was to investigate whether there is an effect of trifluoperazine on Tc-99m  methoxyisobutylisonitrile (MIBI) uptake in patients with advanced nonsmall cell lung cancer (NCLC).

MATERIALS AND METHODS

A total of 23 patients with biopsy-proven advanced NCLC who had no previous history of chemo-radiotherapy, underwent baseline dual phase planar, single photon emission computed tomography and whole body Tc-99m MIBI scintigraphy performed at 20 and 120 min. After oral administration of trifluoperazine (5 mg, 2 times a day, for 5 days), dual phase Tc-99m MIBI scintigraphy was repeated. For each patient, and for both studies, regions of interest were drawn over the tumor area (T) and over the normal lung area (L) on the contralateral side in transverse slices where tumor was visualized clearly. Then, early and delayed T/L ratios and washout rate (WR) were calculated.

RESULTS

Tc-99m MIBI was accumulated in the cancer tissue in all of the patients. Delayed ratio after the oral administration of trifluoperazine (DR2) was significantly higher (P = 0.039) than delayed ratio before trifluoperazine (DR1). We found no significant differences of early ratio before trifluoperazine (ER1) and early ratio after trifluoperazine (ER2), and washout rate before (WR1) and washout rate after trifluoperazine (WR2).

CONCLUSION

In patients with advanced NCLC, trifluoperazine treatment in addition to chemotherapy might be useful. However, our results need to be confirmed in larger series of patients.

Functional imaging of multidrug resistance in breast cancer

Intrinsic or acquired multidrug resistance is the major cause of treatment failure in many human cancers. Multiple cellular mechanisms may contribute to the development of multidrug resistance including overexpression of P-glycoprotein (Pgp). The use of 99mTc-labeled lipophilic cations, which are transport substrate of Pgp, raised the possibility to predict the tumor response to treatment and to identify patients who will become refractory to subsequent therapy. Among these agents, 99mTc-MIBI is the most widely evaluated tracer and may serve as a paradigm of this class of compounds. In particular, many studies have shown the prognostic value of 99mTc-MIBI scan in different types of malignancy including breast cancer and the correlation with the expression of Pgp. However, additional mechanisms of cell resistance, mainly involving alterations of apoptosis, may also affect 99mTc-MIBI uptake in tumors. In particular, overexpression of the anti-apoptotic protein Bcl-2 prevents tumor cells to enter apoptosis and inhibits tracer accumulation into mitochondria. Therefore, while an absent or reduced early tracer uptake in large breast carcinomas reflects the existence of a defective apoptotic program, an enhanced tracer clearance in 99mTc-MIBI positive lesions reflects the activity of drug transporters such as Pgp. The existence of two different mechanisms underlying the predictive role of 99mTc-MIBI scan may be important to establish whether individual patients may benefit from Pgp inhibitors or Bcl-2 antagonists.

Role of Tc99m-Sestamibi scintimammography in assessing response to neoadjuvant chemotherapy in patients with locally advanced breast cancer

INTRODUCTION

Neoadjuvant chemotherapy (NACT) is an essential part of multi-disciplinary management of locally advanced breast cancer (LABC). In this study, we aimed at evaluating the role of Tc99m-Sestamibi scinti-mammography in assessing response to NACT in patients with LABC.

MATERIALS AND METHODS

A total of 42 patients of histologically proven LABC were enrolled in this prospective study. Imaging was performed according to pre-defined protocol at 10 min and 4 h after injection of tracer before the start of chemotherapy, 48 h after start of chemotherapy and at the end of chemotherapy. Quantitative parameters were obtained by calculating the ratio of activity in a region of interest (ROI) drawn over the tumor and the same sized ROI drawn in corresponding location in contra lateral breast.

RESULTS

At the end of chemotherapy, 6 patients achieved complete response, 25 achieved partial response, 11 had stable disease. Various retention indices calculated at baseline, 48 h after first cycle of NACT, and at the end of chemotherapy showed statistically significant difference in responders and non-responders. By using 84.05 as cut-off point for retention index (RI) of tumor calculated 48 h after first cycle of NACT (RI 2) the positive predictive value and negative predictive value, were found to be 41.9% and 72.7% respectively in differentiating responders from non-responders.

CONCLUSION

Early response assessment in patients with LABC to NACT with Tc99m-Sestamibi scintimammography is feasible and if confirmed by further studies can find routine clinical application in differentiating responders from non-responders.

Protein profile study of breast-tissue homogenates by HPLC-LIF

Proteomics is a promising approach for molecular understanding of neoplastic processes including response to treatment. Widely used 2D-gel electrophoresis/Liquid chromatography coupled with mass spectrometry (LC-MS) are time consuming and not cost effective. We have developed a high-sensitivity (femto/subfemtomoles of protein/20 mul) High Performance Liquid Chromatography-Laser Induced Fluorescence HPLC-LIF instrument for studying protein profiles of biological samples. In this study, we have explored the feasibility of classifying breast tissues by multivariate analysis of chromatographic data. We have analyzed 13 normal, 17 malignant, 5 benign and 4 post-treatment breast-tissue homogenates. Data was analyzed by Principal Component Analysis PCA in both unsupervised and supervised modes on derivative and baseline-corrected chromatograms. Our findings suggest that PCA of derivative chromatograms gives better classification. Thus, the HPLC-LIF instrument is not only suitable for generation of chromatographic data using femto/subfemto moles of proteins but the data can also be used for objective diagnosis via multivariate analysis. Prospectively, identified fractions can be collected and analyzed by biochemical and/or MS methods.

(99m)Tc-MIBI imaging for prediction of therapeutic effects of second-generation MDR1 inhibitors in malignant brain tumors

The aim of this study was to explore whether (99m)Tc-methoxyisobutylisonitrile ((99m)Tc-MIBI) is suitable to elucidate multidrug resistance and prediction of potentiation of antitumor agents by second-generation MDR1 inhibitors (PSC833, MS-209) in malignant brain tumors in rat. Malignant tumor cells (RG2 and C6 gliomas, Walker 256 carcinoma) were incubated with low dose vincristine (VCR) to induce multidrug resistance. MTT assay demonstrated a significant increase of surviving fractions in VCR-resistant sublines compared to those of drug-naive cells. Reverse transcriptase polymerase chain reaction revealed higher expression of MDR1 mRNA in VCR-resistant cells than drug-naive cells in each line. Volume distribution (V(d)) of (99m)Tc-MIBI was negatively correlated with MDR1 mRNA expression among drug-naive and VCR-resistant cells. MDR1 inhibitors decreased surviving fractions and increased V(d) of (99m)Tc-MIBI significantly in VCR-resistant sublines, whereas MDR1 mRNA expression was unchanged. These findings indicate that (99m)Tc-MIBI efflux was functionally suppressed by MDR1 inhibitors. Autoradiographic images of (99m)Tc-MIBI revealed higher uptake in drug-naive cells at basal ganglia compared with VCR-resistant cells at the opposite basal ganglia of rats. Oral administration of the second-generation MDR1 inhibitors significantly increased (99m)Tc-MIBI accumulation of both tumors. Therapeutic effects of VCR with or without the MDR1 inhibitors were also evaluated autoradiographically using (14)C-methyl-L-methionine ((14)C-Met) and MIB-5 index. (14)C-Met uptake and MIB-5 index of both tumors treated with VCR following the MDR1 inhibitor treatment significantly decreased compared with tumors treated with VCR alone. Analysis of (99m)Tc-MIBI accumulation is considered informative for detecting MDR1-mediated drug resistance and for monitoring the therapeutic effects of MDR1 inhibitors in malignant brain tumors.

Neoadjuvant therapy in locally advanced breast cancer: 99mTc-MIBI mammoscintigraphy is not a reliable technique to predict therapy response

Mammoscintigraphy (MMS) has been indicated as a useful tool in predicting response to therapy in cancer. However, contrasting results have been reported in the literature for breast cancer patients. The aim of this study was to explore the role of MMS in locally advanced breast cancer (LABC) patients. Fifty-one patients affected by LABC and scheduled for neoadjuvant therapy were enrolled. Breast tumor status was evaluated at baseline, during therapy and at the completion of therapy by radiological techniques and by MMS. Pre-therapy (MMS1) and post-therapy MIBI (2-methoxyisobutilysonitrile) images (MMS2-3) were analyzed. MMS1 was performed in all pts, 41 carried out MMS2 and 27 had MMS3. Tumor uptake and washout in MMS1 did not show any correlation with the therapy response. The absence of any association between tumor uptake and washout with respect to therapy response suggests that MMS is not a reliable technique to predict therapy response in LABC.

Usefulness of Scintimammography With Tc-99m MIBI in Clinical Practice

Radiographic mammography (MM) is routinely used to diagnose breast cancer. MM has a number of well-known limitations, especially in cases of a dense or dysplastic breast. Scintimammography (SM) with Tc-99m MIBI has been successfully used as a useful complement to MM. The authors report a case of a 57-year-old woman with MM with tiny calcifications in the left breast, which were classified by the radiologist as probably benign lesions. SM with Tc-99m MIBI showed a focal area of increased uptake in the upper outer quadrant of the left breast. On the basis of SM results, an excisional biopsy was performed and pathologic examination revealed infiltrating ductal carcinoma.

Multidrug Resistance/P-Glycoprotein and Breast Cancer: Review and Meta-Analysis

Previously untreated breast cancer is relatively sensitive to a range of anticancer drugs. However, exposure to these drugs is often followed by acquisition of multidrug resistance, which is associated with a significantly worse outcome. One of the more widely studied mechanisms of drug resistance is the function of P-glycoprotein (P-gp), a membrane transporter with a wide range of substrates, including several anticancer agents, and a member of the ATP-binding cassette superfamily of proteins. A review of the published literature indicates that P-gp expression is detected in a significant percentage of breast cancers. Moreover, P-gp expression is increased after exposure to chemotherapeutic drugs (particularly those known to be P-gp substrates), and correlates with a worse response to treatment, especially when detected following treatment, in both the adjuvant and neoadjuvant settings. Consequently, P-gp represents a potential biomarker of drug resistance. However, a direct role of P-gp as a cause of clinical drug resistance has not been adequately tested in breast cancer. Future studies aimed at validating the mechanistic role of P-gp should include trials of multidrug resistance reversal using P-gp-specific inhibitors and relating results to the levels of P-gp expression. Future studies should also take into account the potentially multifactorial nature of multidrug resistance.

Monitoring the response of large (>3 cm) and locally advanced (T3-4, N0-2) breast cancer to neoadjuvant chemotherapy using (99m)Tc-Sestamibi uptake

BACKGROUND AND AIM

(99m)Tc-Sestamibi (MIBI) scintimammography has an established role in the diagnosis of breast cancer. As a functional imaging technique, it may also be useful in assessing the response to chemotherapy. The aim of this study was to assess the effectiveness of the technique for this purpose.

METHODS

Twenty-six patients undergoing neoadjuvant chemotherapy for large or locally advanced breast cancer were monitored using the tumour to background ratio measured on MIBI scintimammograms. Patients were assessed and the size of the tumour was measured by callipers and ultrasonography before and at the end of treatment. Patients were assessed as complete, partial or non-responders. Following chemotherapy, patients proceeded to surgery with pathological evaluation of the operative specimen.

RESULTS

Twenty-four of the 26 patients showed a reduction in MIBI uptake on completion of chemotherapy. Residual tumour was demonstrated on the scintimammogram in four patients and all had significant residual disease on histology. In the remaining 22 patients, the final scintimammogram was negative, although three patients were assessed as non-responders and had large residual tumours on histology.

CONCLUSION

A positive MIBI scan is highly predictive of the presence of significant residual disease on completion of chemotherapy. However, a negative MIBI scan does not rule out the presence of considerable residual tumour. Whereas ultrasound and clinical assessment may underestimate the response to chemotherapy, MIBI imaging tends to overestimate the response.

Prediction of response to docetaxel by immunohistochemical analysis of CYP3A4 expression in human breast cancers

BACKGROUND

Docetaxel (DOC) is inactivated by CYP3A4, high expression of which in tumor tissue might serve as a resistance mechanism. In the present study, the CYP3A4 protein level in breast cancers was determined by immunohistochemistry, and its relationship with the response to DOC treatment was studied.

MATERIALS AND METHODS

Thirty-one patients with locally advanced (n = 21) or recurrent (n = 10) breast cancers underwent tumor biopsy, followed by DOC treatment (60 mg/m2 q3w). Expression of CYP3A4 was studied by immunohistochemistry.

RESULTS

Patients with CYP3A4 negative tumors (n = 15) by immunohistochemistry showed a significantly (P < 0.01) higher response rate (67%) to DOC treatment than those with CYP3A4 positive tumors (n = 16, 19%). The positive predictive value, negative predictive value, and diagnostic accuracy of CYP3A4 expression by immunohistochemistry in the prediction of response to DOC were 67%, 81%, and 74%, respectively.

CONCLUSION

Immunohistochemical analysis of CYP3A4 expression in tumor cells might be clinically useful in the prediction of tumor response to DOC.

Imaging recognition of multidrug resistance in human breast tumors using 99mTc-labeled monocationic agents and a high-resolution stationary SPECT system

Imaging recognition of multidrug-resistance by 99mTc-labeled sestamibi, tetrofosmin and furifosmin in mice bearing human breast tumors was evaluated using a high-resolution SPECT, FASTSPECT. Imaging results showed that the washout rates in drug-resistant MCF7/D40 tumors were significantly greater than that in drug-sensitive MCF7/S tumors. Furifosmin exhibited greater washout from both MCF7/S and MCF7/D40 than sestamibi, while tetrofosmin washout was greater than sestamibi in MCF7/D40 only. Feasibility of the monocationic agents for characterizing MDR expression was well clarified with FASTSPECT imaging.

Monitoring neoadjuvant chemotherapy in breast cancer using quantitative diffuse optical spectroscopy: a case study

Presurgical chemotherapy is widely used in the treatment of locally advanced breast cancer. Monitoring the response to therapy can improve survival and reduce morbidity. We employ a noninvasive, near-infrared method based on diffuse optical spectroscopy (DOS) to quantitatively monitor tumor response to neoadjuvant chemotherapy. DOS was used to monitor tumor response in one patient with locally advanced breast cancer throughout the course of her therapy. Measurements were performed prior to doxorubicin-cyclophosphamide therapy and at several time points over the course of three treatment cycles (68 days). Our results show strong tumor to normal (T/N) tissue contrast in total hemoglobin concentration (T/N=2.4), water fraction (T/N=6.9), tissue hemoglobin oxygen saturation, S(t)O(2) (T/N=0.9), and lipid fraction (T/N=0.7) prior to treatment. Over a 10-week period, the peak total hemoglobin and water dropped 56 and 67%, respectively. Lipid content nearly returned to baseline (T/N =0.9) while S(t)O(2) exceeded pretreatment levels (T/N =1.5). Approximately half of the hemoglobin and water changes occurred within 5 days of treatment (26 and 37%, respectively). These data suggest that noninvasive, quantitative optical methods that characterize tumor physiology may be useful in assessing and optimizing individual response to neoadjuvant chemotherapy.

Inhibition of early 99mTc-MIBI uptake by Bcl-2 anti-apoptotic protein overexpression in untreated breast carcinoma

Lack of technetium-99m methoxyisobutylisonitrile ((99m)Tc-MIBI) uptake is consistently reported to predict poor response to subsequent chemotherapy in a variety of human malignant tumours. Since (99m)Tc-MIBI accumulates within mitochondria, which also play a central role in apoptosis through the integration of death signals by Bcl-2 family members, we tested whether early (99m)Tc-MIBI uptake is affected by alterations of the apoptotic pathway. Forty-two breast cancer patients were intravenously injected with 740 MBq of (99m)Tc-MIBI and planar images were obtained 10 min post injection with the patients in the prone lateral position. Ten carcinomas failed to accumulate (99m)Tc-MIBI and could not be visualised on scintigraphic images despite being larger than 1.8 cm (MIBI negative). Thirty-two of the 42 breast carcinomas showed focal uptake of (99m)Tc-MIBI (MIBI positive), and 10 min tumour-to-background ratios (T/B) varied between 1.14 and 6.93. The apoptotic index, the rate of proliferation, and the expression of the anti-apoptotic Bcl-2 protein and pro-apoptotic Bax protein were assessed in surgically excised tumours. All MIBI-negative carcinomas showed a dramatic and statistically significant reduction in the apoptotic index as compared with MIBI-positive lesions (mean+/-SD, 0.14+/-0.15 vs 1.28+/-0.83, P<0.0001) independently of rate of proliferation, tumour size and P-glycoprotein expression. Significantly higher levels of Bcl-2 were also found in MIBI-negative as compared with MIBI-positive carcinomas. In MIBI-positive lesions, an inverse significant correlation was found between T/B ratios and Bcl-2 levels ( r=-0.50, P<0.01). Our findings indicate that early uptake of (99m)Tc-MIBI in breast carcinomas is affected by alterations of apoptotic pathway. High levels of Bcl-2, despite the stabilisation of mitochondrial membrane potentials, prevent accumulation of (99m)Tc-MIBI in tumour cells. In conclusion, absent or reduced early (99m)Tc-MIBI uptake in large tumours may indicate a Bcl-2-mediated resistance to chemo- and radiotherapy.

Early response to chemotherapy: a surrogate for final outcome of Hodgkin's disease patients that should influence initial treatment length and intensity?

BACKGROUND

Early adjustment of treatment may benefit the patient. In order to guide treatment adjustment, use of early response (ER) or early complete response (ECR), judged after the few initial cycles of chemotherapy, is common in pediatric and also adult Hodgkin's and non-Hodgkin's studies. Paradoxically, almost no data support this strategy.

PATIENTS AND METHODS

The influence of ECR on outcome was evaluated in three series of advanced Hodgkin's disease (HD), leading to a series of questions.

RESULTS

The 1982 EORTC study assessed prospectively the time frame needed to reach an apparent complete response (CR) through repeated tumor measurements. In patients assessed at mid-treatment before the fifth cycle, both 15 year freedom from progression (FFP) and overall survival (OS) were superior in ECR patients compared with other patients continued on the same treatment (61% versus 37%; P < 0.001). A series of questions arise from these observations. Question 1: is the shortening of treatment detrimental? In a randomized Swedish trial, in one arm treatment was shortened in patients evaluated from the fifth cycle as ECR as compared with the standard eight cycles arm, 10 year cause-specific-survival (CSS) was 53 versus 69% [not significant (ns)]; 10 year OS 49% versus 58% (ns). Conversely, in the EORTC 20884 study, ECR patients given only six cycles did as well as patients entering CR later and, for this reason, given eight cycles (identical 6 year event-free survival 75%). Question 2: is early treatment adaptation in patients who failed to reach ER beneficial? In the French MDH 90 trial, 15% of children failed to reach ECR after four cycles; in these children only, anthracyclines plus alkylating agents were given and the dose of radiotherapy increased, improving the results observed in the previous trial. In the EORTC 20884 study, patients who failed to reach an ECR were switched earlier to involved field RT: their results matched those of ECR patients, at the difference of the previous trial. Question 3: is ER a predicting factor that can be used with any type of treatment? Probably not, based on the German Hodgkin's Lymphoma Study Group trial HD 9: ECR is highly dependent on specific interval from treatment start and on treatment intensity.

DISCUSSION

More general questions stem from these results. Question 4: is the definition of ER secured? With conventional imaging, the different methods for response assessment at end treatment also lead to different response rates; the assessment in the middle of treatment itself and the use of newer imaging techniques may further increase the variation. Indeed, question 5 is: is ER a concept based on any biology? Correlation to markers, 99mTc uptake, PET and hematological tolerance might help to pinpoint how and why ER represents a surrogate for final outcome.

CONCLUSION

ER is a surrogate for final outcome, reflecting both tumor burden and activity. This predictability may, and possibly should, impact on treatment.

Predictive value of (99m)Tc sestamibi scintigraphy in the evaluation of doxorubicin based chemotherapy response in patients with advanced breast cancer

Resistance to doxorubicin based chemotherapy is a major therapeutic problem limiting advanced breast cancer treatment. 99mTc hexakis-2-methoxyisobutylisonitrile ((99m)Tc-MIBI) has been reported to be extruded from tumour cells by the P-glycoprotein and multidrug resistance protein encoded by MDR1 and MRP1 genes, respectively. These proteins are involved in the cellular efflux of several chemotherapeutic agents including doxorubicin. The aim of this study was to investigate the clinical value of a standard (99m)Tc-MIBI scintimammography technique in the prediction of response to chemotherapy in advanced breast cancer patients. Fifty-six lesions from 33 female patients with locally advanced (n=27) or recurrent breast cancer (n=6) were included in the study. MIBI scintigraphy was performed 2-8 days prior to chemotherapy (FAC regimen). Images were acquired 10 min and 1 h post-injection of 740-1110 MBq of (99m)Tc-MIBI. Tumour-to-normal background tissue uptake ratios were calculated on each lesion in the early (T/B(e)) and delayed phase of the study (T/B(d)). Both T/B(e) and T/B(d) ratios were significantly higher (P<0.0001) in responders (n=43) than nonresponders (n=13). Diagnostic values of (99m)Tc-MIBI in the prediction of chemotherapy response were evaluated using the arbitrary cut-off values of 1.5 for T/B(e) and 1.4 forT/B(d). Sensitivity, specificity, positive and negative predictive values were 88.4%, 92.3%, 97.4%, 70.6%; and 90.7%, 100.0%, 100.0%, 76.6%, for T/B(e) and T/B(d), respectively. We conclude that (99m)Tc-MIBI scintigraphy may be a clinically valuable tool for guiding chemotherapy in advanced breast cancer patients.

Integrins and extracellular matrix: a novel mechanism of multidrug resistance

Multidrug resistance remains the major hurdle to successful cancer treatment. Classical mechanisms of multidrug resistance include drug efflux pumps, glutathione-S-transferase upregulation and topoisomerase II-associated multidrug resistance. However, despite extensive research, the clinical relevance of these mechanisms remains unclear and no significant clinical benefit has materialized. Recently, a novel mechanism of multidrug resistance has been identified--extracellular matrix-mediated multidrug resistance: integrin-mediated adherence of cells to extracellular matrix proteins results in significant resistance to many anticancer agents that induce cell death via unrelated mechanisms. Verification of the mechanisms of action of this novel phenomenon will hopefully identify new therapeutic targets to aid in the fight against cancer.

Monitoring therapy in breast cancer

Breast cancer remains one of the most common cancers in the developed world. New treatments are proving effective against both limited disease and metastases. Nuclear medicine is in a unique position as it is one of the only methods used to image the breast which is linked to cell cycle changes, the receptors on the cell surface and the cells' response to chemotherapy. Nuclear medicine is unaffected by the anatomical changes seen post-chemotherapy and radiotherapy and is uniquely placed to become a major methodology in the continued assessment of the breast cancer patient. However, before this can happen the utility of nuclear medicine techniques must be proved in multi-centre trials.