Conformal Preoperative Endorectal Brachytherapy Treatment for Locally Advanced Rectal Cancer
Bibliographic record
Abstract
PURPOSE: Downstaging rectal carcinoma by preoperative radiotherapy decreases local recurrence, and recent phase II studies suggest that, in the lower one-third lesions, sphincter-preserving surgery can be considered. The purpose of the current study was to assess the efficacy and the toxicity of endorectal high dose-rate brachytherapy as a preoperative downstaging treatment modality. METHODS: Patients with newly diagnosed invasive rectal adenocarcinoma, T2 to very early T4, operable tumors were eligible. A dose of 26 Gy was given over four consecutive daily treatments of 6.5 Gy prescribed at the tumor radial margin using endorectal brachytherapy with high dose-rate delivery system. Surgery as planned initially was done four to eight weeks later to allow for tumor downstaging. Patients found to have pathologic positive nodes received postoperative external beam (45 Gy/25 fractions) to the pelvis and systemic 5-fluorouracil-leucovorin chemotherapy. RESULTS: Forty-nine patients entered the study. Tumors were in the lower one-third in 24 patients, middle one-third in 22, and upper one-third in 3. With preoperative endorectal ultrasound and magnetic resonance imaging, the clinical staging of the tumors was: 3 T2, 42 T3, 4 T4, and 16 N1-2. Acute toxicity related to brachytherapy was limited to a moderate proctitis (Radiation Therapy Oncology Group acute toxicity scoring system, Grade 2) in all patients, with two patients with tumors extending into the anal canal having Grade 3 dermatitis. Forty-seven patients underwent surgery. Two patients refused their operation based on a normal endoscopic rectal ultrasound after treatment. A complete clinical response was obtained in 32 of 47 (68 percent) patients with 32 percent pathologically pT0N0-1, and 36 percent had only residual microfoci of carcinoma. The surgical approaches did not yield more complications than expected. CONCLUSION: Preoperative high dose-rate endorectal brachytherapy seems to be safe, because acute toxicity was mainly local, with moderate proctitis (Grade 2) and occasional dermatitis (Grade 3) for very low tumors. Finally, this modality, by providing high rate of tumor downstaging and downsizing especially for patients with lesions in the lower one-third of the rectum, represents a definite potential for sphincter-preserving surgery for investigation in future studies.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.001 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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 teacher head, 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".