Connie Y. Chang MD, Presenter: Nothing to Disclose

Pari Pandharipande MD, Abstract Co-Author: Nothing to Disclose

Mukesh Gobind Harisinghani MD, Abstract Co-Author: Nothing to Disclose

G. Scott Gazelle MD, MPD, PhD, Abstract Co-Author: I was paid to teach a course at Philips Electronics in January 2009

To identify mesorectal lymph node size criteria for triage to preoperative chemoradiation that optimize key patient outcomes in T2 rectal cancer.

We developed a decision-analytic model to predict outcomes for patients with T2 rectal cancer at MRI. We considered five strategies for assignment of preoperative chemoradiation: (1) treat patients with any node >3mm; (2) >5mm; (3) >7mm; (4) treat all patients; and (5) treat no patients. T2N1 prevalence and sensitivity and specificity for each size threshold were derived from the literature. If malignant nodes were missed by the size criteria used, patients received postoperative chemoradiation, which had greater morbidity than preoperative chemoradiation. The percentages of patients that experienced local recurrence and acute and long-term radiation toxicity were computed for each threshold. Sensitivity analysis was performed to assess effects of uncertainty in model estimates upon results.

The 5-year probability of local recurrence was lowest when all patients were treated preoperatively (4.6%). Long-term radiation toxicity was minimized by restricting preoperative chemoradiation to patients with nodes >7mm; 5.6% of patients were affected using this threshold. Acute radiation toxicity was minimized by treating no patients preoperatively; 10% of patients were affected (from postoperative chemoradiation) using this threshold. At the 7mm threshold, the local recurrence probability was 0.8% higher than when all patients were treated preoperatively, and the acute radiation toxicity rate was 0.1% higher than when none were treated preoperatively. Results were most sensitive to T2N1 prevalence, and to the sensitivity and specificity for each threshold.

Selection of mesorectal lymph node size criteria for triage to preoperative chemoradiation in T2 rectal cancer is linked to the relative prioritization of key patient outcomes. Restriction of preoperative chemoradiation to patients with any node >7mm will minimize long-term radiation toxicity, and may best balance risks of acute radiation toxicity and local recurrence.

The lymph node size threshold to triage to preoperative chemoradiation in T2 rectal cancer varies based on the clinical outcome prioritized.A 7 mm threshold may optimizie outcomes for many patients.

Chang, C, Pandharipande, P, Harisinghani, M, Gazelle, G, Optimizing Triage to Preoperative Chemoradiation in T2 Rectal Cancer Based on Mesorectal Lymph Node Size: A Decision Analysis Informed by Patient Outcomes.  Radiological Society of North America 2008 Scientific Assembly and Annual Meeting, February 18 - February 20, 2008 ,Chicago IL. http://archive.rsna.org/2008/6017086.html