RATIONALE: Drugs used in chemotherapy, such as gemcitabine, work in different ways to stop the growth of tumor cells, either by killing the cells or by stopping them from dividing.

PURPOSE: This phase II trial is studying how well gemcitabine works in treating patients with metastatic cancer of unknown primary.

OBJECTIVES:

• Evaluate the efficacy of gemcitabine hydrochloride in patients with metastatic cancer of unknown primary (CUP), in terms of improved quality of life (QOL) (as measured by the FACT Physical Well Being subscale [FACT-G]) and reduction of symptom distress (as measured by the Memorial Symptom Assessment Scale Short Form Global Distress Index [MSAS-SF]).
• Define clinical benefit response using a QOL instrument in patients with CUP receiving gemcitabine hydrochloride.
• Correlate objective and/or evaluable tumor response with symptom and QOL response in these patients.
• Explore the association between symptom response, QOL response, and clinical benefit response in these patients.
• Evaluate changes in QOL in patients who have no symptom or objective response after treatment with gemcitabine hydrochloride.
• Correlate EuroQOL ratings with those using symptom instruments (MSAS-SF) and quality of life instruments (FACT-G).
• Evaluate changes in perceived QOL, as measured by the EuroQOL instrument, and how these changes relate to symptom response and QOL response.
• Evaluate the patient's assessment of treatment burden, as measured by a single question, and how this compares to symptom response and QOL response.

OUTLINE: This is an open-label, multicenter study.

Patients receive gemcitabine hydrochloride IV over 30 minutes on days 1, 8, 15, 22, 29, 36, and 43, followed by 1 week of rest (course 1). For all subsequent courses, patients receive gemcitabine hydrochloride IV over 30 minutes on days 1, 8, and 15. Treatment repeats every 4 weeks for up to 6 courses in the absence of disease progression or unacceptable toxicity.

Quality of life (QOL) and symptom response are assessed at baseline and at weeks 8, 16, and 32 (end of treatment). Questionnaires include the Memorial Symptom Assessment Scale-Short Form, Functional Assessment of Cancer Therapy-General, Pain Visual Analog Scale, and EuroQOL. Patients' perception of symptom response and perception of treatment burden are also assessed.

After completion of study treatment, patients are followed periodically for up to 3 years.

PROJECTED ACCRUAL: A total of 52 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

• Histologically confirmed poorly differentiated carcinoma or adenocarcinoma of unknown primary

  • Diagnosis based on biopsy and conventional imaging, including CT scans of the chest, abdomen, and pelvis with or without positron emission tomography (PET) scans or other specialized tests, performed within the past 4 weeks

• Must not have any of the following clinical features:

  • Squamous cell carcinoma in the lymph nodes of the neck or inguinal nodes only
  • Women with axillary lymph node metastases only
  • Women with peritoneal carcinomatosis only
  • Well-differentiated neuroendocrine tumors
  • Poorly differentiated tumors with midline tumor or elevated human chorionic gonadotropin (HCG)/alpha-fetoprotein (AFP)
  • Men with adenocarcinoma and elevated prostate-specific antigen (PSA)

• Measurable disease

• No symptom emergency at the time of study entry including, but not limited to, the following:

  • Back pain with epidural cord compression
  • Large effusions causing distress
  • Hypercalcemia
  • Bowel obstruction
  • Very painful (worst pain 10/10) solitary bone metastases with impending fracture

PATIENT CHARACTERISTICS:

• Modified "Physical Well-Being" subscale of the FACT-G score ≥ 6 within the past week
• Pain-intensity score ≥ 20 mm on the Memorial Pain Assessment Card OR receiving analgesics of ≥ 10 mg per day of oral morphine equivalent within the past week
• ECOG performance status 1-2
• WBC ≥ 3,000/mm³
• Platelet count ≥ 100,000/mm³
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception
• Able to read, understand, and complete the quality of life and symptom questionnaires, and perception of change
• Able to complete the analgesic diary on a daily basis

PRIOR CONCURRENT THERAPY:

• No prior chemotherapy or radiation therapy