Comparison of volumetric dynamic optical coherence tomography with biological methods for evaluation of radiation effects in prostate tumor spheroids.

SIGNIFICANCE: Three-dimensional (3D) tumor spheroids are more physiologically representative of in vivo patient tumors compared with two-dimensional monolayer culture. However, their 3D nature challenges the use of conventional biological techniques such as proliferation assays, fluorescence microscopy, and the clonogenic assay, which is the gold standard method for assessing cell survival following radiation. However, the clonogenic assay requires spheroid disaggregation.

AIM: Non-invasive volumetric imaging with dynamic optical coherence tomography (dOCT) enables cellular activity to be visualized with spatial resolution within 3D tumor spheroids. Cellular activity observed via dOCT in irradiated prostate tumor spheroids was quantified for comparison with conventional biological techniques.

APPROACH: A Varian TrueBeam linear accelerator was used to irradiate spheroid and monolayer cultures with a 6-MV beam. Cellular activity was estimated from dOCT images generated via frequency banding and compared with clonogenic assay, proliferation assay, fluorescence microscopy, and 3D cell simulation.

RESULTS

Prostate cancer cells cultured as spheroids demonstrated improved radio-resistance via clonogenic assay compared with monolayer culture. The dOCT method demonstrated quantitative and qualitative agreement with the proliferation assay and fluorescence microscopy, respectively.

CONCLUSIONS

A longer duration of repeated dOCT measurement in tumor spheroids following radiation treatment could offer a non-invasive alternative to the clonogenic assay.