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Patterns of care and outcomes for adjuvant treatment of pT3N0 rectal cancer using the National Cancer Database.

Background
The standard of care in locally advanced rectal cancer is preoperative chemoradiation followed by surgical resection. However, the optimal treatment paradigm is currently controversial for patients with pathological T3N0 (pT3N0) in the era of total mesorectal excision (TME). Given the paucity of data, we conducted an analysis using the National Cancer Database (NCDB) to identify patterns of care and outcomes.


Methods
We utilized the NCDB to identify 7,836 non-metastatic, pT3N0 rectal cancer patients who did not receive neoadjuvant therapy from 2004-2014. Univariate and multivariable analysis for factors affecting treatment selection were completed using logistic regression. Overall survival (OS) analyses were completed using Cox regression modeling, incorporating propensity scores with inverse probability of treatment weighting (IPTW) and conditional landmark analysis.


Results
There was a significant improvement in OS in patients receiving adjuvant chemotherapy (P<0.01) or radiotherapy (RT) with chemotherapy (P<0.01) vs. observation alone. There was no significant difference between RT vs. observation (P=0.54) and chemotherapy vs. chemotherapy with RT cohorts (P=0.15). Multivariable analysis showed age, gender, race, insurance status, income, Charlson-Deyo Comorbidity Condition (CDCC) score, facility location, grade, surgical margin, RT, and chemotherapy to be statistically significant predictors of OS. After correcting for indication and immortal time biases, chemotherapy, with or without RT, improved OS compared with observation [hazard ratio (HR) 0.48, P<0.001]. This benefit was maintained in the margin negative cohort.


Conclusions
Practice patterns vary in the management of pT3N0 rectal cancer patients. This analysis suggests that the use of adjuvant therapy, particularly adjuvant chemotherapy with or without RT, appears to improve OS.