Rectal Cancer Survival for Residual Carcinoma In Situ Vs. Pathologic Complete Response After Neoadjuvant Therapy.

BACKGROUND: Pathologic complete response after neoadjuvant chemoradiotherapy for rectal cancer is associated with improved survival. It is unclear whether residual carcinoma in situ portends a similar outcome.

OBJECTIVE: To compare survival of patients with locally advanced rectal cancer who received neoadjuvant therapy and achieved pathologic carcinoma in situ versus pathologic complete response.

DESIGN: Retrospective cohort study.

SETTING: National public database.

PATIENTS: A total of 4,594 patients in the National Cancer Database from 2006 to 2016 with locally advanced rectal cancer who received neoadjuvant therapy, underwent surgery, and had node-negative, ypTis or ypT0 on final pathology were included. 4,321 (94.1%) had ypT0 and 273 (5.9%) had ypTis on final pathology.

MAIN OUTCOME MEASURES: Overall survival.

RESULTS: Median age was 60 years. 1,822 patients (39.7%) were female. 54.5% (n = 2,503) had stage II disease and 45.5% (n = 2,091) had stage III disease on initial staging. The ypTis group had decreased overall survival compared to the ypT0 group (HR 1.42, 95% CI 1.04-1.95, p = 0.028). Other factors associated with decreased overall survival were an older age at diagnosis, increasing Charlson-Deyo score, and poorly differentiated tumor grade. Variables associated with improved survival were female sex, private insurance, and receipt of both neoadjuvant and adjuvant chemotherapy. For the total cohort, there was no difference in survival between clinical stage 2 versus stage 3.

LIMITATIONS: Standard therapy versus total neoadjuvant therapy were unable to be abstracted. Overall survival was defined as time from surgery to death from any cause or last contact, allowing for some erroneously misclassified deaths.

CONCLUSIONS: ypTis is associated with worse overall survival than ypT0 for locally advanced rectal cancer patients who receive neoadjuvant chemoradiotherapy followed by surgery. For this cohort, clinical stage was not a significant predictor of survival. Prospective trials comparing survival for these pathologic outcomes are needed. See Video Abstract.