Ann: Imugene HER-Vaxx and CHECKVacc to be Featured at ESMO, page-123

I would suggest that the biopsy information is efficacy related.
As in,
"We injected this, the cancer died, we think it was because of our virus, there appears to be a correlation. So we took some samples of the necrotic tissue and had it analysed.
Turns out there's a whole bunch of virus in the dead cells and they exploded from the inside, we can safely suggest the virus replicated and causes widespread lysis of the cancer cells."
Or something to that effect. I have no idea what they look for with the biopsy other than if the cells are dead and in the past, they would analyse boundaries of the cancer and healthy cells etc etc.
It would have been a good question to ask Prof Fong (what do they look for in the biopsies).

So by presenting the biopsy data, they can say that they found the treatment to be safe, and they can infer the cancer was killed by the virus. Effectively showing causation, not just a correlation.
My speculation, nothing more.