The Relation Between Serum CEA Response and the CTscan Finding After Neoadjuvant Therapy in Rectal Cancer Patients

ABSTRACT

Serum Carcinoembryonic Antigen (CEA) levels are the most widely used tumor marker for colorectal cancer. Elevated serum CEA has been reported to be associated with an increased risk of relapse and poor patient outcome. Whether this marker would be altered with preoperative adjuvant treatment of rectal cancer prior to resection and can this alteration reflect any changes in the tumor have not been yet investigated. If so, this might guide us to predict curative from palliative resection and to correlate between the marker level and future tumor response to the adjuvant therapy. Aim: This review was undertaken to assess the effect of preoperative neoadjuvant therapy on serum CEA level and the relationship between these effect on CEA and changes of the tumor in CT scan in advanced rectal cancer patient before definitive surgery.

Methods: Between January 2002 and October 2007, a retrospective review using the colorectal database for all rectal cancer patients treated in King Faisal Specialist Hospital and Research Center was performed. All patients received preoperative long course radiotherapy alone, or combined with 5- fluorouracil. Serum CEA and CT scan was done for the patients before starting the neoadjuvant therapy, and repeated again prior to surgery. Surgical resection was planned 6 – 8 weeks following the completion of treatment. We determined the criteria of the tumor response in the CT scan findings and compared the results with the CEA level after the neoadjuvant therapy.

Results: Out-off the 77 patients, 38 received radiotherapy alone, while 39 patients received chemoradiotherapy, CT scan was done for all patients in both groups (pre and post neoajuvent therapy).

Patients divided into 2 groups based on the CT scan findings to: CT responder and CT non-responder patients. In the radiation only group, 21 (55 %) patients had raised CEA levels before the treatment, 18 (86%) of them showed a decrease in CEA with CT response, while 3(14%) patients’ demonstrated further increase and CT non-response. 17(45%) patients with normal CEA. 15 (89%) of them showed normal CEA post treatment 12 (80%) of them showed CT response and 3 of them shows CT non-response. 2/17 (11%) patients showed further increase in CEA level and CT non-response as well.

In the chemoradiotherapy group, 17 (43%) patients had high CEA level before the treatment. 16 (95%) of them showed a decrease in CEA and CT response while 1(5%) patient showed increase in CEA level and CT non-response post treatment. 22/39(57%) showed normal CEA where all of them remained in normal level post treatment and only 1 patient (5%) showed CT non-response.

All patients with CEA and CT scan response are operable patients and we can consider them for curative resection, while all patients with CEA and CT scan non response are non operable or can get a palliative treatment due to ( metastasis or carcinomatosis).

4 patients of normal CEA post treatment CT scan shows ( increase in thickening and single new lesion in the liver with suspicious of metastasis ) but still operable patients with intension to cure. Conclusions: There is an obvious relation between serum CEA level and CT scan findings during neoadjuvant therapy. CEA level post neoadjuvent therapy can differentiate between operable and non operable patients. CT scan can be used for patients with increase CEA level as further investigation before surgery and can be eliminated for those with CEA normal or dropped level.

Further studies are needed to correlate this finding with post operative histopathological finding and patient outcome