regimen-monograph

LAPALETR

Intent

Palliative

Regimen Category

Emergent

Drugs Used

lapatinib , letrozole

A - Regimen Name

LAPALETR Regimen

Lapatinib-Letrozole

Disease Site

Breast

Intent

Palliative

Regimen Category

Emergent :

Regimens that may eventually be ‘evidenced informed’, but are still undergoing review. Regimens where one or more drugs are not approved by Health Canada for any indication will be identified under Rationale and Use.

Rationale and Uses

Post-menopausal patients with advanced hormone-receptor positive HER2 expressing breast cancer who are suitable for endocrine therapy

Supplementary Public Funding

letrozole
ODB Limited Use (letrozole - Treatment of metastatic breast cancer in hormone receptor positive postmenopausal women)

B - Drug Regimen

lapatinib

1500 mg

Daily

(Outpatient prescription in multiples of 250mg tablets)

letrozole

2.5 mg

Daily

(Outpatient prescription in multiples of 2.5mg tablets)

C - Cycle Frequency

CONTINUOUS TREATMENT

Until evidence of disease progression or unacceptable toxicity

D - Premedication and Supportive Measures

Antiemetic Regimen:

Minimal

Other Supportive Care:

Supportive care should be provided, including loperamide for diarrhea
For lapatinib-induced rash, colloidal oatmeal lotion and oral antibiotics such as minocycline 100mg PO BID have been shown to be effective. Emollients may be useful for the dry skin component of this rash.
Patients should avoid sun exposure and use sunscreens with a SPF ≥ 30

E - Dose Modifications

Doses should be modified according to the protocol by which the patient is being treated. The following recommendations are in use at some centres.

Dosage with toxicity

Suggested dose levels for lapatinib are 1500mg, 1250mg, 1000mg, 750mg and 500mg.

Toxicity	Action (lapatinib)*	Dose
Grade 2 hematologic	Hold until recovery and then restart	No change
≥ Grade 3 hematologic	Hold until recovery and then ↓ 1 dose level
≥20% decrease in LVEF from baseline or lower than institution’s lower limit of normal, or ≥ grade 3 symptoms	Discontinue and monitor patient closely; if after 2 weeks LVEF ≥ normal and patient asymptomatic may resume and ↓ 1 dose level. Monitor closely. If recurs, discontinue	_{(Continued on next page)}
Toxicity	Action*	Dose
Pneumonitis/interstitial lung disease	Hold and investigate; discontinue if ≥ Grade 3 confirmed	Not applicable
Severe changes in liver function	Discontinue	Not applicable
Grade 1-2 diarrhea	Start loperamide. If no improvement, hold until resolution. Then restart. If recurs, ↓ 1 dose level.
Grade 3 diarrhea	Hold until ≤ grade 1; treat with loperamide. When ≤ grade 1 restart with a 1 dose level ↓
Other grade 2 non-hematological	Continue, treat symptomatically. If no improvement hold until ≤ grade 1. Then restart. If recurs, ↓ 1 dose level
Other grade 3 non-hematological	Hold until ≤ grade 1 and then restart with ↓ 1 dose level
Grade 4 non-hematological	Discontinue	Not applicable

_{*Before re-treatment, major organ toxicities must recover to ≤ grade 1 within 14 days of treatment interruption; otherwise, discontinue.}

Hepatic Impairment

Hepatic impairment	Lapatinib	Letrozole
Mild	100%	100%
Moderate	Caution, consider dose ↓	100%
Severe	Extreme caution, ↓ dose and monitor closely	Monitor closely, may require dose ↓

Renal Impairment

Creatinine Clearance (mL/min)	Lapatinib	Letrozole
≥ 10	No dose adjustment appears to be required.	No change
<10	No dose adjustment appears to be required.	No data available

F - Adverse Effects

Refer to lapatinib, letrozole drug monograph(s) for additional details of adverse effects

Most Common Side Effects	Less Common Side Effects, but may be Severe or Life-Threatening
Diarrhea ↑ LFTs (may be severe) Fatigue Rash (may be severe) Nausea, vomiting Musculoskeletal pain Headache Alopecia Epistaxis Anorexia Estrogen depletion symptoms	Cardiotoxicity Arterial/venous thromboembolism Hypersensitivity Arrhythmia Pneumonitis QT prolonged Osteoporosis

G - Interactions

Refer to lapatinib, letrozole drug monograph(s) for additional details

H - Drug Administration and Special Precautions

Refer to lapatinib, letrozole drug monograph(s) for additional details

I - Recommended Clinical Monitoring

Recommended Clinical Monitoring

CBC and electrolytes; baseline and regular
Liver and kidney function tests; baseline and regular
LVEF evaluation; baseline and routine
Clinical assessment for musculoskeletal, skin, GI, GU, cardiovascular and pulmonary toxicities;
Grade toxicity using the current NCI-CTCAE (Common Terminology Criteria for Adverse Events) version

Suggested Clinical Monitoring

ECG, for patients at risk of developing QT prolongation; baseline and routine

J - Administrative Information

Outpatient prescription for home administration

K - References

Johnston S, Pippen J Jr, Pivot X, et al. Lapatinib combined with letrozole versus letrozole and placebo as first-line therapy for postmenopausal hormone receptor-positive metastatic breast cancer. J Clin Oncol 2009;27(33):5538-46.

October 2017 Formatted public funding info; new Jun 2012

M - Disclaimer

Regimen Abstracts
A Regimen Abstract is an abbreviated version of a Regimen Monograph and contains only top level information on usage, dosing, schedule, cycle length and special notes (if available). It is intended for healthcare providers and is to be used for informational purposes only. It is not intended to constitute or be a substitute for medical advice, and all uses of the Regimen Abstract are subject to clinical judgment. Such information is provided on an “as-is” basis, without any representation, warranty, or condition, whether express, or implied, statutory or otherwise, as to the information’s quality, accuracy, currency, completeness, or reliability, and Cancer Care Ontario disclaims all liability for the use of this information, and for any claims, actions, demands or suits that arise from such use.
Information in regimen abstracts is accurate to the extent of the ST-QBP regimen master listings, and has not undergone the full review process of a regimen monograph. Full regimen monographs will be published for each ST-QBP regimen as they are developed.
Regimen Monographs
Refer to the New Drug Funding Program or Ontario Public Drug Programs websites for the most up-to-date public funding information.
The information set out in the drug monographs, regimen monographs, appendices and symptom management information (for health professionals) contained in the Drug Formulary (the "Formulary") is intended for healthcare providers and is to be used for informational purposes only. The information is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects of a particular drug, nor should it be construed to indicate that use of a particular drug is safe, appropriate or effective for a given condition. The information in the Formulary is not intended to constitute or be a substitute for medical advice and should not be relied upon in any such regard. All uses of the Formulary are subject to clinical judgment and actual prescribing patterns may not follow the information provided in the Formulary.
The format and content of the drug monographs, regimen monographs, appendices and symptom management information contained in the Formulary will change as they are reviewed and revised on a periodic basis. The date of last revision will be visible on each page of the monograph and regimen. Since standards of usage are constantly evolving, it is advised that the Formulary not be used as the sole source of information. It is strongly recommended that original references or product monograph be consulted prior to using a chemotherapy regimen for the first time.
Some Formulary documents, such as the medication information sheets, regimen information sheets and symptom management information (for patients), are intended for patients. Patients should always consult with their healthcare provider if they have questions regarding any information set out in the Formulary documents.
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Last Updated: July 21, 2026

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