Session Item

For T3/T4N0 or T(any)N+ or locally unresectable rectal cancer, preoperative chemoradiation (pre-OP CRT) followed by radical resection is the standard of care. Tumor regression grade reflects the response of a tumor to neoadjuvant treatment and is the main reason behind the development of novel surgical strategies for managing patients, classified as good responders to neoadjuvant treatment. The purpose of this study is to evaluate the potential predictive factors for pathologic good response.

From January 2010 to December 2018, 98 patients with primary rectal cancer (without distant metastases) finished preoperative CRT, followed by radical surgery at our institution. Patients’ demographic characteristics, clinical and pathological variables, and laboratory data at baseline, during-CCRT and peri-operative, were collected by review of medical records. We divided patients into two groups, based on the AJCC tumor regression grade, by pathological finding: good responders, TRG 0-1; poor responders, TRG 2-3. Kaplan-Meier curve analysis was used to assess overall survival (OS) and progression-free survival (PFS). Logistic regression (LR) was used to evaluate those variables associated with response.

The median age was 58 years old, male predominant (72.4%) and most (89.8%) with moderately differentiated histology. 19.4% of all patients were T2 stage (n =19), 73.5% were T3 stage (n = 72) and 7.1% were T4 stage (n=7). The median initial CEA concentration was 4.7 ng/dL.

All patients completed CRT either with 50Gy in 25 fractions or with 50.4Gy in 28 fractions, to whole pelvis and pelvic lymph nodes. The neoadjuvant chemotherapy regimen included oral UFUR/ Capecitabine (n=72, 73.4%), FL/FOLFOX/FOLFIRI (n=8, 8.2%), and CapeOX(n=18, 18.4%). All patients received surgical intervention in 12 weeks, after finishing RT.

54%(n=53) of all patients were good responders, while 46%(n=45) were poor responders. The 3-year overall OS was 87.6% for the good responders, 70.8% for the poor responders, respectively ( p = .001). The 3- year overall DFS was 86.8% for the good responders, 59.3% for the poor responders, respectively ( p = .001).

Predictors of good response on univariate LR, included volumetric modulated arc therapy (VMAT) use, RT with simultaneous integrated boost (SIB) with a CTV_H dose over 52Gy to gross tumor, higher CTV_H dose and an initial CEA concentration <5.0ng/mL. On multivariate LR, RT with SIB with a CTV_H dose over 52Gy to gross tumor ( OR 9.692; 95% CI 2.791-33.660; p = .000) and pre-treatment CEA level <5.0ng/mL ( OR 0.172; 95% CI 0.058-0.509; p = .001) remained significantly associated with good pathologic response. 

For patients with locally advanced rectal cancer, good response to neoadjuvant treatment is associated with better OS and DFS. RT with SIB in long course radiotherapy may improve the treatment response with tolerable acute toxicity.