Testing for efficacy

As described elsewhere on this website, any cancer therapy will, at best, only work for a subset of patients.

Cancer is a highly variable disease; each patient’s cancer will have a unique genetic make-up which will also continue to evolve. A therapy therefore only works if it "matches” a patient’s cancer biology in the intended manner and until resistant cells have evolved and started to grow. 

Personalised medicine
Increasingly, diagnostic tests are being used to select those patients who are most likely to respond to a potential therapy and/or deselect those who are not. This is done to maximise chances of success and to avoid unnecessary but potentially toxic treatment and its associated costs.

An important category of tests that are currently being tested to stratify patients for immunotherapy are so-called tumour mutational burden tests. These tests quantify the abundance of mutations in a patient’s tumour.

The to-be-validated assumption is that cancers with a high mutational burden are more likely to present tumour specific molecules and thus more likely to respond well to immunotherapy.

Similar considerations apply to bacterial immunotherapy. 

Circulating tumour DNA tests
A second very important development in cancer care are tests that aim to quantify the "tumour load” in a patient.

This information is critical in helping determine whether further treatment is required (this is no longer the case if a patient is considered cured), if a treatment should be continued (i.e. if tumour load continues to decline) or if new treatment options should be considered because a given therapy has been shown to have become ineffective.

In addition to new imaging techniques, the development of so-called circulating tumour DNA (ctDNA) tests has triggered considerable excitement.

Circulating tumour DNA tests are, as the name suggests, intended to detect circulating tumour DNA. This is DNA originating from dead cancer cells that has ended up in patient’s blood.  Since tumours comprise mutations and since blood also contains DNA originating from healthy cells, these tests are based on the detection of cancer-specific mutations.

Conclusions
The induction of an innate and especially adaptive immune response requires some time. It will therefore also take some time for bacterial immunotherapy to result in the desired immune response against cancer cells.

As described elsewhere bacterial immunotherapy promises to be an efficacious and safe treatment for those patients in whom it triggers and effective immune response. Tests on both a patient's tumour and circulating tumour DNA promise to enable the selection of those patients that benefit most.