This is a dosage escalation study to estimate the maximum tolerated dose of 9-cis-retinoic acid given in combination with tamoxifen. Groups of 3 to 6 patients receive oral 9-cis-retinoic acid daily for 4 weeks, after which daily oral tamoxifen is added to the regimen. Patients continue treatment for up to 28 weeks, with tamoxifen continued after the study if medically appropriate.

This is a Phase I study of the combination tamoxifen and 9-cis-Retinoic acid in patients with breast cancer. The primary objective of the study is; 1) to determine the maximum tolerated dose of 9-cis-Retinoic acid in combination with Tamoxifen and to determine the overall and dose limiting toxicities. Other objectives are: 2) to determine the effect of Tamoxifen on the pharmacokinetics of 9-cis-Retinoic acid; 3) to evaluate the anti-tumor activity of this combination therapy within the context of a phase I study; 4) and to determine the expression of surrogate biomarkers of breast carcinogenesis before and after treatment.

DISEASE CHARACTERISTICS:

All patients must have histologically documented diagnosis of Stage III, or IV breast carcinoma.

Patients with stage III that has completed chemotherapy: Estrogen receptor (ER) or progesterone receptor (PR) positive tumor required if premenopausal. Either ER/PR-positive or -negative tumor allowed if postmenopausal and have received prior chemotherapy.

Patients may have stage IV with ER/PR-positive or -negative tumor.

No CNS metastases, pseudotumor cereri, or seizures.

PRIOR/CONCURRENT THERAPY:

Patients who have ecovered from the toxic effects of prior therapy will be eligible.

Patients with prior tamoxifen will be allowed to participate. At least 3 weeks must have elapsed since the last dose of chemotherapy.

PATIENT CHARACTERISTICS:

Age: 18 and over.

Sex: Men and women.

Menopausal status: Any status.

Patients must have a performance status of ECOG 0-2.

Patients must have Hematopoietic criteria of:

ANC at least 1,500/mm(3).

Platelet count at least 90,000/mm(3).

Patients must have Hepatic criteria of:

In the absence of tumor involvement:

Bilirubin no greater than twice normal;

SGOT no greater than twice normal;

Alkaline phosphate no greater than twice normal;

Fasting triglycerides less than 3 times normal.

Patients must have Renal criteria of:

Serum creatinine no greater than 1.5 mg/dL OR;

Creatinine clearance at least 60 mL/min.

Other:

No allergy to study medications.

No nonmalignant systemic disease that would preclude therapy.

No second malignancy within 5 years except: Curatively treated basal cell skin carcinoma. Cervical carcinoma in situ.

Pregnant women will be excluded.

Negative pregnancy test required within 7 days prior to entry.

Adequate contraception required for 4 weeks prior to, during, and for 1 year after study.

Patients must give informed consent.

Patients who are poor medical or psychiatric risks will be eligible.