{'fraction_non_alphanumeric': 0.03477112676056338, 'fraction_numerical': 0.022887323943661973, 'mean_word_length': 5.384831460674158, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Feasibility of a randomized trial of extended lymphadenectomy for pancreatic cancer.

HYPOTHESIS
The required sample size of a prospective randomized trial comparing standard pancreaticoduodenectomy with pancreaticoduodenectomy plus extended lymphadenectomy for pancreatic adenocarcinoma is prohibitively large, making such a trial infeasible.


DESIGN
Retrospective cohort study.


SETTING
Comprehensive cancer center.


PATIENTS
We identified 158 patients who underwent pancreaticoduodenectomy for pancreatic adenocarcinoma with separate pathologic analysis of second-echelon lymph nodes, defined as lymph nodes along the proximal hepatic artery and/or the great vessels.


MAIN OUTCOME MEASURES
To estimate the sample size required for a randomized trial, we devised a biostatistical model with the following assumptions: extended lymphadenectomy can benefit only patients who (1) actually have disease removed from second-echelon nodes, (2) have microscopically negative (R0) primary tumor resection margins, and (3) do not have visceral metastatic (M0) disease.


RESULTS
Seventy-six patients (48.1%) had negative first- and second-echelon lymph nodes, 65 (41.1%) had positive first-echelon and negative second-echelon lymph nodes, and 17 (10.8%) had positive first- and second-echelon lymph nodes. Patients with positive second-echelon lymph nodes had an R0 resection rate of 47.1%. At a median follow-up of 65.1 months, 4 patients with positive second-echelon lymph nodes were alive, but 3 had recurrent disease. This implies that only 1 patient (5.9%) with positive second-echelon lymph nodes may have had true M0 disease. Therefore, only 0.3% of patients (10.8% with positive second-echelon lymph nodes x 47.1% with R0 resection x 5.9% with M0 disease) may achieve a survival benefit from extended lymphadenectomy. A randomized trial of standard pancreaticoduodenectomy vs pancreaticoduodenectomy with extended lymphadenectomy would require 202 000 patients in each study arm to detect such a small difference.


CONCLUSIONS
Definitive evaluation of the potential benefits of extended lymphadenectomy would require a prohibitively large sample size. Adequately powered randomized trials to address the potential benefit of extended lymphadenectomy are infeasible.