How do you approach molecular testing in patients with gastro-esophageal cancers?

Her2 is certainly more of a binary situation. Tumors that are Her2 positive (defined as IHC 3+ or IHC 2+ and FISH +ve) benefit from trastuzumab + chemotherapy, while there are no data to support it for tumors that are Her2 negative (IHC 0/1 or IHC 2+ and FISH -ve).

So, Her2 positive tumors should absolutely receive trastuzumab + chemo or a Her2 directed 1st-line study.

The data for PD-L1 testing are more mixed. In the chemorefractory setting for esophagogastric CA, PD-L1 positive tumors are more...

Yes for HER2
There is only evidence to show benefit in first-line setting with the addition of trastuzumab. “Patients with HER2 3+ by IHC benefit most with trastuzumab. And some can live a very long time, like, 12 and 13 years” as per Jaffer A. Ajani, M.D at MDAH, so clearly there is a long term benefit in for HER2 testing

If HER2 negative, the standard of care is a combination of a platinum and a fluoropyrimidine for first line therapy. RR 50 % and median survival not exceeding one year

No for ...