160: Limiting Chest Wall Toxicity by Adapting the Dose Schedule and Dose Constraints in SBRT for Early-Stage Lung Cancer
Bibliographic record
Abstract
Purpose: Despite improved staging and operative techniques, rate of incomplete resection (R1) of NSCLC has remained significant over the last decades.Patients with R1 resection have significantly worse survival compared to those with complete resection (R0).SBRT delivers high dose radiotherapy (RT) to tumours, in a short time (1-10 treatments), with high precision while sparing normal organs.The efficacy of SBRT in treating small lung tumours is documented but its use as neo-adjuvant therapy in LA-NSCLC is not reported yet.We hypothesized that a short course of pre-operative SBRT can be done safely and could improve rates of R0 resection of LA-NSCLC and conducted a Phase I trial (LINNEARRE I) to investigate the safety and feasibility of delivering, timely, neo-adjuvant SBRT in operable patients with LA-NSCLC at risk for positive resection margins.Methods and Materials: Twenty appropriately staged (PET-CT/MRI and mediastinal staging) patients with biopsy proven T3-T4, N0-1, M0 NSCLC will be enrolled.Patients would be deemed medically operable by the surgical team but at risk of < R0 resection (due to invasion of mediastinal or hilar structures, chest wall or vertebral bodies).Primary outcome is feasibility i.e. the ability to complete SBRT as planned and proceed to surgery (Sx) within six weeks.Secondary outcomes include acute and late adverse events, R0/R1/R2 rates and secondary surrogates of feasibility.SBRT is delivered in over two weeks (in 10 fractions).Dose is escalated from 35 Gy to 50 Gy.Five patients will be accrued to each dose level of 35, 40, 45 and 50 Gy.At the latter dose level, normal tissue (nt) BED (133 Gy) exceeds that delivered concurrently with chemotherapy with 63-66 Gy/30 fractions (107-110 Gy) but is similar to that delivered by recent dose-escalation chemo-RT (74 Gy) studies.Clinical target volume (CTV) includes only the area of tumour deemed at risk of incomplete resection expanded by 3-5 mm into surrounding tissues where there is clinical suspicion of invasion.Results: This study opened to accrual in late 2015.Dosimetric feasibility was tested in virtual plans of selected eligible cases that were planned to receive treatment at the highest planned dose level (50 Gy).All cases met dosimetric constraints for planned target volume (PTV) and organs at risk (OAR: great vessels, heart, esophagus, and proximal bronchi).Examples of virtual plans will be illustrated.Conclusions: This is the first study to investigate SBRT as a neoadjuvant therapy in LA-NSCLC.Virtual plans suggest that is feasible to deliver neoadjuvant SBRT safely to tumour volumes at risk for positive margins.A key aims of this study is to examine the adaptation of workflow in a Canadian academic institution to achieve timely neoadjuvant SBRT delivery.If successful this Phase I study will lead to further evaluation of pre-operative SBRT in LA-NSCLC, to help achieve improved rates of complete resection and improved outcomes.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.002 | 0.000 |
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".