Abstract GS4-03: RAPID: A randomized trial of accelerated partial breast irradiation using 3-dimensional conformal radiotherapy (3D-CRT)
Bibliographic record
Abstract
Abstract Background Whole breast irradiation (WBI) after lumpectomy reduces the risk of local recurrence, thereby avoiding subsequent mastectomy. It is a key component of breast conserving therapy. WBI is usually given in daily fractions over 3-6 weeks. With accelerated partial breast irradiation (APBI), radiation is delivered over a week or less to the surgical cavity with a margin of normal tissue. It was introduced to provide treatment in a shorter more convenient form. 3D-CRT is an attractive approach as it is non-invasive and uses standard techniques for external beam RT that are widely available. The objective of the RAPID trial was to determine if APBI using 3D-CRT was not inferior to WBI following breast conserving surgery (BCS). Methods Women ≥40 years of age with axillary node-negative invasive ductal carcinoma, or ductal carcinoma in situ (DCIS) ≤3cm treated by BCS with clear margins of excision were eligible. Randomization was stratified for age (< or ≥50y), histology (DCIS alone or invasive breast cancer), tumor size (< or ≥1.5cm), ER status (+/-) if invasive disease, and treatment center. Patients were allocated to APBI using 3D-CRT (38.5Gy in 10 fractions delivered twice daily) or WBI (42.5Gy in 16 daily fractions or 50Gy in 25 daily fractions; boost radiation was permitted). The primary outcome was ipsilateral breast tumor recurrence (IBTR). Important secondary outcomes included radiation toxicity and nurse assessed adverse cosmesis (fair or poor on global assessment). The trial was designed to show that the 5-year IBTR rate in the APBI arm was not inferior to the WBI arm by more than 1.5% (hazard ratio [HR] ≤ 2.02) with 85% power and a one-sided alpha of 5%. Results From February 2006 to July 2011, 2135 patients from sites in Canada, Australia, and New Zealand were randomly assigned: 1070 to APBI and 1065 to WBI. The median follow-up was 8.6 years. The mean age of the study population was 61 years; 82% of patients had invasive breast cancer and 18% had DCIS only. For invasive cancers: 60% were < 1.5cm and 90% were ER positive. For DCIS tumors: 68% were < 1.5cm. A total of 65 IBTRs were observed. For the APBI patients, the 5-year and 8-year cumulative rates of IBTR were 2.3% and 3.0%, respectively. The corresponding data for the WBI patients were 1.7% and 2.8%. The HR for APBI versus WBI was 1.27, 90% confidence interval, 0.84 to 1.91. Acute radiation toxicity (occurring within 3 months of treatment start) e.g. radiation dermatitis and breast swelling was less in patients treated with APBI compared with WBI (≥ Grade 2, 28% vs 45%, p<0.001). Late radiation toxicity (beyond 3 months) e.g. breast induration and telangiectasia was greater in patients treated with APBI (≥ Grade 2, 32% vs 13%, p<0.001 and Grade 3, 4.5% vs 1.0%, p<0.001). Adverse cosmesis was higher in patients treated with APBI compared with WBI at 3 years (29% vs 17%, p<0.001) and at 5 years (32% vs 16%, p<0.001). Conclusions The APBI regimen used in our trial was non-inferior to WBI in preventing local recurrence. Although it was associated with less acute toxicity, an increase in late normal tissue toxicity and adverse cosmesis was observed with APBI. Citation Format: Whelan T, Julian J, Levine M, Berrang T, Kim D-H, Gu CS, Germain I, Nichol A, Akra M, Lavertu S, Germain F, Fyles A, Trotter T, Perera F, Balkwill S, Chafe S, McGowan T, Muanza T, Beckham W, Chua B, Olivotto I. RAPID: A randomized trial of accelerated partial breast irradiation using 3-dimensional conformal radiotherapy (3D-CRT) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr GS4-03.
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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 | 0.003 | 0.002 |
| Meta-epidemiology (narrow) | 0.003 | 0.001 |
| Meta-epidemiology (broad) | 0.004 | 0.002 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.000 | 0.002 |
| Scholarly communication | 0.002 | 0.001 |
| Open science | 0.002 | 0.001 |
| Research integrity | 0.002 | 0.003 |
| Insufficient payload (model declined to judge) | 0.019 | 0.002 |
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".