Optical scattering as an early marker of apoptosis during chemotherapy and antiangiogenic therapy in murine models of prostate and breast cancer

Prediction of axillary lymph node metastasis in T1 breast cancer using diffuse optical tomography, strain elastography and molecular markers

Background

Early-stage breast cancer (BC) presents a certain risk of axillary lymph node (ALN) metastasis (ALNM), leading to different individualized treatment. Preoperative non-invasive prediction to determine ALN status is of great significance for avoiding ineffective axillary surgery. Tumor total hemoglobin concentration (TTHC), strain ratio (SR), and Ki-67 expression are associated with ALNM in BC, but few studies have focused on T1 BC. This study aimed to explore the usefulness of these factors individually and in combination for the preoperative prediction of ALNM in T1 BC.

Methods

This was a cross-sectional study. A total of 122 patients with T1 BC were enrolled. TTHC and SR were assessed preoperatively using diffuse optical tomography and strain elastography, respectively. All patients were pathologically evaluated to determine ALN status. Univariate analysis and logistic regression trend test were performed to identify independent predictors. A combined model of imaging-pathological parameters for ALNM was developed.

Results

Histopathological analysis indicated that 56 patients (45.9%) exhibited ALNM. The fully adjusted model demonstrated a significant trend correlating increased TTHC (P<0.01 for trend), SR (P<0.001 for trend), and Ki-67 expression (P=0.004 for trend) with ALNM. The area under the receiver operating characteristic curves (AUCs) of TTHC, SR, and Ki-67 expression for predicting ALNM were 0.707 [95% confidence interval (CI): 0.61-0.80], 0.718 (95% CI: 0.63-0.81) and 0.642 (95% CI: 0.56-0.73), respectively. The integration of imaging parameters (TTHC and SR) and Ki-67 expression yielded superior predictive performance for ALN status compared to each parameter individually, as evidenced by an AUC of 0.837 (95% CI: 0.76-0.91). The Hosmer-Lemeshow test P value was 0.880, demonstrating good calibration. In the subgroup analysis, the model exhibited positive predictive capabilities (AUC >0.75) across various subgroups, including molecular subtype, pathological type, and grade. Notably, the predictive performance was particularly enhanced in patients with invasive lobular carcinomas and triple-negative BC, with AUC values exceeding 0.90 for both subgroups.

Conclusions

The study found that TTHC ≥185.75 µmol/L, SR ≥3.93 and Ki-67 expression ≥20% were strongly associated with ALNM in patients with T1 BC. The combined imaging-pathological model might provide a convenient preoperative method for predicting ALN status, which can assist clinicians in individualizing management for patients with early-stage BC.

Design and Validation of a Multimodal Diffuse Reflectance and Spatially Offset Raman Spectroscopy System for In Vivo Applications

We report on the development of a multimodal spectroscopy system, combining diffuse reflectance spectroscopy (DRS) and spatially offset Raman spectroscopy (SORS). A fiber optic probe was designed with spatially offset source-detector fibers to collect subsurface measurements for each modality, as well as ball lens-coupled fibers for superficial measurements. The system acquires DRS, zero-offset Raman spectroscopy (RS) and SORS with good signal-to-noise ratio. Measurements on chicken breast tissue demonstrate that both DRS and RS can acquire spectra from similar depths within tissue. Measurements acquired from the skin of a human volunteer demonstrate distinct Raman peaks at 937 and 1755 cm-1 that were unique to the zero-offset ball lens configuration and 718 and 1089 cm-1 for the spatially offset setting. We also identified Raman peaks corresponding to melanin that were prominent in the superficial measurements obtained with the ball lens-coupled fibers but not in the spatially offset fibers.

Spatial frequency domain imaging for the assessment of scleroderma skin involvement

Systemic sclerosis (SSc) is an autoimmune disease characterized by the widespread deposition of excess collagen in the skin and internal organs, as well as vascular dysfunction. The current standard of care technique used to quantify the extent of skin fibrosis in SSc patients is the modified Rodnan skin score (mRSS), which is an assessment of skin thickness based on clinical palpation. Despite being considered the gold standard, mRSS testing requires a trained physician and suffers from high inter-observer variability. In this study, we evaluated the use of spatial frequency domain imaging (SFDI) as a more quantitative and reliable method for assessing skin fibrosis in SSc patients. SFDI is a wide-field and non-contact imaging technique that utilizes spatially modulated light to generate a map of optical properties in biological tissue. The SFDI data were collected at six measurement sites (left and right forearms, hands, and fingers) of eight control subjects and ten SSc patients. mRSS were assessed by a physician, and skin biopsies were collected from subject's forearms and used to assess for markers of skin fibrosis. Our results indicate that SFDI is sensitive to skin changes even at an early stage, as we found a significant difference in the measured optical scattering (μs') between healthy controls and SSc patients with a local mRSS score of zero (no appreciable skin fibrosis by gold standard). Furthermore, we found a strong correlation between the diffuse reflectance (R_d) at a spatial frequency of 0.2 mm^-1 and the total mRSS between all subjects (Spearman correlation coefficient = -0.73, p-value < 0.0028), as well as high correlation with histology results. The healthy volunteer results show excellent inter- and intra-observer reliability (ICC > 0.8). Our results suggest that the measurement of tissue μs' and R_d at specific spatial frequencies and wavelengths can provide an objective and quantitative assessment of skin involvement in SSc patients, which could greatly improve the accuracy and efficiency of monitoring disease progression and evaluating drug efficacy.

Diffuse Reflectance Spectroscopy of Changes in Tumor Microenvironment in Response to Different Doses of Radiation

Radiation therapy plays an important role in cancer treatment, as it is an established method used as part of the treatment plan for the majority of cancer patients. Real-time monitoring of the effects of radiation on the tumor microenvironment can contribute to the development of better treatment plans. In this study, we use diffuse reflectance spectroscopy, a non-invasive optical fiber-based technique, to determine the effects of different doses of radiation on the tumor microenvironment, as well as to determine the sensitivity of diffuse reflectance spectroscopy to low doses of radiation that are used in the treatment of certain cancers. We injected 4T1 cells into 50 Balb/c mice to generate tumor xenografts. When the tumors grew to 200 mm3, we distributed the mice into a control group or one of three radiation groups: 1, 2, or 4 Gy/fraction, and they underwent treatment for five consecutive days. We measured the tumor volume and collected diffuse reflectance spectra every day, with optical measurements being acquired both before and one h postirradiation on the five days of treatment. Based on the diffusely reflected light, we quantified vascular oxygenation, total hemoglobin content, and tissue scattering within these tumors. There was a significant increase in tumor vascular oxygenation, which was primarily due to an increase in oxygenated hemoglobin, in response to a 1 Gy/fraction of radiation, while there was a decrease in tissue scattering in response to all doses of radiation. Immunohistochemical analysis revealed that tumor cell proliferation and apoptosis were higher in irradiated groups compared to the control group. Our findings show that diffuse reflectance spectroscopy is sensitive to microenvironmental changes in tumors treated with doses of radiation as low as 1 Gy/fraction.

Metronomic Chemotherapy for Metastatic Breast Cancer Treatment: Clinical and Preclinical Data between Lights and Shadows

Metronomic chemotherapy (mCHT), defined as continuous administration of low-dose chemotherapeutic agents with no or short regular treatment-free intervals, was first introduced to the clinic in international guidelines in 2017, and, since then, has become one of the available strategies for the treatment of advanced breast cancer (ABC). Despite recent successes, many unsolved practical and theoretical issues remain to be addressed. The present review aims to identify the "lights and shadows" of mCHT in preclinical and clinical settings. In the preclinical setting, several findings indicate that one of the most noticeable effects of mCHT is on the tumor microenvironment, which, over the last twenty years, has been demonstrated to be pivotal in supporting tumor cell survival and proliferation. On the other hand, the direct effects on tumor cells have been less well-defined. In addition, critical items to be addressed are the lack of definition of an optimal biological dose (OBD), the method of administration of metronomic schedules, and the recognition and validation of predictive biomarkers. In the clinical context-where mCHT has mainly been used in a metastatic setting-low toxicity is the most well-recognised light of mCHT, whereas the type of study design, the absence of randomised trials and uncertainty in terms of doses and drugs remain among the shadows. In conclusion, growing evidence indicates that mCHT is a suitable treatment option for selected metastatic breast cancer (MBC) patients. Moreover, given its multimodal mechanisms of action, its addition to immunological and targeted therapies might represent a promising new approach to the treatment of MBC. More preclinical data are needed in this regard, which can only be obtained through support for translational research as the key link between basic science and patient care.

Spatial frequency domain imaging for monitoring immune-mediated chemotherapy treatment response and resistance in a murine breast cancer model

Spatial Frequency Domain Imaging (SFDI) can provide longitudinal, label-free, and widefield hemodynamic and scattering measurements of murine tumors in vivo. Our previous work has shown that the reduced scattering coefficient (μ's) at 800 nm, as well as the wavelength dependence of scattering, both have prognostic value in tracking apoptosis and proliferation during treatment with anti-cancer therapies. However, there is limited work in validating these optical biomarkers in clinically relevant tumor models that manifest specific treatment resistance mechanisms that mimic the clinical setting. It was recently demonstrated that metronomic dosing of cyclophosphamide induces a strong anti-tumor immune response and tumor volume reduction in the E0771 murine breast cancer model. This immune activation mechanism can be blocked with an IFNAR-1 antibody, leading to treatment resistance. Here we present a longitudinal study utilizing SFDI to monitor this paired responsive-resistant model for up to 30 days of drug treatment. Mice receiving the immune modulatory metronomic cyclophosphamide schedule had a significant increase in tumor optical scattering compared to mice receiving cyclophosphamide in combination with the IFNAR-1 antibody (9% increase vs 10% decrease on day 5 of treatment, p < 0.001). The magnitude of these differences increased throughout the duration of treatment. Additionally, scattering changes on day 4 of treatment could discriminate responsive versus resistant tumors with an accuracy of 78%, while tumor volume had an accuracy of only 52%. These results validate optical scattering as a promising prognostic biomarker that can discriminate between treatment responsive and resistant tumor models.

Type-I interferon signaling is essential for robust metronomic chemo-immunogenic tumor regression in murine breast cancer

Many patients with breast cancer have a poor prognosis with limited therapeutic options. Here, we investigated the potential of chemo-immunogenic therapy as an avenue of treatment. We utilized two syngeneic mouse mammary tumor models, 4T1 and E0771, to examine the chemo-immunogenic potential of cyclophosphamide and the mechanistic contributions of cyclophosphamide-activated type-I interferon (IFN) signaling to therapeutic activity. Chemically-activated cyclophosphamide induced robust IFNα/β receptor-1-dependent signaling linked to hundreds of IFN-stimulated gene responses in both cell lines. Further, in 4T1 tumors, cyclophosphamide given on a medium-dose, 6-day intermittent metronomic schedule induced strong IFN signaling but comparatively weak immune cell infiltration associated with long-term tumor growth stasis. Induction of IFN signaling was somewhat weaker in E0771 tumors but was followed by widespread downstream gene responses, robust immune cell infiltration and extensive, prolonged tumor regression. The immune dependence of these effective anti-tumor responses was established by CD8 T-cell immunodepletion, which blocked cyclophosphamide-induced E0771 tumor regression and led to tumor stasis followed by regrowth. Strikingly, IFNα/β receptor-1 antibody blockade was even more effective in preventing E0771 immune cell infiltration and blocked the major tumor regression induced by cyclophosphamide treatment. Type-I IFN signaling is thus essential for the robust chemo-immunogenic response of these tumors to cyclophosphamide administered on a metronomic schedule.

Simple demodulation method for optical property extraction in spatial frequency domain imaging

Different demodulation methods affect the efficiency and accuracy of spatial frequency domain imaging (SFDI). A simple and effective method of sum-to-product identities (STPI) demodulation was proposed in this study. STPI requires one fewer image than conventional three-phase demodulation (TPD) at a spatial frequency. Numerical simulation and phantom experiments were performed. The result proved the feasibility of STPI and showed that STPI combined with subtraction can achieve high-precision demodulation in the low spatial frequency domain. Through extraction of phantom optical properties, STPI had similar accuracy compared with other demodulation methods in extracting optical properties in phantoms. STPI was also used to extract the optical properties of milk, and it had highly consistent results with TPD, which can distinguish milk with different fat content. The demodulation effect of this method in the low spatial frequencies is better than other fast demodulation methods.