Prognostic value of pretreatment level of carcinoembryonic antigen on tumour downstaging and early occurring metastasis in locally advanced rectal cancer following neoadjuvant radiotherapy (30 Gy in 10 fractions)

Abstract

To evaluate the role of carcinoembryonic antigen (CEA) in predicting the response to and prognosis for locally advanced rectal cancer treated with 30Gy neoadjuvant radiotherapy (nRT) in 10 fractions (30Gy/10f). This retrospective study involved 240 patients with locally advanced rectal cancer who underwent 30Gy/10f nRT (biologically equivalent dose 36Gy) followed by total mesorectal excision between August 2003 and 2009. Serum CEA level was determined before administration of nRT. The prognostic value of serum CEA level on tumour downstaging and 3-year disease-free survival was analysed. Ninety out of 240 (37.5%) patients had elevated CEA levels before nRT. The incidence of T downstaging in patients decreased significantly as the pretreatment CEA levels became more elevated (<5ng/ml, 50.7%; 5-10ng/ml, 39.5%; >10ng/ml, 17.3%; P=0.00014). Downstaging to ypCR or ypStage I occurred in 46.7% (66/150) of patients with a CEA level of <5ng/ml and 34.2% (13/38) of patients with a CEA level of 5-10ng/ml. In contrast, just 13.5% (7/52) of those with a CEA level>10ng/ml downstaged to ypStage I and none of them achieved ypCR, with statistical difference (P=0.001). A significantly higher incidence of early metastasis (within 6 postoperative months) was observed with increasing CEA level: 2.0% (3/150), 5.4% (2/38) and 11.5% (6/52) in patients with CEA level<5ng/ml, 5-10ng/ml or >10ng/ml, respectively (P=0.018). Pretreatment CEA level cannot only predict tumour downstaging and ypTNM stage for rectal cancer following 30Gy/10f nRT, but also promisingly suggests a high incidence of early occurring distant metastasis. These findings may be used to select patients with nRT resistance and occult metastasis and make alternative treatment strategies.