Technetium-99m-sestamethoxyisobutylisonitrile scan as a predictor of chemotherapy response in malignant lymphomas compared with P-glycoprotein expression, multidrug resistance-related protein expression and other prognosis factors

Radiogenomics and Its Role in Lymphoma

PURPOSE OF REVIEW

Imaging features of lymphoma vary regionally. Awareness of site-specific key imaging characteristics of lymphoma can aid in rapid staging and assist in prompt treatment. FDG PET/CT and conventional MRI are readily available diagnostic modalities with excellent sensitivity and good specificity. Diagnostic specificity can be enhanced using emerging PET radiotracers, e.g., FLT and FET.

RECENT FINDINGS

Emerging research has shown higher dimensional analysis (radiomics and radiogenomics) of imaging data can yield information of the underlying genetic aberrations in lymphoma, which can aid in assessing real-time evolution of tumor. CT, PET/CT, MRI, and ultrasound accentuate the intrinsic qualities of lymphoma (e.g., FDG PET/CT for increased metabolic activity, FLT PET/CT for increased proliferation index, and DWI for increased cellularity) and play an essential role in its diagnosis and examination. Advanced radiogenomic analyses use radiomic parameters to deduce genetic variations of lymphoma, providing noninvasive, repeatable, and real-time surveillance of its genetic progression.

Predicting tumour response

Response prediction is an important emerging concept in oncologic imaging, with tailored, individualized treatment regimens increasingly becoming the standard of care. This review aims to define tumour response and illustrate the ways in which imaging techniques can demonstrate tumour biological characteristics that provide information on the likely benefit to be received by treatment. Two imaging approaches are described: identification of therapeutic targets and depiction of the treatment-resistant phenotype. The former approach is exemplified by the use of radionuclide imaging to confirm target expression before radionuclide therapy but with angiogenesis imaging and imaging correlates for genetic response predictors also demonstrating potential utility. Techniques to assess the treatment-resistant phenotype include demonstration of hypoperfusion with dynamic contrast-enhanced computed tomography and magnetic resonance imaging (MRI), depiction of necrosis with diffusion-weighted MRI, imaging of hypoxia and tumour adaption to hypoxia, and 99mTc-MIBI imaging of P-glycoprotein mediated drug resistance. To date, introduction of these techniques into clinical practice has often been constrained by inadequate cross-validation of predictive criteria and lack of verification against appropriate response end points such as survival. With further refinement, imaging predictors of response could play an important role in oncology, contributing to individualization of therapy based on the specific tumour phenotype. This ability to predict tumour response will have implications for improving efficacy of treatment, cost-effectiveness and omission of futile therapy.

99mTechnetium-SESTAMIBI Uptake in Malignant Lymphomas. Correlation with Chemotherapy Response

BACKGROUND

The rationale of the present study is based on the property of technetium-SESTAMIBI to enter malignant and other highly metabolic cells, and then to be pumped out of them by the multidrug-resistant (MDR) system, strongly depending on the expression of the MDR-1 gene encoded P-glycoprotein (Pgp-170).

METHODS AND RESULTS

Forty-one patients with malignant lymphoma were studied before chemotherapy. Images were taken 30 min (early) and 180 min (late) after intravenous injection of (99m)Tc-MIBI, and then visually interpreted. They were correlated with clinical response defined as chemosensitive (ChS) when a >6 month remission was attained, and chemoresistant (ChR) to any other response. Of 41 patients, 27 had an early positive uptake, 18 (67%) were ChS, and 9 (33%) ChR. Of these 27 patients, 19 also had late positive scans; 15 (79%) were ChS, and only 4 were ChR (p = 0.037). Conversely, 10 of 14 remaining patients with negative early scans were ChR. Eight patients had an early positive study; however, the late retention of (99m)Tc-MIBI was negative and the relationship to chemotherapy response was not conclusive. A breakdown of data was made according to histology. Patients with low grade lymphoma had the strongest correlation between (99m)Tc-MIBI uptake and chemosensitivity. Patients with high grade lymphoma had only a trend, and patients with Hodgkin's disease had an indefinable correlation.

CONCLUSIONS

This study takes advantage of the relationship between the ability to uptake and retain (99m)Tc-MIBI, a Pgp-170 substrate, by lymphomatous tumors. This attribute, combined with other clinical data, could help to select tailored treatments for patients that are likely to be chemoresistant before treatment.

Expression of permeability-glycoprotein (P-gp) and uptake of technetium-99m-hexakis-2-methoxy-isobutyl-isonitrile (99Tcm-MIBI) in malignant tumour of the head and neck

OBJECTIVES

The purpose of this study is to estimate the role of permeability-glycoprotein (P-gp) in the technetium-99m-hexakis-2-methoxy-isobutyl-isonitrile (99Tc(m)-MIBI) scintigraphy.

METHODS

71 patients with squamous cell carcinoma (39 patients with well differentiated, 19 with moderately differentiated and 13 with poorly differentiated tumour) were examined. Eighteen of these patients underwent 99Tc(m)-MIBI scintigraphy (early and delayed scans). The tumour retention index, obtained from the ratio of the accumulation of the delayed scan to that of the early scan, was divided into three groups. The immunohistochemical evaluation of P-gp expression was performed in all 71 patients. Levels of the P-gp expression were classified into three grades (score 0, 1 and 2). Correlations among the tumour retention index, the P-gp expression and the tumour tissue differentiation were evaluated.

RESULTS

17 of 18 patients showed a decreasing of the tumour retention index ranging from 0.70 to 0.93 (mean+/-SD=0.850+/-0.071). The tumour retention index showed a statistical correlation with the P-gp expression and the tumour tissue differentiation (chi-squared=7.802>7.779, P=0.10 and 16.835>14.860, P=0.005, respectively). Moreover, there was a statistical correlation between the P-gp expression and the tumour tissue differentiation (chi-squared=14.863>14.860, P=0.005).

CONCLUSION

There is a possibility that the P-gp expression is high in the high-grade malignant tumours and P-gp causes the decrease of tumour retention index.

To use MIBI or not to use MIBI? That is the question when assessing tumour cells

99mTc-sestamibi (MIBI) is a well-known tumour imaging agent. Its retention within tumour cell mitochondria is related to perfusion and to the magnitude of the electrical gradient, reflecting cell viability. Several internal cell factors modulate this uptake; for example, multidrug resistance membrane proteins (Pgp and MRP1) and anti-apoptotic BCl-2 protein of the outer mitochondrial membrane can limit retention of MIBI. At the early stage of cell apoptosis, the electrical driving forces of MIBI uptake are impaired, and influx and accumulation are reduced. It seems clear that MIBI can be used before treatment to detect drug resistance, assess anti-apoptotic status and predict treatment efficacy. Although it has been suggested that MIBI might be used to monitor tumour response to treatment, MIBI is unable to differentiate tumours with ongoing apoptosis from those developing drug resistance.

Usefulness of 99mTc-sestamibi scintigraphy in suggesting the therapeutic effect of chemotherapy against gastric cancer

PURPOSE

Imaging with (99m)Tc-sestamibi ((99m)Tc-MIBI) has been used to assess 170-kDa P-glycoprotein (P-gp) expression and predict chemotherapy responses in several types of malignancy, such as breast and lung cancers. The purpose of this study was to evaluate the relationship between (99m)Tc-MIBI accumulation in tumors and sensitivity to chemotherapy in gastric cancer patients.

EXPERIMENTAL DESIGN

Thirty-six patients with advanced gastric cancer underwent (99m)Tc-MIBI scintigraphy before chemotherapy. Patients also underwent endoscopic biopsy, and the expression of P-gp or multidrug resistance-associated protein was analyzed by immunohistochemical staining. The relationship between the accumulation of (99m)Tc-MIBI in tumors and responses to chemotherapy with 5-fluorouracil/cis-diamminedichloroplatinum(II) or epirubicin was examined.

RESULTS

Higher accumulation of (9m)Tc-MIBI in tumors was observed in 25 and 23 of 36 gastric cancer patients at the early (30 min) and delayed (120 min) images, respectively. Accelerated accumulation of (99m)Tc-MIBI negatively correlates with increased expression of P-gp, but not of multidrug resistance-associated protein, as determined by immunohistochemistry in gastric cancer tissues. The response rate to 5-fluorouracil/cis-diamminedichloroplatinum(II) chemotherapy in patients with high (99m)Tc-MIBI accumulation (15.4%) was much lower than that in patients with low (99m)Tc-MIBI accumulation (54.5%). In contrast, patients with high (99m)Tc-MIBI accumulation show a higher response rate (41.7%) to chemotherapy with epirubicin, which is known to be a substrate of P-gp transporter.

CONCLUSIONS

(99m)Tc-MIBI scintigraphy is useful to suggest the responses to chemotherapy of patients with advanced gastric cancer.

Bcl-2 overexpression prevents 99mTc-MIBI uptake in breast cancer cell lines

We have previously shown a correlation between the absence of technetium-99m methoxyisobutylisonitrile ((99m)Tc-MIBI) uptake and overexpression of the anti-apoptotic protein Bcl-2 in human breast carcinoma. To establish a direct cause-effect relationship between Bcl-2 overexpression and reduced (99m)Tc-MIBI uptake, MCF-7 and T47D breast cancer cell lines were stably transfected with the human Bcl-2 gene to increase intracellular protein levels and tested for (99m)Tc-MIBI uptake. All clones overexpressing Bcl-2 showed a dramatic reduction of (99m)Tc-MIBI uptake as compared with mock transfected control cells. Tracer uptake was promptly and partially restored by induction of apoptosis with staurosporine treatment. After 4.5 h of staurosporine treatment, a tenfold increase in (99m)Tc-MIBI uptake was observed in treated as compared with untreated Bcl-2 overexpressing cells. Our findings provide a rational basis for the development of an in vivo test to detect Bcl-2 overexpression in human tumours.

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.