Predictors of primary and distant site surgery in patients with stage IV colorectal cancer.

499 Background: Operative management of primary tumor and distant metastases in stage IV colorectal cancer is highly variable and removal of asymptomatic primary tumors in the setting of distant disease remains controversial. The purpose of our study was to describe the patterns of surgery in stage IV colorectal cancer patients in a US population-based cohort and explore patient and tumor characteristics associated with treatment selection and survival. Methods: Stage IV colorectal cancer patients in Los Angeles County from 2000 to 2006 were identified using the LA County Cancer Surveillance Program registry. The cohort included 2,956 patients (2,211 stage IV colon and 745 stage IV rectal cancers). Cox proportional hazard models were used to estimate survival. Treatment was categorized as primary surgery, distant site surgery, or chemotherapy only. Multivariate logistic regression was used to identify patient and tumor variables associated with treatment. Results: Greater than 65% of the stage IV colorectal cohort had primary tumor surgery of which 51% had chemotherapy. Only 4.5% had surgery to remove distant disease. Patients who had chemotherapy only and no surgery was 15%. Median survival of primary surgery, distant surgery, or chemo only was 14, 21, and 11 months. Multivariate Cox regression revealed that primary surgery and distant surgery had a decreased risk of death compared to no surgery (HR= 0.4 p<.0001, HR=0.7 p<.004). Multivariate logistic regression was used to identify predictors associated with treatment selection. Patients >65 years (p<.003); low socioeconomic status (p<0.05); and rectal tumors (p<.0001) were less likely to have surgery of the primary tumor. Female gender (p<.0001) and primary tumor surgery (p<.0001) were predictors for distant site surgery whereas age>65 years (p<.0001) had a negative association. Conclusions: Our population-based study of stage IV colorectal cancer patients suggests that the majority of stage IV patients with distant disease have surgery, but less than 5% have surgery for distant disease. Although survival of stage IV colorectal patients is improved with surgery, increasing age, low socioeconomic status, and rectal tumors are negative predictors for undergoing surgery.