TECHNICAL FIELD

The present invention is directed to a method and system for acquiring spectral data from breast tissue using magnetic resonance spectroscopy (MRS) which can be used to assess risk of breast cancer.

BACKGROUND OF THE INVENTION

Throughout this application various references are cited. They are incorporated by reference herein, to better understand the invention.

There is an important need in the healthcare field to reliably and easily assess a woman’s risk of developing breast cancer. There are various ways that have been proposed for assessing the risk of breast cancer. One way is referred to as an IBIS score.

A recent paper by Gomes at al ¹ linked Methylmalonic acid (MMA) with advancing age and a systemic environment that favours the progression and aggressiveness of tumours. The report suggests that MMA is upregulated in the serum of older people and functions as a mediator of tumour progression. Specifically, it demonstrated that MMA could induce the human transcription factor SOX4 expression and consequently elicit transcriptional reprogramming to give cancer cells aggressive properties. They also hypothesise that MMA may provide a therapeutic target. Methylmalonic acid (MMA or 2-methylpropanedioic acid), CH,CH(CO,H)(CO,H) is a dicarboxylic acid that is a C-methylated derivative of malonate. The MMA derivative is a vital intermediate in the metabolism of fat and protein and Methylmalonic acid metabolism.

While assigning MMA in cerebrospinal fluid in those with Vitamin B12 deficiency, Commodari et al ² demonstrated the pH sensitivity of MMA. At 400MHz the proton MR spectrum has two multiplets centered at 1.23 and 3.17ppm when recorded in D2O at 25C and pH7.2. The multiplets centered at 3.17 ³ has four resonances at 3.14, 3.16, 3.17 and 3.18ppm in the ratio of 1 :4:4: 1. Epidemiological studies report breast density to be an independent risk factor for breast cancer ^4- °. Studies suggest that increased breast density makes a woman 4 to 6-fold more likely to develop breast cancer ⁷ .

A recent study, by others, has shown that high levels of MMA, boost a tumour's malignancy allowing cancer cells to breach new tissues, fight off chemotherapies, and survive.

SUMMARY OF THE INVENTION

In accordance with the present invention, spectral data of woman’s breast tissue has been obtained which enables an assessment of breast cancer depending on the presence of spectral resonances at 3.15 and 3.19 ppm. A tentative assignment of methylmalonic acid, or MMA, has been made for these spectral resonances in the breast tissue of apparently healthy women and those at elevated risk for breast cancer, using in vivo two-dimensional Correlated Spectroscopy (2D COSY) in a 3T clinical scanner. The resonances may be recorded and measured using a full 2D data set, a specific range of delays in the D COSY that encompass the strongest signal for the MMA, or by data mining a ID MR spectrum REF Stairwell Neuroimage. The two resonances which have been recorded at 3.15 and 3.19ppm from women known through other means to have an elevated risk of breast cancer, are consistent with the presence of the MMA molecule in breast tissue. In apparently healthy women, with no significant family history, those with highly dense breast tissue have significantly five times higher levels of MMA than those with low breast density. In those women with an apparently elevated risk of cancer, as judged by their IBIS score, the MMA is highest in those carrying the BRCA gene mutations. The level of the two resonances, recorded at 3.15 and 3.19ppm, increase linearly with the risk of breast cancer as deduced by the IBIS risk score.

While undertaking a study to non-invasively monitor changes at a molecular- level in an apparently healthy breast of those at risk for cancer and those with no known risk for cancer, using in vivo two-dimensional Localised Correlated SpectroscopY (2D COSY), the assignment of MMA was possible. The levels of this molecule in these conditions may be compared with menopausal status and breast density and the IBIS score for risk of cancer. The invention provides a method enabling a determination of the risk of developing breast cancer of a subject, comprising: using a magnetic resonance spectroscopy device to obtain the level of the spectral signal at 3.15 and 3.19 ppm, within the breast tissue of the subject, and comparing the level of the spectral signal obtained with a reference level of a spectral signal at 3.15 and 3.19 ppm from the breast of a healthy subject, to determine whether the level of the signal obtained exceeds the reference level of a healthy subject; is comparable to that of a subject known to be at elevated risk; or is elevated to the level of persons known to be carrying a gene mutation.

The spectral signal at 3.15 and 3.19 ppm may be is that of methylmalonic acid (MM A). The spectral signal may be obtained using 2D COrelated SpectroscopY (2D COSY). The spectral signal may be obtained using data mining of a ID MRS signal. The results may be compared to an International Breast cancer Intervention Study (IBIS) score of the subject.

The invention provides a system for enabling a determination of the risk of developing breast cancer of a subject, comprising: a magnetic resonance spectroscopy device to obtain the level of the spectral signal at 3.15 and 3.19 ppm, within the breast tissue of the subject, and a comparator for comparing the level of the spectral signal obtained with a reference level of a spectral signal at 3.15 and 3.19 ppm from the breast of a healthy subject, to determine whether the level of the signal obtained exceeds the reference level of a healthy subject, is comparable to that of a subject known to be at elevated risk, or is elevated to the level of persons known to be carrying a gene mutation.

The spectral signal at 3.15 and 3.19 ppm may be that of methylmalonic acid (MM A). The spectral signal may be obtained using 2D COrelated SpectroscopY (2D COSY) or by datamining ID MRS. The spectral signal may be obtained using data mining of a ID MRS signal. The results may be compared to an International Breast cancer Intervention Study (IBIS) score of the subject.

The invention provides a method enabling a determination of the risk of developing breast cancer of a subject, comprising: processing spectral data obtained from breast tissue of the subject using a magnetic resonance spectroscopy device to obtain the level of the spectral signal at 3.15 and 3.19 ppm, and comparing the level of the spectral signal obtained with a reference level of a spectral signal at 3.15 and 3.19 ppm from the breast of a healthy subject, to determine whether the level of the signal obtained exceeds the reference level of a healthy subject; is comparable to that of a subject known to be at elevated risk; or is elevated to the level of persons known to be carrying a gene mutation.

The spectral signal at 3.15 and 3.19 ppm may be that of methylmalonic acid (MM A). The spectral signal may be obtained using 2D COrelated SpectroscopY (2D COSY). The spectral signal may be obtained using data mining of a ID MRS signal. The results may be compared to an International Breast cancer Intervention Study (IBIS) score of the subject.

The invention provides a system for enabling a determination of the risk of developing breast cancer of a subject, comprising: a processor for processing spectral data obtained from the breast tissue of the subject using a magnetic resonance spectroscopy device to obtain the level of the spectral signal at 3.15 and 3.19 ppm, and a comparator for comparing the level of the spectral signal obtained with a reference level of a spectral signal at 3.15 and 3.19 ppm from the breast of a healthy subject, to determine whether the level of the signal obtained exceeds the reference level of a healthy subject, is comparable to that of a subject known to be at elevated risk, or is elevated to the level of persons known to be carrying a gene mutation.

DESCRIPTION OF THE DRAWING FIGURES

Figure 1 shows the chemical structure of Methylmalonic acid (2-methylpropanedioic acid).

Figure 2 shows a three-dimensional image of a 2D COSY breast spectrum from an apparently healthy premenopausal woman with a dense breast density of BIO-RADS 3. The area marked is the rectangular region shown in Figure 3.

Figure 3 shows a contour plot of the expanded region F2/F1 of Figure 2. : 3.00ppm to 3.90ppm of a COSY recorded from a premenopausal woman with dense breast tissue. Contour plots demonstrate proton MR spectroscopy resonances, with tentative assignments for the MMA multiplet at 3.15 and 3.19ppm, Other diagonal resonances are Gly: Glycerol; GPC: Glycerophosphocholine; Gly: Glycine; Glc: Glucose; Gin: Glutamine; Glu: Glutamate; His: Histidine; m-Ins: Myo-inositol; scyllo-Inositol; Tau: Taurine; Thr: Threonine; TBC: to be confirmed. Figure 4 shows the level of the resonances assigned to MMA at 3.15 and 3.19ppm plotted against the IBIS score for each patient group. It can be seen that the respective levels of these MMA resonances are correlated to the IBIS score.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

A preferred embodiment of the invention will be described, but the invention is not limited to this embodiment.

A 2D COSY from a woman with breast density of BI-RADS 3 is shown in Figure 2. The lipid assignments fire as described in Ramadan et al ⁸ . A contour plot of the expanded region F2/F1: 3.00ppm to 3.90ppm is shown in Figure 3 where resonances at 3.15 and 3.19ppm are apparent and consistent with the presence of the MMA molecule. The second multiplet of MMA at 1.23ppm is not visible due to the large methylene resonance from fatty acyl chains ² . However, the crosspeak at 1.27- 3.20ppm showing scalar coupling of the methyl protons and methyne protons of MMA can also be recorded.

The intensity of these diagonal resonances was measured for all categories of women studied i.e. healthy women with no known risk for cancer; those at familial cancer risk; and those carrying the BRCA1 or BRCA2 gene mutation. All were evaluated for risk based on the IBIS score. These are shown in Figure 3 where the level of the MMA recorded is directly correlated by the IBIS score.

The reason why women with dense breast tissue who are premenopausal have an elevated risk for breast cancer has remained a mystery and of concern. Breast density alone is not sufficient to render high risk for breast cancer. Here we tentatively assign resonances at 3.15 and 3.19ppm to MMA. Other contenders for this assignment are tyrosine at 3.19ppm and homocarnosine at 3.18ppm but neither have the other resonances expected from that molecule in the spectra.

MMA, has recently reported to endow cancer cells with the properties necessary to migrate, invade, survive and thrive as metastatic lesions ¹ . The report evaluates the aging population and suggests that MMA relies on the activation of TGFP signaling in an autocrine fashion to induce SOX4 and consequently the transcriptional reprogramming necessary for the cellular plasticity that sustains tumor progression. If this assignment is correct, then this provides another piece in the puzzle as to why premenopausal women with dense breasts are at higher risk for breast cancer. Proof of assignment of these resonances can be made by chemical evaluation of breast tissue extractions to confirm the presence of MMA in the dense premenopausal breast tissue.

The capacity to non-invasively monitor breast tissue chemistry changes at a molecular level, using in vivo two-dimensional magnetic resonance spectroscopy, in an apparently healthy breast, shows great potential for the development of a personalised medicine approach. This is particularly relevant in the cohort of women with a family history that increases their lifetime risk of developing breast cancer, but without any other risk factor that places them in the group at greater than 20 percent lifetime risk.

This is the cohort in which the American Cancer Society does not recommend annual screening using dynamic contrast-enhanced MRI, but in which other modalities do not provide a sensitive or specific enough approach.

While the data were obtained using 2D COSY, it is possible that this information may be deduced using ID MRS and datamining procedures as developed for pain ⁹ . These resonances may be recorded and measured using a full 2D data set or a specific range of delays that encompass the strongest signal for the MMA.

In conclusion, using in vivo MR spectroscopy two resonances can be searched for at 3.15 and 3.19ppm in breast tissue. If the resonances are present, they are consistent with the presence of the MMA molecule in breast tissue. In healthy women, with no significant family history, those with highly dense breast tissue have five times higher levels of MMA than those with low breast density. In those women with an elevated risk of cancer, as judged by their IBIS score, the MMA is highest in those carrying the BRCA gene mutations. The amount of these two resonances, recorded at 3.15 and 3.19ppm, increase linearly with the risk of breast cancer as deduced by the IBIS risk score. While the assignment of these resonances to MMA is only tentative at this stage, regardless of the exact assignment of the resonances, it appears that they correlate with lifetime risk of developing breast cancer, as measured using the IBIS score. Datamining of in vivo ID MRS of breast tissue can be done to determine whether the MMA information can be extracted from a much shorter acquisition time in a scanner. References

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