Assessment of treatment response during chemoradiation therapy for pancreatic cancer based on quantitative radiomic analysis of daily CTs: An exploratory study

Abstract

PurposeIn an effort for early assessment of treatment response, we investigate radiation induced changes in quantitative CT features of tumor during the delivery of chemoradiation therapy (CRT) for pancreatic cancer. MethodsDiagnostic-quality CT data acquired daily during routine CT-guided CRT using a CT-onrails for 20 pancreatic head cancer patients were analyzed. On each daily CT, the pancreatic head, the spinal cord and the aorta were delineated and the histograms of CT number (CTN) in these contours were extracted. Eight histogram-based radiomic metrics including the mean CTN (MCTN), peak position, volume, standard deviation (SD), skewness, kurtosis, energy and entropy were calculated for each fraction. Paired t-test was used to check the significance of the change of specific metric at specific time. GEE model was used to test the association between changes of metrics over time for different pathology responses. ResultsIn general, CTN histogram in the pancreatic head (but not in spinal cord) changed during the CRT delivery. Changes from the 1 st to the 26 th fraction in MCTN ranged from -15.8 to 3.9HU with an average of -4.7 HU (p<0.001). Meanwhile the volume decreased, the skewness increased (less skewed), and the kurtosis decreased (less peaked). Data Availability Statement: All relevant data are within the paper. Funding:The authors received no specific funding for this work. Competing interests:The authors have declared that no competing interests exist.pathological response is associated with the changes of MCTN, SD, and skewness. In cases of good response, patients tend to have large reductions in MCTN and skewness, and large increases in SD and kurtosis. ConclusionsSignificant changes in CT radiomic features, such as the MCTN, skewness, and kurtosis in tumor were observed during the course of CRT for pancreas cancer based on quantitative analysis of daily CTs. These changes may be potentially used for early assessment of treatment response and stratification for therapeutic intensification.

Technical Note: Enhancing soft tissue contrast and radiation‐induced image changes with dual‐energy CT for radiation therapy

“…Secondly, it sought to measure the amplification of the CT texture‐based treatment response signal during pancreatic cancer RT from low‐energy MEI relative to traditional PEI. As reported previously, the radiation‐induced CT texture changes during chemo‐RT for pancreatic cancer correlated with tumor pathological response, although the changes were generally small from the conventional 120 kVp CTs . We seek to demonstrate that low‐energy MEI will increase the magnitude of the signal and thus make the radiation‐induced changes in CT textures easier to detect during fractionated treatment.…”

“…). Histogram features can vary during fractionated treatment and have been correlated with histological outcome for pancreas cancer patients . The amplification of this change for a single patient via low‐energy MEI is immediately evident in Fig.…”

“…Specifically for pancreas cancers, the response signal may be difficult to distinguish from noise after the first few weeks of treatment using standard CT. The change in PEI CT intensity after completing therapy is only expected to be on the order of 5 HU for pancreatic tumors . During early fractions, the change would be expected to be even less than that, and thus may be inadequate to motivate adaptive planning.…”

“…Beyond simply improving the image quality, low‐energy MEI could potentially improve the use of CT for treatment response assessment due to its superior sensitivity to the change in material composition. It has been reported that radiation can induce changes in CT texture features during RT of several cancers including pancreas, head and neck, lung, and liver . Quantitative data extracted from daily CTs acquired during IGRT using in‐room CT, such as changes in CT textures (histogram or higher order features) may be used to assess radiation treatment response .…”

“…Lesions embedded in soft tissue, such as the pancreas, are difficult to detect with CT because the soft tissue contrast is inadequate and hence the treatment response signal is relatively small. On average a change in 4.7 HU on MCTN in the pancreas is reported between the first week and last week of therapy based on conventional 120 kVp CTs, which is almost 10 times larger than the standard deviation of the MCTN of water for this scanner . In comparison to traditional PEI CTs, we investigated how low x‐ray energy MEI CT enhances the soft tissue contrast and thus amplifies the signal of radiation‐induced changes in CT textures.…”