Prediction of Metastasis Using Second Harmonic Generation
Posted March 17, 2017
Edward Brown, Ph.D., University of Rochester
Understanding the Role of Matrix Microstructure in Breast Tumors In Order to Predict Metastasis Using Second Harmonic Generation
Edward Brown, Ph.D., University of Rochester
It is estimated that only 40% of the more than 80% of breast cancer patients who are treated with adjuvant chemotherapy relapse and ultimately die of metastatic disease. Therefore, many women who could receive local treatment (e.g. surgery and radiotherapy) alone, but are given adjuvant chemotherapy and exposed to the toxic side effects needlessly, are considered over-treated.1 Being able to determine which patients would derive benefit from adjuvant chemotherapy at initial diagnosis would aid clinicians in determining the best treatment regimen for a given patient. Currently, there are no definitive ways to evaluate the primary tumor characteristics in order to stratify patients and determine whether they will develop recurrent metastatic tumors later in life and thus possibly benefit from adjuvant chemotherapy. Metastatic potential can be estimated, however, through the examination of primary tumor gene and protein expression using such tests as OncotypeDX and immunohistochemical analyses of tumor biopsies, respectively. However, these methods are "tumor-centric," and may not take the microenvironment surrounding the tumor into sufficient account.
Dr. Edward Brown received a 2008 Era of Hope Scholar expansion award to develop a "matrix-focused" approach that would complement the "tumor-centric" models for predicting metastatic potential of estrogen receptor positive (ER+), lymph node-negative (LNN) breast tumors. Dr. Brown proposed to use second harmonic generation (SHG), a high-resolution optical microscopy technique, to quantitatively analyze tumor collagen structural changes that occur during tumor progression. Collagen, a key component of the extracellular matrix, has been shown to produce intrinsic SHG signals.2 Work supported by this award and published by Dr. Brown and his team at the University of Rochester has shown that SHG directionality, measured by the ratio of forward-propagating to backward-propagating signal (F/B ratio), can be used to monitor the changes in collagen fibril diameter, spacing, and order as tumors progress. In a paper published in the Journal of Biomedical Optics,3 Dr. Brown used tissue microarray (TMA) slides and showed that the F/B ratio measured in tumors that were diagnosed as ductal carcinoma in situ (DCIS) did not differ from healthy tissue samples. However, the F/B ratio was shown to decrease in patients diagnosed with invasive ductal carcinoma (IDC). Among the IDC tumor samples, the F/B ratio was shown to significantly decrease as tumors progress from Grade 1 to Grade 2 and remained low for Grade 3 tumors.
Subsequently, in a retrospective analysis of 125 ER+ LNN breast tumor samples from women who had not received any neoadjuvant or adjuvant treatment (obtained from the Erasmus Medical Center; Rotterdam, Netherlands), Dr. Brown was able to show that the F/B ratio can be used to stratify patients based on their potential for tumor aggressiveness. This work, published in BMC Cancer,4 demonstrated that patients whose primary tumors have a lower F/B ratio had a shorter metastasis-free survival (MFS) and a worse overall survival (OS), while those patients whose tumors had a high F/B ratio had a longer MFS and a better OS. Further studies were done in a subset of patients from this cohort who received tamoxifen as a first-line treatment for recurrence and who later developed metastases. To determine whether the F/B ratio of the primary tumor was predictive of progression-free survival (PFS), Dr. Brown analyzed the F/B ratio from those patients with recurrent disease. Surprisingly, results showed that patients with low F/B ratios in their primary tumor had longer PFS, compared to patients whose primary tumor samples had a high F/B ratio at initial diagnosis. This surprising result suggested that differences in the primary tumor collagen microstructure could affect the mechanism by which tumor cells disseminate, thus altering tumor cell susceptibility to later treatment.
Based on the results of these publications and supported by his 2008 Era of Hope expansion award, Dr. Brown was able to obtain a provisional patent application (61/977,618) titled, "Method and apparatus to diagnose metastatic and progressive potential of cancer, fibrosis, and other diseases." This patent application covers the method (two-photon laser-scanning microscope used to capture SHG images) invented for determining the metastatic potential from tissue samples (i.e., biopsy) of a disease, including but not limited to breast cancer. HarmonigenicTM Corporation (http://www.harmonigenic.com/) has retained the option for this patent. They plan on using this patent to help guide the use of SHG-generated F/B ratios into clinical trials of ER+ LNN breast cancer patients with the hope of providing clinicians with an additional diagnostic tool. If successful, this method has the opportunity to improve the quality of life and lower the overall cost of treatment for many breast cancer patients. If clinicians are able to determine which patients would benefit from receiving adjuvant chemotherapy at diagnosis, they could reduce overtreatment and spare women who would have otherwise not benefitted from chemotherapy.
1 Weigelt B, Peterse JL and van’t Veer LJ. 2005. Breast cancer metastasis: markers and models. Nature Rev Cancer 5:591-602.
2 Burke KA, Dawes RP, Cheema MK, van Hove A, Benoit DS, Perry SW, and Brown E. 2015. Second-harmonic generation scattering directionality predicts tumor cell motility in collagen gels. J Biomed Opt 20(5):051024.
3 Burke K, Tang P and Brown E. 2013. Second harmonic generation reveals matrix alterations during breast tumor progression. J Biomed Opt 18(3):31106.
4 Burke K, Smid M, Dawes RP, Timmermans MA, Salzman P, van Deurzen CHM, Beer DG, Foekens JA, and Brown E. 2015. Using second harmonic generation to predict patient outcome in solid tumors. BMC Cancer 15:929.
Brown E, Perry S, Burke K, Kottmann M, Sime P and Sharp J. 2014. Method and apparatus to diagnose metastatic and progressive potential of cancer, fibrosis, and other diseases. Provisional Patent Application 61/977,618.
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