The Relationship between Primary Gross Tumor Volume and Tumor Response of Locally Advanced Rectal Cancer: pGTV as a More Accurate Tumor Size Indicator

Abstract

Purpose: To identify the clinical predictive factors of tumor response and to evaluate the significance of primary gross tumor volume (pGTV), obtained from radiotherapy planning, in predicting tumor response. Materials and Methods: We retrospectively analyzed data of consecutive locally advanced rectal cancer (LARC) patients who were treated with neoadjuvant chemoradiotherapy (nCRT) followed by radical surgery at our institution between March 2009 and December 2017. We identify independent predictors of tumor response to nCRT by statistical analysis. Disease-free survival (DFS) starting from the time of surgery was calculated by the Kaplan–Meier method, and log-rank tests were performed to compare DFS between patients with superior and inferior tumor response. Results: Overall, 185 LARC patients received nCRT, of whom 89 (48.11%) achieved superior tumor response. Diminutive pGTV (p = 0.038) and distance from the anal verge (DAV) (p = 0.006) were independent predictive factors of superior tumor response. Meanwhile, pGTV can be regarded as an independent predictor of pathologic complete response (pCR) (p = 0.036). The log-rank test revealed that DFS was longer in the diminutive pGTV group than in the giant pGTV group (p = 0.001). Conclusions: pGTV, as a measure of tumor size, is not only an important prognostic indicator but also an independent predictive factor of tumor response, even pCR.

Keywords:

• primary gross tumor volume
• tumor response
• neoadjuvant chemoradiotherapy
• locally advanced rectal cancer
• tumor regression grade

This article is referred to by:

Primary Gross Tumor Volume (pGTV) and Tumor Response in Locally Advanced Rectal Cancer (LARC). Is There Any Correlation?

Acknowledgments

The authors would like to thank the medical physicists Wen Chen and Xiaoyu Yang for their help with editing of the radiotherapy planning images.

Author contribution

Yuqiang Li, Qian Pei, Haiping Pei, and Hong Zhu conceived and designed the study. Yuqiang Li and Wenxue Liu wrote the article. Xiangping Song and Qian Pei assessed the tumor response. Wenxue Liu, Qian Pei, and Yuqiang Li collected and analyzed the datas.

Declaration of Interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.

Ethical approval and consent to participate

This retrospective study was approved by Medical Ethics Committee of Xiangya Hospital, Central South University with the Approval No. 2018071018. All participants signed written informed consent for their participation in this study.

Additional information

Funding

This work was funded by Contract grant sponsor: The Nature Scientific Foundation of China; Contract grant number: 81702956; Contract grant sponsor: The Strategy-Oriented Special Project of Central South University in China; Contract grant number: ZLXD2017003; The XiangYa-Peking University Wei Ming Clinical and Rehabilitation Research Fund; Contract grant number: xywm2015I21.