Pharmacokinetic Study of Capecitabine in Elderly Cancer Patient (≥ 75 Years)

Inclusion Criteria:

* Elderly patients 75 years old or more
* Life expectancy of greater then or equal to 6 months
* Histologically proven metastatic breast or colorectal cancer, requiring a chemotherapy by capecitabine according to the habitual schema
* Metastatic situation whatever treatment line
* Previous hormonotherapy for breast cancer, prior chemotherapy (without capecitabine) in adjuvant and/or metastatic indication (colorectal or breast cancer), or radiotherapy (colorectal or breast cancer) are allowed
* One or more measurable target lesion (RECIST criteria)
* ADL\>4 (geriatric scales)
* GSD\<12 (geriatric scales)
* Laboratory values :
* creatinine clearance (CrCl) \>=30 mL/min according to Cockcroft formula
* Adequate bone marrow function (neutrophils count \> 1.5 x 10\^9/L, platelets \> 100 x 10\^9/L, hemoglobin \[Hb\] \> 10g/dl)
* Adequate hepatic function: total bilirubin \< 1,5 x upper normal limit, aspartate aminotransferase (ASAT) and alanine aminotransferase (ALAT) \< 2,5x upper normal limits (in case of liver metastases \< 5 x upper normal limits)
* Alcalin phosphatases \<=2,5x ULN (\<=5 x ULN if liver metastases present).
* Subjects must be willing to be followed during the course of treatment/observation and follow-up.
* Signed written informed consent before first course of chemotheray

Exclusion Criteria:

* Age \< 75 years
* known brain metastases
* Concomitant oncologic treatment ongoing
* History of severe or unscheduled reaction to fluoropyrimidine treatment
* Prior unanticipated severe reaction to capecitabine or metabolites and to fluoropyrimidine therapy
* Patient with leucopenia
* sorivudine or chemical analogues treatment like brivudine
* Physiological, familial, sociological, or geographical conditions that do not permit compliance with the protocol.
* Concomitant severe affections wich lead life expectancy inferior to 3 monthes
* Uncontrolled or symptomatic angina, arrhythmias, or congestive heart failure, coronarian spasmes
* No possible oral administration
* known DPD deficiency
* Treatment with experimental therapy ongoing or within four weeks before inclusion.
* Other cancers within the last five years, with the exception of adequately treated cone-biopsied in situ carcinoma of the uterin cervix or basal or squamous cell carcinoma of the skin