PDE5 inhibitors (Viagra etc) and herceptin

Pops1

Hi there. I have a bit of a strange request on behalf of my 32yo daughter with HER2+ metastatic breast cancer. I recently came across this article titled "Phosphodiesterase Type 5 Inhibitors Increase Herceptin Transport and Treatment Efficacy in Mouse Metastatic Brain Tumor Models" about work that has been done on improving the uptake of Herceptin into the brain to treat brain metastases by taking PDE5 inhibitors (Viagra type of drugs for treating ED). The research was looking positive but was not taken further due to lack of funds.

We fully understand that this approach may not be successful as it has only been trialled on rats and mice and not in humans but we feel that nothing ventured nothing gained and as we are running out of other options we have nothing to lose. Her oncologist is not keen for her to try this as she says that the side effects of mixing these two drugs is unknown.

I know that MBC is fairly rare and that HER2+ is even rarer but I wondered if there was anyone on the forum that had been prescribed both Herceptin and a PDE5 inhibitor and if so what if any side effects were?