24P - Outcomes of patients with HER2 positive metastatic breast cancer treated with low dose or metronomic lapatinib

Background

Lapatinib at an approved dose of 1250 to 1500 mg/day in Her2 positive metastatic breast cancer contributes to a high pill burden and financial toxicity. Hence the concept of “value meal” has been suggested, i.e. increasing the bioavailability by giving lower doses of lapatinib with meal, as suggested by phase I studies.

Methods

In our institution, for patients with Her2 positive metastatic breast cancer who cannot afford the approved dose of lapatinib or other Her2 agents, low dose or metronomic lapatinib, 500mg daily with meal, is offered. We conducted a retrospective review of the safety and efficacy of this regimen, including data from January 1, 2014 to December 31, 2020.

Results

A total of 47 females were enrolled. The majority had de novo metastatic disease (n=27,57.4%) and multiple visceral metastases (n=23,48.9%). The median number of lines of treatment before lapatinib was one. Lapatinib was given in combination, but 4 patients received it as a single agent. The disease control rate with lapatinib was 61.7%, out of whom 4.3% (n=2) experienced complete remission. The median progression free survival was 7 months (95% CI: 5.6 - 8.4 months), with a median overall survival of 12.5 months (95% CI: 9.7 - 15.3 months). The median duration of response was 4.5 months, ranging from 1.3 months to 45.8 months. The low-dose lapatinib was well-tolerated. Only eleven patients (23.4%) experienced some toxicity, with grade 3 in only one (2.1%) and no grade 4 toxicities. The most common toxicities were skin rashes and hand-foot syndrome. Dose interruptions were necessary in 3 (6.4%) patients, while drug was discontinued in one (2.1%).

Conclusions

The disease control rate and the progression free survival with low dose lapatinib is equivalent to the standard dose in published literature. The overall survival is short here as many did not receive any further anti-Her2 agents in view of financial toxicity. As a well tolerated regimen with less financial burden, this is an approach that needs further validation in larger randomised controlled trials.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Malabar Cancer Centre.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.