The dosimetric impact of target volume delineation variation for cervical cancer radiotherapy

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• 作者：Gemma Eminowicz ; Vasilis Rompokos ; Christopher Stacey ; Mary McCormack
• 关键词：Cervical cancer radiotherapy ; Inter-observer variation ; Dosimetry
• 刊名：Radiotherapy and Oncology
• 出版年：2016
• 出版时间：September 2016
• 年：2016
• 卷：120
• 期：3
• 页码：493-499
• 全文大小：2393 K

文摘

Cervical cancer inter-observer delineation variation has been demonstrated. This article addresses its dosimetric impact.

Methods

21 centres outlined two INTERLACE trial quality assurance test cases. A gold standard clinical target volume (GSCTV) was created from a consensus and STAPLE outline. RapidArc plans were created for all centres’ planning target volumes (PTVs; PTV1 + 2). Gold standard PTVs (GSPTVs) were created for each plan by applying each centre’s CTV–PTV margins to GSCTV. DVH parameters including D95% and Dmean for each PTV1 + 2 and GSPTV were compared, representing planned versus GSPTV delivered dose. PTV1 + 2 and GSPTV V95% was also calculated.

Results

Reviewing all parameters, no plans achieved acceptable GSPTV coverage. GSPTV V95% ⩾ 95% was not achieved for any plan. GSPTV V95% < 90% in 15/21 (case 1) and 14/22 (case 2) and <80% in 2 plans from both cases. GSPTV V95% is on average 10–15% lower than planned and GSPTV D95% is 10–20% lower than planned. Most common GSCTV anatomical areas not receiving 95% dose were vagina, obturator and external iliac nodes and, in case 1, the superior nodal aspect.

Conclusion

Cervical cancer CTV delineation variation leads to significant reductions in dose delivered to GSPTV. This highlights the ongoing importance of standardising delineation in the IMRT era.