Stimulated Raman Imaging Maps Hidden Bone Damage Around Cancer Metastases

When cancer spreads to bone, the damage is rarely uniform. Tumor cells remodel the skeleton in patchwork fashion, building abnormal new bone in some regions while destroying it in others, and clinicians have long struggled to measure that chemical patchwork with precision. A new study published in the Annals of Biomedical Engineering shows that a laser-based imaging technique called stimulated Raman scattering spectromicroscopy can map those biochemical differences across metastatic bone with spatial resolution that conventional methods cannot match, revealing changes not only where tumor cells reside but also in bone far removed from the lesion itself.

The research, led by Azin Mirzajavadkhan, Christian Chum Him Lai, Margarete K. Akens, Cari M. Whyne, and Chenxi Qian at the University of Toronto and Sunnybrook Research Institute, focused on mixed femoral metastases, a model of the osteolytic and osteoblastic lesions that complicate advanced prostate, breast, and lung cancers. Mixed lesions are particularly treacherous because they combine bone destruction and bone formation within the same anatomical site, producing tissue whose mechanical quality varies dramatically over distances of less than a millimeter. Standard analytical tools, such as bulk Raman spectroscopy or micro-computed tomography, average over those gradients or measure structure without chemistry, leaving the local composition of tumor-adjacent and tumor-distant bone largely unexplored.

Stimulated Raman scattering offers a way around that limitation. Unlike spontaneous Raman spectroscopy, which collects weak inelastic scattering from a laser spot and can require long acquisition times, stimulated Raman scattering uses two synchronized lasers to excite molecular vibrations directly, amplifying the signal by many orders of magnitude. The result is rapid, label-free imaging of specific chemical bonds: amide I and amide III vibrations report on the protein matrix of bone, proline signals trace collagen deposition, phenylalanine marks aromatic amino acid content, and phosphate bands quantify the mineral phase. Because the technique requires no stains, dyes, or decalcification, the same tissue can be interrogated in a near-native state.

To test the approach, the team induced mixed metastases in five- to six-week-old athymic male rats by intracardiac injection of ACE-1 canine prostate cancer cells, a well-characterized preclinical model of osteoblastic-dominant mixed lesions. Twenty-one days after inoculation, the researchers harvested both femora. Sagittal sections of the right femora were processed for histological analysis and stimulated Raman imaging of the organic phase, while undecalcified sections preserved the mineral phase for separate assessment. Regions of interest were then selected within newly formed osteoblastic bone, within bone distant from the tumor, and in distinct samples containing only healthy bone, allowing direct comparison of chemistry across the metastatic landscape.

The measurements revealed a striking biochemical signature in the osteoblastic regions. Compared with healthy bone, the newly formed tumor-associated tissue showed increased signal intensity for amide I, amide III, and proline, indicating enhanced collagen deposition, alongside reduced phosphate and phenylalanine signals, reflecting diminished mineral content and altered protein composition. In practical terms, the tumor-driven bone formation produced a matrix that was collagen-rich but under-mineralized, a combination known to compromise stiffness and fracture resistance. Because mineral-to-matrix ratio is one of the strongest Raman predictors of bone mechanical quality, the finding suggests that even bone that appears to be growing in response to cancer may be structurally inferior to healthy tissue.

Perhaps the more provocative result came from the bone far from the tumor. In regions with no direct tumor involvement, the researchers measured elevated proline and reduced phenylalanine signal intensity, a pattern consistent with systemic perturbation of collagen composition. This supports the study’s central hypothesis: that interactions between tumor and bone influence bone quality beyond the areas of direct tumor involvement. If cancer cells can reprogram the chemistry of bone they have not yet colonized, the implications for fracture risk assessment are significant, because current clinical imaging evaluates lesion geometry rather than the biochemical integrity of the surrounding skeleton.

The findings build on a growing body of Raman-based bone research. Earlier work by several of the same investigators showed that osteolytic and mixed metastases modulate collagen and mineral parameters in rat vertebral bone, and independent studies in mouse models of prostate and breast cancer metastasis demonstrated that tumors alter bone mineral and matrix composition independently of effects on bone architecture. What the new study adds is spatially resolved, quantitative chemical mapping of the organic and mineral phases in mixed femoral lesions, achieved non-destructively and without the exogenous labels that can perturb tissue chemistry.

The technical achievement rests on the maturity of stimulated Raman scattering microscopy itself, which has matured rapidly over the past decade as a biological imaging platform. Recent applications include hyperspectral imaging of microcalcifications in fresh breast biopsies and high-content stimulated Raman histology of human breast cancer, where the technique distinguishes tumor from stroma without section staining. Applying the method to bone required careful handling of the mineral phase, since undecalcified sections preserve hydroxyapatite but are harder to prepare, and the organic phase signals must be disentangled from the strong phosphate background. The Toronto team’s dual-section strategy, using decalcified sections for organic phase imaging and undecalcified sections for mineral assessment, provided a practical route to characterizing both components of the bone matrix.

For clinicians, the study points toward a future where bone quality in metastatic disease could be assessed chemically rather than merely structurally. Skeletal metastases are a leading cause of morbidity in advanced cancer, producing pain, fracture, and spinal cord compression, and treatment decisions, from bisphosphonates to stereotactic body radiation therapy to surgical stabilization, depend on judgments about how much load the compromised bone can bear. A label-free imaging modality that quantifies collagen deposition, mineral content, and protein composition at the microscopic level could eventually inform those decisions, identifying regions of bone that look intact on a CT scan but are biochemically weakened, or vice versa.

The authors caution that the work is preclinical, conducted in a rat model with approval from the institutional animal care committee at University Health Network in Toronto, and that translation to human diagnostics will require further validation. Data supporting the findings are stored at Sunnybrook Research Institute and may be available from the corresponding author under reasonable request. Still, the study establishes stimulated Raman scattering microscopy as a non-destructive tool for detecting spatially resolved biochemical alterations in metastatic bone, and it demonstrates that the chemical footprint of cancer extends beyond the visible margins of the tumor. As the technique matures, the patchwork of metastatic bone, long invisible to conventional imaging, may finally come into focus.

Subject of Research: Stimulated Raman scattering spectromicroscopy reveals biochemical heterogeneity of bone quality in mixed femoral metastases.

Article Title: Bone Quality Heterogeneity in Mixed Femoral Metastases Revealed by Stimulated Raman Scattering Spectromicroscopy

Article References: Bone Quality Heterogeneity in Mixed Femoral Metastases Revealed by Stimulated Raman Scattering Spectromicroscopy. (n.d.). https://doi.org/10.1007/s10439-026-04433-x

Image Credits: AI Generated

DOI: 10.1007/s10439-026-04433-x

Keywords: bone metastases, stimulated Raman scattering, bone quality, osteoblastic lesions, collagen, bone mineralization, femur, prostate cancer, Raman spectroscopy, cancer biology, biomedical imaging, Bone