Treating micrometastases, that are more vulnerable than original tumors, with immunotherapy before surgery could prevent even genetically more homogeneous tumors from killing the host.

Before only genetically highly heterogeneous cancers with many mutations induced by, for example, sun exposure (melanoma) or DNA mismatch repair dysfunction were sensitive to the immunotherapy. 

"High-relapse cells-rich micrometastases were infiltrated with immune T cells, yet became progressively immune-excluded during outgrowth. Treatment with neoadjuvant immunotherapy (before  surgery) eliminated residual metastatic cells and prevented from relapsing after surgery." [1]

1. Metastatic recurrence in colorectal cancer arises from residual EMP1+ cells. Adrià Cañellas-Socias … & Eduard Batlle. , Nature, 9 November 2022.