The six-day subrenal capsule assay (SRCA) for testing the response of human tumours to anticancer agents. Validity and usefulness in cancer research and treatment.

To assess the value of the 6-day subrenal capsule assay (SRCA), the growth of human tumours under the kidney capsule of immunocompetent mice as well as the response of the grafts to chemotherapy were studied and compared with the results obtained when the same tumours were grown subcutaneously (SC) in athymic, nude mice. Human tumours serially transplanted in athymic mice were used as test material. The subrenal grafts increased rapidly in size and showed individual, characteristic and reproducible growth rates and they retained the morphological and functional characteristics of the parent tumours, including their malignant character. The infiltration of the grafts by host cells, demonstrable already after day 4, contributed some 15-35% of the total graft volume on day 6 but did not seriously interfere with the growth measurements and the assay. When the chemosensitivity of different tumours was tested both in the 6-day SRCA and in the subcutaneous nude mouse model, the same ranking of drugs was obtained with the two procedures. The results show that the 6-day SRCA on tumour xenografts permits reliable and meaningful measurements of the response of human tumours to drugs. The data indicate that the assay deserves a wider use in cancer chemotherapy and research.