Clinical Report: Evaluation of Observer Agreement in Target Volume Definition

Overview

This study quantifies inter-observer discrepancies in clinical target volume (CTV) delineation among radiation oncologists following breast-conserving surgery and mastectomy.

Background

Accurate CTV delineation is crucial in breast cancer radiotherapy to ensure effective treatment while minimizing exposure to surrounding organs at risk. Despite advancements in automated contouring techniques, manual delineation remains the standard, particularly in community settings where variability may be pronounced.

Data Highlights

Key Findings

• Inter-observer variability in CTV delineation was assessed among 22 radiation oncologists.
• Large volumes showed acceptable consistency with DSC means of 0.80 for CTVp_breast.
• Moderate consistency was observed for supraclavicular volumes (CTVn_L4 DSC mean: 0.57).
• Poor consistency was noted for axillary Level III (CTVn_L3 DSC mean: 0.38).

Clinical Implications

The findings indicate that while large target volumes can be delineated with reasonable consistency, significant variability exists for regional nodal stations.

Conclusion

The study highlights variability in CTV delineation practices in breast cancer radiotherapy.

Related Resources & Content

1. Author(s)/Org, Source, Year -- Title
2. Frontiers in Oncology, 2026 -- Glandular tissue–based versus anatomical landmark–based CTV delineation in postoperative breast cancer radiotherapy: a dosimetric comparison
3. Evaluation of Aesthetic Results and Symmetry in Patients Receiving Bilateral Therapeutic Mammoplasty for Breast Cancer, 2020
4. The ASCO Post, 2014 -- Margin Reassessment in Breast-Conservation Therapy
5. Postmastectomy Radiation Therapy: An ASTRO-ASCO-SSO Clinical Practice Guideline | Journal of Clinical Oncology
6. Partial Breast Irradiation for Patients With Early-Stage Invasive Breast Cancer or Ductal Carcinoma In Situ: An ASTRO Clinical Practice Guideline - ScienceDirect
7. Twenty‐year results of the randomized European Organization for Research and Treatment of Cancer trial 22922/10925 evaluating internal mammary chain and medial supraclavicular lymph node irradiation in stage I–III breast cancer - PMC
8. Postmastectomy Radiation Therapy: An ASTRO-ASCO-SSO Clinical Practice Guideline | Journal of Clinical Oncology
9. Partial Breast Irradiation for Patients With Early-Stage Invasive Breast Cancer or Ductal Carcinoma In Situ: An ASTRO Clinical Practice Guideline - ScienceDirect
10. Twenty‐year results of the randomized European Organization for Research and Treatment of Cancer trial 22922/10925 evaluating internal mammary chain and medial supraclavicular lymph node irradiation in stage I–III breast cancer - PMC