What evaluations are necessary before starting tamoxifen (tamoxifen citrate) in a patient who recently underwent a lumpectomy, such as a computed tomography (CT) scan of the chest or a Pap (Papanicolaou) smear?

Pre-Tamoxifen Baseline Assessment After Lumpectomy

Before starting tamoxifen following lumpectomy, you should obtain a baseline gynecologic assessment—not a CT chest or routine Pap smear. 1, 2

Required Baseline Evaluations

Gynecologic Assessment (Required)

• A baseline gynecologic examination is specifically recommended by NCCN guidelines before initiating tamoxifen therapy 1
• This should be performed regardless of whether tamoxifen is being used for adjuvant therapy or risk reduction 2
• The gynecologic exam establishes a baseline to monitor for endometrial changes, as tamoxifen has estrogenic effects on the uterus and increases endometrial cancer risk 2, 3

Laboratory Testing (Required)

• Obtain baseline complete blood count (CBC) with platelet count 2
• Obtain baseline liver function tests 2
• These labs are necessary because tamoxifen can cause thrombocytopenia, leukopenia, and rarely pancytopenia or liver abnormalities 2

Pregnancy Testing (If Applicable)

• For premenopausal women with menstrual irregularity, obtain a negative β-HCG immediately prior to initiating therapy 2
• For sexually active women of childbearing potential with regular cycles, tamoxifen should be initiated during menstruation 2
• Tamoxifen is contraindicated in pregnancy (Category D) and can cause fetal harm 2

What Is NOT Routinely Required

CT Chest

• Routine CT chest is not indicated before starting tamoxifen (no guideline or FDA recommendation supports this)
• Chest imaging would only be appropriate if there were clinical concerns for metastatic disease, which is not part of standard pre-tamoxifen screening

Pap Smear

• Routine Pap smear is not specifically required before tamoxifen initiation 1
• While gynecologic examination is required, the guidelines do not mandate cervical cancer screening beyond standard age-appropriate recommendations
• Tamoxifen can cause variations in Pap smear results (karyopyknotic index changes, estrogen effects), but this does not necessitate baseline Pap testing 2

Additional Pre-Treatment Assessments

Breast Evaluation

• Breast examination and mammogram should be current 2
• These are typically already completed as part of the lumpectomy workup, but should be confirmed before starting adjuvant therapy 2

Contraindication Screening

• Screen for absolute contraindications to tamoxifen: 1, 2
  • History of deep vein thrombosis or pulmonary embolism requiring treatment
  • History of thrombotic stroke or transient ischemic attack
  • Current pregnancy or pregnancy potential without effective contraception
  • Known inherited clotting disorders
  • Current use of coumarin-type anticoagulants 2

Common Pitfalls

• Do not order routine endometrial biopsy or transvaginal ultrasound in asymptomatic patients before starting tamoxifen 3, 4—these are monitoring tools, not baseline requirements
• Do not delay tamoxifen for routine imaging studies like CT chest—there is no evidence-based indication for this
• Do not forget to counsel patients about the need for effective non-hormonal contraception 2—hormonal contraceptives may not work effectively with tamoxifen
• Remember that CYP2D6 genotype testing is NOT recommended before starting tamoxifen 1