The role of cancer vaccines following autologous stem cell rescue in breast and ovarian cancer patients: experience with the STn-KLH vaccine (Theratope).

The success of high-dose chemotherapy followed by autologous stem-cell rescue as treatment for breast and ovarian cancer is limited by a high incidence of relapse. After autologous transplantation, patients are likely to have a low tumor burden and thus would be more likely to respond immunologically to a cancer vaccine. Sialyl-Tn (STn) is a carbohydrate associated with the MUC1 mucin on breast and ovarian cancer and is an ideal candidate for vaccine immunotherapy. Sialyl-Tn-keyhole limpet hemocyanin (STn-KLH) vaccine (Theratope) incorporates a synthetic STn antigen that mimics the unique tumor-associated STn carbohydrate and is designed to stimulate tumor antigen-specific immune responses in patients with mucin-expressing tumors. Between 1995 and 2000, 70 patients (16 with stage II/III breast cancer, 17 with stage III/IV ovarian cancer, and 37 with stage IV breast cancer) were treated with 2 different formulations of STn-KLH. Toxicity, outcome, and immune response data are reported. STn-KLH was well-tolerated with minimal toxicity. The most common side effects were indurations and erythema at the sites of injections. Humoral and cellular responses were elicited in the majority of patients. Overall, these data indicate that post-autologous transplant patients are able to mount an effective immune response to vaccine immunotherapy with minimal side effects, and that vaccine immunotherapy may be a useful addition to high-dose chemotherapy regimens.