Gemcitabine, Docetaxel, and Capecitabine in Treating Patients With Cancer of Unknown Primary Origin

DISEASE CHARACTERISTICS:

* Histologically or cytologically confirmed malignancy for which no primary origin has been identified despite routine workup, including the following:

  * History and physical examination
  * Chemistry profile and other blood work, including tumor markers with follow up on any positive findings
  * CT scan or MRI of the chest, abdomen, and pelvis
  * Mammography (for female patients)
  * Prostate examination (for male patients)
  * Stool guaiac
* Measurable disease

  * Previously irradiated lesions are not considered measurable disease unless there is documented clear tumor progression in these lesions after completion of radiotherapy
* The following tumor types or presentations are excluded:

  * Resectable disease
  * Tumors consistent with germ cell primary, as indicated by any of the following:

    * Midline tumor
    * Elevated beta human chorionic gonadotropin
    * Elevated alpha-fetoprotein
    * i12p chromosomal alteration
  * Prostate primary with elevated prostate-specific antigen
  * Females with axillary nodes as the primary disease site
  * Tumors limited to the peritoneal cavity consistent with primary peritoneal carcinoma
  * Neuroendocrine tumors
  * Squamous cell carcinoma involving cervical or inguinal lymph nodes
* No symptomatic brain metastases

  * Prior brain metastases allowed provided patient completed definitive treatment with brain irradiation with or without resection

PATIENT CHARACTERISTICS:

Age

* 18 and over

Performance status

* ECOG 0-2

Life expectancy

* More than 3 months

Hematopoietic

* Hemoglobin ≥ 9.0 g/dL
* Granulocyte count \> 1,500/mm\^3
* Platelet count \> 100,000/mm\^3

Hepatic

* Bilirubin normal
* Meets 1 of the following criteria:

  * Alkaline phosphatase (AP) normal AND AST and ALT ≤ 5 times upper limit normal (ULN)
  * AP ≤ 2.5 times ULN AND AST and ALT ≤ 1.5 times ULN
  * AP ≤ 5 times ULN AND AST and ALT normal
* Albumin ≥ 3.0 g/dL

Renal

* Creatinine ≤ 1.5 mg/dL

Gastrointestinal

* Able to take oral medication
* Intestinal absorption intact

  * No uncontrolled diarrhea and/or daily emesis

Other

* Not pregnant or nursing
* Negative pregnancy test
* Fertile patients must use effective barrier contraception during and for 3 months after completion of study treatment
* No other malignancy within the past 5 years except curatively treated carcinoma in situ of the cervix or basal cell skin cancer
* No severe medical or psychiatric illness that would preclude study treatment
* No peripheral neuropathy \> grade 1
* No history of severe hypersensitivity reaction to docetaxel or other drugs formulated with polysorbate 80

PRIOR CONCURRENT THERAPY:

Biologic therapy

* Not specified

Chemotherapy

* No prior chemotherapy for this malignancy

Endocrine therapy

* Not specified

Radiotherapy

* See Disease Characteristics
* Recovered from prior radiotherapy
* Prior palliative radiotherapy to areas of bony metastases allowed provided there is measurable disease outside the radiotherapy port
* At least 4 weeks since prior radiotherapy
* No prior radiotherapy to ≥ 25% of the bone marrow

Surgery

* See Disease Characteristics

Other

* No concurrent antiviral therapy