Chronic Vaccination with a Therapeutic EGF-Based Cancer Vaccine: A Review of Patients Receiving Long Lasting Treatment

Therapeutic vaccines continue to be one of the most active fields in cancer research. However, despite clear evidence of antitumor effect in laboratory animals, and despite the ability of current vaccine candidates to elicit tumor specific antibodies and T-cells in humans, objective responses in the clinical trials are rare. The role of therapeutic vaccines in advanced cancer patients, if any, would be to decrease the rate of disease progression and to increase survival and quality of life. Due to the redundant regulatory loops contracting the immune response to antigens that cannot be eliminated, such a role would require chronic vaccination, which is at first sight at odds with the classic experience of vaccinology. During the last decade our team has been developing a therapeutic vaccine for advanced lung cancer, which consists of human recombinant Epidermal Growth Factor (EGF) chemically conjugated to a carrier protein from Neisseria meningitides. Several clinical trials have been carried out, showing increase in anti-EGF antibody titers, decrease in plasma EGF concentration and survival advantage in vaccinated patients. In the present paper we review data from 58 patients who were vaccinated monthly for more than one or two years. Long term vaccination was feasible and safe, and there was no evidence of cumulative toxicity. Patients kept high anti-EGF antibody titers during all the time of vaccination, without evidence of immune response exhaustion. Continued vaccination increased the probability to get a high antibody response, which has been previously shown to be, in turn, associated with a better survival. Observations done in this series of patients suggest that long term therapeutic vaccination is a feasible strategy, worth to be further explored with the aim of transforming advanced cancer into a chronic disease.