Read on Twitter
Lobular disease accounts for more than 1 in 10 cases of breast cancer. It is often referred to as the sneaky subtype because it can evade detection. A lot has been learnt about the unique biology of lobular breast tumors, but they are still treated the same way as other subtypes.
Looking at public data, we noticed that prognosis was worse for lobular patients if tumors had a mutation in the "ERBB2" gene. This gene creates a protein called HER2. Tumors with excess HER2 respond well to HER2-targeting drugs. Lobular tumors are usually "HER2 negative".
However, lab researchers have shown that tumor cells with certain HER2 mutations grow rapidly and also respond well to HER2-targeting drugs. We thought this may be an opportunity to treat HER2-mutant lobular disease that would otherwise not qualify for HER2-targeted therapy.
To test this idea we compared lobular with the most common subtype: ductal. We found that HER2-mutants in lobular are 4 times more frequent & are more likely to respond to HER2-targeted drugs. If we do nothing, lobular patients with HER2-mutant tumors will have shorter survival.
The next step is to prove that tailored treatment for patients with HER2-mutant lobular tumors is a safe, effective and viable strategy. Gene sequencing every tumor to detect mutations would be costly. We propose measuring gene activity instead, which may be more cost effective.
HER2-mutants occur in 1 in 17 lobular cases, and as such represent one piece of the jigsaw. Even so, an additional 11,250 patients a year could benefit from HER2-targeted therapy. We need to prioritize and co-ordinate clinical trials that tailor treatments to lobular patients.
