Plan quality assessment of modern radiotherapy delivery techniques in left-sided breast cancer: an analysis stratified by target delineation guidelines.

Irfan Ahmad,Ram Bajpai,Alexis Andrew Miller,Rahul Lal Chowdhary,Chandi Prasad Bhatt,Anjali Kakria Pahuja,Kundan Singh Chufal,Munish Gairola,Akanksha Chhabra

doi:10.1259/bjro.20200007

Abstract

Objective:This study compares planning techniques stratified by consensus delineation guidelines in patients undergoing whole-breast radiotherapy based on an objective plan quality assessment scale.Methods:10 patients with left-sided breast cancer were randomly selected, and target delineation for intact breast was performed using Tangent (RTOG 0413), ESTRO, and RTOG guidelines. Consensus Plan Quality Metric (PQM) scoring was defined and communicated to the physicist before commencing treatment planning. Field-in-field IMRT (FiF), inverse IMRT (IMRT) and volumetric modulated arc therapy (VMAT) plans were created for each delineation. Statistical analyses utilised a two-way repeated measures analysis of variance, after applying a Bonferroni correction.Results:Total PQM score of plans for Tangent and ESTRO were comparable for FiF and IMRT techniques (FiF vs IMRT for Tangent, p = 0.637; FiF vs IMRT for ESTRO, p = 0.304), and were also significantly higher compared to VMAT. Total PQM score of plans for RTOG revealed that IMRT planning achieved a significantly higher score compared to both FiF and VMAT (IMRT vs FiF, p < 0.001; IMRT vs VMAT, p < 0.001).Conclusions:Total PQM scores were equivalent for FiF and IMRT for both Tangent and ESTRO delineations, whereas IMRT was best suited for RTOG delineation.Advances in knowledge:FiF and IMRT planning techniques are best suited for ESTRO or Tangent delineations. IMRT also yields better results with RTOG delineation.

Highlights

Breast irradiation is essential in the management of breast cancer after breast-c onserving surgery (BCS) and contemporary delivery techniques rely on consensus delineation guidelines to reduce long-term cardiac morbidity, especially in left-sided breast cancer.[1,2,3,4]One of the most widely used delineation guideline is the RTOG 0413 WBI (Tangent) Protocol, which includes all clinically palpable breast tissue in its tangential design.[5]
The European SocieTy of Radiation Therapy (ESTRO) Consensus Guideline (Figure 2A) For plans based on the ESTRO guideline, the combined PQM scores for each planning technique demonstrated that Field-in-Field Intensity Modulated Radiotherapy Technique (FiF) was comparable to Intensity Modulated Radiotherapy Technique (IMRT) (FiF vs IMRT, p = 0.304) and that both achieved higher scores than Volumetric Modulated Arc Therapy (VMAT) (FiF vs VMAT, p < 0.001; IMRT vs VMAT, p < 0.001)
Individual subscores for left lung, heart, and right breast were lower for VMAT compared to both FiF and IMRT

Summary

Introduction

One of the most widely used delineation guideline is the RTOG 0413 WBI (Tangent) Protocol, which includes all clinically palpable breast tissue in its tangential design.[5] The adoption of CT-based radiotherapy planning and the lack of an anatomical basis in this guideline drove the development of two consensus guidelines: the RTOG (Radiation Therapy Oncology Group) and the European SocieTy of Radiation Therapy (ESTRO) consensus guidelines.[3,4]. The RTOG consensus guideline provides anatomical bony and muscular landmarks for clinical target volume (CTV) delineation.[3,5] In contrast, the ESTRO consensus guideline provides vessel-b ased landmarks to define the medial and lateral extent of the breast tissue, and recommends a ventral retraction of caudal CTV to distinguish abdominal fat from mammary fat.[4] Both RTOG and ESTRO consensus guidelines recommend adding a planning target volume (PTV) margin to the delineated CTV, in contrast to the RTOG 0413 WBI (Tangent) target which is delineated directly as a PTV.[3,4,5]

Methods

Results

Conclusion