Neoadjuvant Celecoxib and Capecitabine Combined With Pelvic Irradiation in Treating Patients With Stage II or Stage III Adenocarcinoma (Cancer) of the Rectum

DISEASE CHARACTERISTICS:

* Histologically confirmed rectal adenocarcinoma

  * Clinical stage T3, N0, M0 OR any T, N1-3, M0 disease
* Treatment with neoadjuvant chemotherapy and pelvic radiotherapy is indicated

  * All disease must be encompassable within standard pelvic radiotherapy fields
* Distal border of the tumor must be at or below\* the peritoneal reflection, defined as within 12 cm of the anal verge by endoscopy NOTE: \*If a portion of the tumor is below the peritoneal reflection at the time of surgery, patients are eligible regardless of the distance of the tumor determined at endoscopy
* Tumor must be determined to be clinically resectable

  * Tumor may not be clinically fixed
  * Negative margins by routine examination of an unanesthetized patient
* Transmural penetration of tumor through the muscularis propria by CT scan, endorectal ultrasound, or MRI
* No distant metastatic disease

  * No evidence of tumor outside the pelvis, including any of the following:

    * Metastatic inguinal lymphadenopathy
    * Peritoneal seeding
    * Liver metastases

PATIENT CHARACTERISTICS:

Age

* 18 and over

Performance status

* ECOG 0-1

Life expectancy

* At least 6 months

Hematopoietic

* Absolute neutrophil count ≥ 1,500/mm\^3
* Platelet count ≥ 100,000/mm\^3

Hepatic

* Bilirubin ≤ upper limit of normal (ULN)
* AST ≤ 3 times ULN
* Alkaline phosphatase ≤ 4 times ULN if AST \< ULN

Renal

* Creatinine clearance ≥ 30 mL/min
* No renal impairment

Cardiovascular

* No congestive heart failure
* No symptomatic coronary artery disease
* No uncontrolled cardiac arrhythmias
* No myocardial infarction
* No history of transient ischemic attacks or stroke
* No other clinically significant cardiac disease

Gastrointestinal

* No bleeding peptic ulcer disease within the past 12 months
* No lack of physical integrity of the upper gastrointestinal tract
* No malabsorption syndrome
* No active inflammatory bowel disease
* Must be able to swallow study drugs

Other

* No dihydropyrimidine dehydrogenase deficiency
* No history of uncontrolled seizures
* No CNS disorders
* No clinically significant psychiatric illness that would preclude study compliance or giving informed consent
* No other malignancy within the past 5 years except basal cell or squamous cell skin cancer or carcinoma in situ of the cervix
* No known sensitivity to NSAIDs, sulfonamides, or aspirin
* No other serious medical illness that would preclude study treatment
* No other conditions that would preclude study participation
* Must be able to tolerate major surgery that may include abdominal-perineal resection
* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective contraception during and for 30 days after study treatment

PRIOR CONCURRENT THERAPY:

Biologic therapy

* Not specified

Chemotherapy

* See Disease Characteristics
* No prior systemic anticancer chemotherapy

Endocrine therapy

* Not specified

Radiotherapy

* See Disease Characteristics
* No prior radiotherapy to the pelvis

Surgery

* See Disease Characteristics
* More than 3 weeks since prior major surgery and recovered

Other

* At least 7 days since prior nonsteroidal anti-inflammatory drugs (NSAIDs), including aspirin
* No other concurrent investigational drugs
* No other concurrent anticancer treatment
* No concurrent NSAIDs
* No concurrent primary prophylactic therapy for hand-foot syndrome
* No concurrent loperamide prophylaxis for diarrhea
* No concurrent sorivudine or brivudine