Pretreatment Tumor Thickness as a Predictor of Pathologic Complete Response to Neoadjuvant Chemoradiation Therapy for Stage II/III Rectal Adenocarcinoma.
To evaluate pretreatment tumor thickness in predicting pathologic complete response (pCR) of stage II/III rectal adenocarcinoma to neoadjuvant chemoradiation (chemoradiotherapy [CRT]).



We retrospectively analyzed 185 patients who were diagnosed with stage II or III rectal adenocarcinoma from January 2011 to July 2013 and treated with neoadjuvant intensity-modulated radiation therapy (45 Gy in 1.8-Gy fractions to pelvis and 50 Gy in 2-Gy fractions to rectal tumor as an integrated boost) or 3 dimensionally conformal radiation therapy (45 Gy in 1.8-Gy fractions to pelvis followed by an additional 5.4-Gy to rectal tumor) concurrently with two 3-week cycles of chemotherapy (oxaliplatin 130 mg/m on day 1 and capecitabine 825 mg/m, twice per day from day 1 to 14, cycle 2 starts on week 4). One week after CRT, 36% patients received 1 more cycle of the above chemotherapy and 55% received 1 to 2 cycles of FOLFOX6. Tumor response was categorized as pCR and non-pCR. Tumor thickness measured on magnetic resonance imaging was collected. A multivariate logistic regression model was used to evaluate the association of potential predictors and pCR.



Thirty-eight patients (20.5%) reached pCR. Multivariate analysis found the pretreatment tumor thickness to be associated with higher probability of pCR after adjusting for radiation therapy-surgery interval time and pretreatment carcino-embryonic antigen level. The pretreatment carcino-embryonic antigen level was associated with pCR in the univariate analysis but lost the association in the multivatiate model. The pretreatment T or N stage, tumor volume, distance from tumor to anal verge, craniocaudal length of tumor, radiation therapy technique, and patient age and sex were not associated with pCR.



We concluded that pretreatment tumor thickness is an independent predictor for pCR of stage II/III rectal adenocarcinoma to the neoadjuvant CRT.
Departments of Radiation Oncology.
Benhua
B
Xu
Departments of Radiation Oncology.
Yuangui
Y
Chen
Departments of Radiation Oncology.
Yuyan
Y
Guo
Department of General Surgery, The First Hospital of Zibo, Zibo, Shandong, P.R. China.
Debao
D
Zhou
Institute of Life Sciences, Fuzhou University, Fuzhou, Fujian.
Zhicao
Z
Yue
Radiology.
Qing
Q
Duan
Pathology, The Fujian Medical University Union Hospital.
Yinghong
Y
Yang
General Surgery.
Guoxian
G
Guan
General Surgery.
Pan
P
Chi
Department of Radiation Oncology, University of Nebraska Medical Center, Omaha, NE.
Chi
C
Lin
D000230:Adenocarcinoma / Q000473:pathology* / Q000628:therapy; D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D059186:Chemoradiotherapy, Adjuvant / Q000401:mortality*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008297:Male; D008875:Middle Aged; D020360:Neoadjuvant Therapy / Q000401:mortality*; D009367:Neoplasm Staging; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012004:Rectal Neoplasms / Q000473:pathology* / Q000628:therapy; D012189:Retrospective Studies; D015996:Survival Rate