Tumour volume changes assessed with high-quality KVCT in lung cancer patients undergoing concurrent chemoradiotherapy

Abstract

Objective: We evaluated tumour volume changes in patients with lung cancer undergoing concurrent chemoradiotherapy using image-guided radiotherapy (RT). Methods: The kilovoltage image was obtained using CT on rail at every five fractions. The gross tumour volumes (GTVs), including the primary tumour and lymph nodes (LNs), were contoured to analyse the time and degree of tumour regression. Results: 46 patients [32, non-small-cell lung cancer (NSCLC), and 14, small-cell lung cancer (SCLC)] were included in this study. In total, 281 CT scans and 82 sites of GTVs were evaluated. Significant volume changes occurred in both the NSCLC and SCLC groups (p , 0.001 and 0.002), and the average GTV change compared with baseline was 49.85 6 3.65 [standard error (SE)]% and 65.95 6 4.60 (SE)% for the NSCLC and SCLC groups, respectively. A significant difference in the degree of volume reduction between the primary tumour and LNs was observed in only the NSCLC group (p , 0.0001) but not in the SCLC group (p 5 0.735). The greatest volume regression compared with the volume before the five fractions occurred between the 15 and 20 fractions in the NSCLC group and between the 5 and 10 fractions in the SCLC group. Conclusion: Both primary tumour and LNs were well defined using CT on rail. Significant volume changes occurred during RT, and there was a difference in volume reduction between the NSCLC and SCLC groups, regarding the degree and timing of the tumour reduction in the primary tumour and LNs. Advances in knowledge: NSCLC and SCLC groups showed differences in the degree and timing of volume reduction. The primary tumour and LNs in NSCLC regressed differently.Lung cancer is the most common cause of cancer mortality in the Republic of Korea, accounting for 22.2% all cancer deaths. Although the survival rate continues to increase, the prognosis remains poor with a 5-year relative survival rate of 20.7% in patients diagnosed from 2007 to 2011. 1 Multimodality treatment, including radiotherapy (RT), is a mainstay in the treatment of locally advanced non-smallcell lung cancer (NSCLC) and limited-stage small-cell lung cancer (SCLC) because it improves local control and overall survival. [2][3][4][5] Several recent studies have shown that an increasing radiation dose resulted in the improvement of local control and overall survival.6-9 Currently, Phase III randomized studies are under way to determine the optimal dose and fractionation schedule. Radiation oesophagitis and pneumonitis are major complications that limit the potential for dose escalation. Changes in tumour volume, patients' weight, pulmonary atelectasis and pleural effusions were noted during RT and modification of the treatment plan may be required over the course of the treatment. Adaptive planning can reduce the radiation exposure of an organ at risk (such as normal lung and oesophagus) and may improve local control.Several studies have reported that tumour shrinkage occurs during RT using the various image-guided RT modalities, such as electronic portal imaging, mega...

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