Can Radiotherapy Produce a Cancer Vaccine Effect?

According to a study presented at the 2017 San Antonio Breast Cancer Symposium, radiotherapy irradiation of the tumor area causes tumor DNA fragments to accumulate inside cancer cells, producing a kind of cancer vaccine effect.

What Is a Cancer Vaccine, and How Does It Work?

There are 2 types of cancer vaccines: preventive and therapeutic.

Preventive cancer vaccineshave been used successfully for decades and provide highly effective protection against the microbes for which they were developed. For example, the HBV vaccine developed against hepatitis-B virus provides protection against liver cancer, while the vaccine against human papillomavirus , the HPV vaccine, provides highly effective protection against cervical cancer.

Therapeutic cancer vaccines with effective forms are newer in cancer medicine, and so far only 2 cancer vaccines have been approved for cancer treatment: for prostate cancer treatment, sipuleucel-T (Provenge) and for the treatment of the skin cancer malignant melanoma, talimogene laherparepvec (Lmlygic). These vaccines do not promise a complete cure for the cancer types for which they are approved. In this respect, therapeutic cancer vaccines can be said to be less effective than preventive vaccines, because preventing cancer before it develops is easier than treating it afterward! In addition, the still-popular Cuban cancer vaccines have not yet received approval for use in any cancer type because they have not demonstrated meaningful effectiveness.

• The reality of cancer in Cuba according to Cuba’s own official data

Therapeutic cancer vaccines aim to enable the immune system to recognize the tumor and activate the immune system against it. Cancer develops in our bodies not so much because the immune system weakens, but because tumors develop mechanisms to hide from the immune system as they grow. Cancer, immunotherapies when made recognizable to the immune system through interventions such as these, is easier to treat. Cancer vaccines are only one type of immunotherapy (see the graph below).

How Does Radiotherapy Work Like a Cancer Vaccine?

While radiotherapy triggers cancer cell death, cancer-cell DNA fragments and other cellular components can attract or activate T cells, which are immune system cells, in the tumor environment. Normally, in the tumor microenvironment our immune system cells are dormant or coexist in harmony with the tumor. Under the effect of radiotherapy, they may begin working in our body’s favor again.

Findings from cell cultures, mouse models and early clinical studies in human patients showed that:

• In cancer cells exposed to increasing radiation doses, double-stranded fragments of tumor DNA accumulated in the cytoplasm,
• Damaged DNA fragments activated the exonuclease 1 (Trex 1) enzyme, a member of the DNA repair system,
• This triggered the immune system through interferon beta (INFb).

In this way, radiotherapy acts like an in situ cancer vaccine , and this is also called “abscopal immunogenicity.”

Based on these findings, the research team initiated a clinical study in stage 4 non-small cell lung cancer, combining the new-generation immunotherapy medicine ipilimumab (Yervoy) with radiotherapy.

Additional research is being conducted to determine the cancer types and treatment sequences in which this approach will be most effective.