Treatment: hormone therapy for breast cancer (tamoxifen, aromatase inhibitors)

• No routine laboratory tests: bone densitometry at the start of treatment, then at regular intervals.

Only depending on the situation

• FSHif neededUncertain menopausal status (hysterectomy, IUD, amenorrhoea after chemotherapy): aromatase inhibitors act only after the menopause, which must then be confirmed biochemically ^[2,3]; FSH in the menopausal range ^[4].
• LHif neededUncertain menopausal status (hysterectomy, IUD, amenorrhoea after chemotherapy): aromatase inhibitors act only after the menopause, which must then be confirmed biochemically ^[2,3]; FSH in the menopausal range ^[4].
• oestradiolif neededUncertain menopausal status (hysterectomy, IUD, amenorrhoea after chemotherapy): aromatase inhibitors act only after the menopause, which must then be confirmed biochemically ^[2,3]; FSH in the menopausal range ^[4].
• Serum calciumif needednon-French guidelineBefore anti-osteoporotic treatment decided on the basis of bone densitometry: see the page “Osteoporosis”. Hypocalcaemia after intravenous bisphosphonate is prevented by correcting vitamin D beforehand ^[4].
• Serum albuminif needednon-French guidelineBefore anti-osteoporotic treatment decided on the basis of bone densitometry: see the page “Osteoporosis”. Hypocalcaemia after intravenous bisphosphonate is prevented by correcting vitamin D beforehand ^[4].
• Serum creatinineif needednon-French guidelineBefore anti-osteoporotic treatment decided on the basis of bone densitometry: see the page “Osteoporosis”. Hypocalcaemia after intravenous bisphosphonate is prevented by correcting vitamin D beforehand ^[4].
• 25-hydroxyvitamin D (reimbursed in France) before starting exemestane (Aromasin)if neededThe exemestane SmPC (RCP) asks to consider routine 25-hydroxyvitamin D measurement before any aromatase inhibitor, because of the frequency of severe deficiency, and to supplement deficient women ^[5]; the French laboratory fee schedule (NABM) covers the test when an SmPC recommends it ^[6]. The letrozole and anastrozole SmPCs do not ask for it ^[2,3]: for these, see the next line (NR).
• 25-hydroxyvitamin D (before an intravenous bisphosphonate or denosumab, or rapid bone loss)if neededSufficient vitamin D before an intravenous bisphosphonate (prevention of hypocalcaemia); bone density loss ≥ 10% per year (or ≥ 4 to 5% if osteopenia at baseline): look for a secondary cause, including vitamin D deficiency ^[4]. Outside NABM indications ^[6].

• No routine laboratory tests: gynaecological examination before treatment, then at least once a year.

Beyond 2 years of treatment

• AST
• ALT
• GGT
• Alkaline phosphatase

Only depending on the situation

• Lipid profile (if known hypertriglyceridaemia)if neededKnown hypertriglyceridaemia: risk of worsening and of pancreatitis under tamoxifen, close monitoring ^[13].
• INR (if on a vitamin K antagonist)if neededVKA: more frequent INR checks when tamoxifen is introduced ^[13]. See the page “Treatment: vitamin K antagonist (VKA)”.
• Serum electrolytes (if risk of QT prolongation)if neededHeart disease or QT-prolonging drug: monitor the ECG and electrolytes ^[13].
• Serum magnesiumif neededThe French SmPC (RCP) asks for electrolyte monitoring in case of heart disease or QT-prolonging drug ^[13]; the UK monograph specifies potassium, magnesium, calcium and phosphate, before treatment and then according to clinical findings ^[14]. Potassium is included in the electrolytes of the previous line.
• Serum calciumif neededThe French SmPC (RCP) asks for electrolyte monitoring in case of heart disease or QT-prolonging drug ^[13]; the UK monograph specifies potassium, magnesium, calcium and phosphate, before treatment and then according to clinical findings ^[14]. Potassium is included in the electrolytes of the previous line.
• Serum phosphateif neededThe French SmPC (RCP) asks for electrolyte monitoring in case of heart disease or QT-prolonging drug ^[13]; the UK monograph specifies potassium, magnesium, calcium and phosphate, before treatment and then according to clinical findings ^[14]. Potassium is included in the electrolytes of the previous line.

Every 2 weeks for 2 months

• FBC with platelets
• AST
• ALT

Then every month for 2 months

• FBC with platelets
• AST
• ALT
• Bilirubin (if AST or ALT raised)if neededThe US labelling monitors bilirubin at each transaminase check ^[18]. The European SmPC (RCP) asks to stop abemaciclib if AST or ALT exceed 3 times normal with a bilirubin above 2 times normal, without cholestasis ^[19].