Favorable Pathologic and Long-Term Outcomes From the Conventional Approach to Abdominoperineal Resection
Bibliographic record
Abstract
BACKGROUND: Suboptimal oncologic outcomes from abdominoperineal resection have been related to high rates of circumferential margin involvement. The extralevator approach has gained popularity as a means of reducing circumferential margin involvement, but it remains unknown whether comparable outcomes are achievable with a conventional approach to abdominoperineal resection. OBJECTIVE: This study aimed to determine the rate of circumferential margin involvement, to identify factors predictive for a positive circumferential margin, and to relate these findings to long-term outcomes. DESIGN: This is a retrospective analysis of a prospective clinical database. SETTINGS: This study was conducted at a single center, Mount Sinai Hospital, Toronto. PATIENTS: Patients were included who underwent abdominoperineal resection for low rectal adenocarcinoma between 1997 and 2006. MAIN OUTCOME MEASURES: The main outcome measures included the rate of circumferential margin involvement, local recurrence, and disease-free survival. RESULTS: A total of 115 patients underwent abdominoperineal resection for primary adenocarcinoma of the rectum. A positive circumferential margin was demonstrated in 18 patients (15.7%). Intraoperative perforations occurred in 7 patients (6.1%). Tumors located anteriorly had a higher rate of circumferential margin involvement (31.6%) compared with lateral (13%), posterior (10%), and circumferential tumors (0%) (P = .024). This finding was reflected by a reduced median distance to the circumferential margin in anterior tumors. Curative resections (n = 108) were followed up for a median of 55.5 months. The 5-year local recurrence rate was 10.6% and the 5-year disease-free survival was 67.4%. Cox regression analysis revealed that circumferential margin involvement was an independent predictor for local recurrence; and T-category, N-category, and circumferential margin involvement for disease-free survival. LIMITATIONS: This study was limited by its sample size and the number of outcome events. CONCLUSIONS: The conventional approach to abdominoperineal resection can produce oncologic outcomes comparable to the extralevator approach. However, the rate of circumferential margin involvement is higher than in restorative procedures and may be related to difficulties in obtaining adequate clearance in anterior tumors.
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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 | 0.000 | 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 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".