Abstract P4-12-24: Evaluation of partial breast irradiation suitability in early stage breast cancer patients
Bibliographic record
Abstract
Abstract Purpose: Partial Breast Irradiation (PBI) treats the tumor bed plus a margin in low risk early stage breast cancers, reducing exposure to organs at risk. Randomized trials have shown that PBI with external beam radiotherapy is non-inferior to whole breast irradiation in terms of local control with fewer late normal tissue adverse events. We aimed to determine the proportion of women with early stage breast cancer suitable for external beam PBI at our institution using adapted ASTRO guidelines for accelerated PBI whereby both clinical-pathological factors and visualization of the tumor bed/cavity on planning scans were determined to quantify PBI eligibility. Methods: Patients were identified retrospectively from January 1, 2013 to November 1, 2018 based on age (≥55), tumor size (≤2cm invasive, ≤2.5cm DCIS), nodal negativity and grade (1 or 2). Cases identified were unifocal, lymphovascular invasion negative, ER positive, HER2 negative, with margins ≥2mm (invasive) and ≥3mm (DCIS), no chemotherapy, non-lobular, no extensive intraductal component, no previous/ bilateral cancers and endocrine therapy optional. Planning scans were reviewed to assess for presence of surgical clips and assigned cavity visualization scores (CVS); CVS 1=cavity not visualized, CVS 2=cavity visualized with indistinct margins, CVS 3=cavity visualised with some distinct margins and heterogeneous appearance, CVS 4= cavity visualised with mostly distinct margins and mildly heterogeneous appearance, CVS 5= all cavity margins clearly defined and homogeneous appearance. These features were used to determine if cases were considered radiologically suitable for PBI. Results: Thirty-seven percent (1051/2824) of cases identified were deemed eligible based on age, grade and T1N0/Tis. Of the 1051, 306 (29%) met all the pathologic criteria; the main reasons for exclusion were previous breast cancer, lobular histology, or multifocality. Median age of eligible cases was 65 years (range 55-88 years). The majority (254) had invasive disease (T1mi: 6, T1a: 17, T1b: 98, T1c: 133); 52 had DCIS. There were 169 right-sided and 137 left-sided cases. Endocrine therapy was documented in 55% of cases. CVS (1-5) were: 11%, 22%, 30%, 29%, 8%. Overall, 66% (201/306) of cases were considered radiologically suitable for PBI (of the 201 cases, 97% had CVS ≥3). Seventy-two cases (72/306; 24%) had tumor bed clips, of which, 34 were considered suitable for PBI (91% CVS ≥3; 9% CVS 2). Conclusions: Overall, a low proportion of all patients were eligible for PBI based on clinical features, but two-thirds of eligible cases were suitable for PBI based on CVS score alone. In contrast, the suitability for PBI within the cohort with surgical clip placement was low. Visualization of the tumor bed is essential to safely deliver PBI and is guided by identification of the cavity seroma and/or surgical clips. Development of standard practice guidelines for surgical clip positioning to identify the tumor bed will potentially assist in increasing the proportion of early stage breast cancer patients suitable to receive PBI, even if the CVS is less favorable. Citation Format: Christine Anne Koch, Gemma Corey, Kathy Han, Grace Lee, Tom Purdie, Chris McIntosh, Patricia Lindsay, Fei-Fei Liu, Anthony Fyles, Wilf Levin, Jennifer Croke, Aisling Barry, Danielle Rodin, Nhu Tram Nguyen, Tatiana Conrad. Evaluation of partial breast irradiation suitability in early stage breast cancer patients [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P4-12-24.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.003 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.004 | 0.001 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".