Elsevier

Radiotherapy and Oncology

Volume 102, Issue 2, February 2012, Pages 239-245
Radiotherapy and Oncology

PET in lung cancer
Combined PET/CT image characteristics for radiotherapy tumor response in lung cancer

https://doi.org/10.1016/j.radonc.2011.10.014Get rights and content

Abstract

Background and Purpose

Prediction of local failure in radiotherapy patients with non-small cell lung cancer (NSCLC) remains a challenging task. Recent evidence suggests that FDG–PET images can be used to predict outcomes. We investigate an alternative multimodality image-feature approach for predicting post-radiotherapy tumor progression in NSCLC.

Material and methods

We analyzed pre-treatment FDG–PET/CT studies of twenty-seven NSCLC patients for local and loco-regional failures. Thirty-two tumor region features based on SUV or HU, intensity-volume-histogram (IVH) and texture characteristics were extracted. Statistical analysis was performed using Spearman’s correlation (rs) and multivariable logistic regression.

Results

For loco-regional recurrence, IVH variables had the highest univariate association. In PET, IVH-slope reached rs = 0.3426 (p = 0.0403). Motion correction slightly improved correlation of texture features. In CT, coefficient of variation had the highest association rs = −0.2665 (p = 0.0871). Similarly for local failure, a CT-IVH parameter reached rs = 0.4530 (p = 0.0105). For loco-regional and local failures, a 2-parameter model of PET-V80 and CT-V70 yielded rs = 0.4854 (p = 0.0067) and rs = 0.5908 (p = 0.0013), respectively. Addition of dosimetric variables provided improvement in cases of loco-regional but not local failures.

Conclusions

We proposed a feature-based approach to evaluate radiation tumor response. Our study demonstrates that multimodality image-feature modeling provides better performance compared to existing metrics and holds promise for individualizing radiotherapy planning.

Section snippets

Patient population

The study was approved by the Washington University School of Medicine Institutional Review Board. Patients with new diagnosis of NSCLC confined to the thorax who had not previously received thoracic irradiation were candidates for definitive therapy with either conventionally fractionated radiation therapy (RT) or stereotactic body radiosurgery (SBRT) as a component of their treatment and had an archived treatment plan, were eligible to participate. Patients were treated between 2003 and 2007

Experimental results

For 27 patients, thirty-two variables were extracted from both PET and CT pre-treatment images. The univariate correlations between PET/CT features and clinical endpoints of loco-regional or local control have been summarized in Table 2, Table 3 and Supplementary Figure S2.

For loco-regional recurrence, IVH variables had a high correlation with treatment outcomes over a wide range of values (x) as shown in the Supplementary Figure. For PET features without motion correction, IVH slope had the

Discussion

Our ability to cure patients with locally advanced NSCLC is severely limited by our ability to control disease locally. As a result, more aggressive treatment strategies are indicated. However, treatment related toxicity limits our ability to intensify treatment. As such, improved tools to predict tumor control and risk for toxicity would allow us to individualize treatment. For example, one could advocate escalating treatment in a patient predicted to be a poor responder with low likelihood

Conclusions

We have demonstrated an alternative feature-based approach to evaluate radiation treatment outcomes using PET and CT images in unresectable NSCLC patients. Our study demonstrates that multimodality image-feature modeling holds promise in planning individualized treatment by integrating information from multiple imaging modalities or multiple tracers if available. Combination with dosimetric variables improved performance in some cases; however, validation on larger prospective datasets is still

Conflict of Interest Statement

None.

Acknowledgements

The authors would like to thank Dr. Joseph Deasy for CERR support. This work was supported in part by the Barnes-Jewish Hospital Foundation (6661-01) and the CIHR-MOP-114910.

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