Dear
sisterofher2+, I am not sure if you understand how cancer metastasises? HER2+ breast cancer is highly prone to metastasizing, so is a bit like melanoma skin cancer in this way, where some other breast cancers are much less prone to metastasizing like common squamous cell carcinoma. When a cancer that is highly prone to metastasizing changes from an "in situ" cancer to an invasive cancer, it starts to slough off cancer "seeds" known variously as metastatic cancer cells, cancer stem cells, stem-cell-like cancer cells. They can transform back and forth from very primative menenchymal cell form to a very typical epithelial cell form.Some of these cells stay in the tumor They are then capable of changing the gene-line of the tumor cells to ones that use different pathways enabling them to get around pathways initially blocked by drugs or radiation. This makes the next generation of tumor cells resistant to that specific drug or treatment. Some of these cancer seeds float off in lymph fluid or blood, and are not always able to be targetted by any treatments because they don't divide much at that stage. They hunt out suitable spots in mostly in brain, liver, lungs and bones, and grow into metastatic breast cancers. Luckily the new drugs for HER2+ cancers including herceptin, perjeta and others are good at seeking out these baby metastatic cancers where cells are dividing quickly, and killing them off. Each of the new ones targets diff pathways which gets around the resistance problem.
This metastasing process is the biggest risk that confronts all of us with HER2+ breast cancer, whether or not we already have metastatic cancer. This is what will kill us if we are to die of this cancer. HER2+cancer used to kill over 50% of those who got it, even when caught very early, whatever the patient did in terms of good personal health care, diet, exercise, apricot kernels etc. Now with the new drugs, that drops to between 2% and 20% depending on diagnosis. For those who are ER+ Tamoxifen and Aromase Inhibiters and the new hormone treatments that cut the estrogen in the body down to a minimum, modifying the hormonal environment means the cancer seeds are much more likely to fall on infertile ground where they cannot grow. The 5yrs/10yrs issue I understand is about how long changing this hormone environ continues to produce a big drop in new metastases. I had a friend who got a dozen golfball sized metastatic tumors in liver and lungs within months of stopping tamoxifen after 6yrs on it. Luckily with intensive weekly chemo and herceptin and hormone treatment for a year, they have gone again. But it demonstrated quite clearly for her what a difference that hormone treatment was making. Everyone is different and the diff it makes depends on how strongly ER+ one is.
So even if some of these alternative treatments can help prevent primary cancers, unless they can provide powerful protection against metastatic cancer stemcells, they are not going to be nearly as much help to your sister as the Herceptin-family of drugs, the chemo most effective in combination with those, and the estrogen-reducing drugs.
Your sister may well, like me, be currently mostly concerned with the inner battle to put aside fear when standing in the shadow of death which is what it means to have this sort of cancer. For me, I have my treatment plan, I have good medical team, I really don't want others revamping this for me, because I have other places I want to be putting my energy. I strongly suggest you ask her to tell you frankly and honestly how you can be the best sister to her at this really tough time for her. It is really important to be sure you are helping her not hindering, and that you keep checking with her that you are not getting it wrong. This time could bring you and your sister close, or it could divide you in a very sad way if you get it wrong.