13.10 Incomplete Neoadjuvant Radiotherapy Is Associated With Inferior Survival For Rectal Cancer Patients

Posted on January 18, 2016

Z. Sun1, M. A. Adam1, J. Kim1, M. Palta2, B. G. Czito2, J. Migaly1, C. R. Mantyh1 1Duke University Medical Center,Surgery,Durham, NC, USA 2Duke University Medical Center,Radiation Oncology,Durham, NC, USA

Introduction:
While failing to complete chemotherapy has been shown to adversely affect survival in colorectal patients, the effect of incomplete neoadjuvant radiotherapy dosing is unclear.

Methods:
Adults with stage II-III rectal adenocarcinoma from the 2006-2012 National Cancer Data Base who received neoadjuvant chemoradiation followed by surgical resections were included. Multivariable regression methods were used to compare resection margin positivity, permanent colostomy rate, 30-day readmission, 90-day mortality, and overall survival between patients who received complete (45-50.4 Gy) and incomplete (<45 Gy) doses of radiation preoperatively.

Results:
Among 18,060 patients included, 971 (5%) received incomplete doses of neoadjuvant radiation. Median radiation dose received among those who did not achieve complete dosing was 36 Gy (Interquartile range 19.8-41.4 Gy). Female sex (OR 0.70, p<0.001) and receiving radiation at a different hospital (OR 0.71, p<0.001) were independent predictors of failing to achieve complete dosing, while private insurance status was predictive of success (OR 1.54, p= 0.003). At 5-years follow up, overall survival was improved among patients who received complete radiotherapy (73% vs. 63%, p<0.001). After adjustment for demographic, clinical, and tumor characteristics, patients receiving complete versus incomplete radiotherapy dose had similar resection margin positivity, permanent colostomy rate, 30-day readmission, and 90-day mortality (all p>0.05). However, complete radiation dose had significantly lower risk of long-term mortality (HR 0.70, p<0.001).

Conclusion:
Achieving target radiation dose of 45-50.4 Gy is associated with survival benefit in patients with locally advanced rectal cancer. Regionalization of multimodality oncology care may increase probability of completing neoadjuvant therapy.