The response of a rodent fibrosarcoma to superficial/interstitial photochemotherapy, chemotherapy or radiotherapy

Abstract

Growth and dose-response curves were established for a subcutaneously implanted isogenic fibrosarcoma in BD 9 rats after treatment with photochemotherapy (PCT), using Photofrin II or polyhaematoporphyrin with superficial or interstitial 630 nm light, cyclophosphamide or γ-irradiation. Tumour response to PCT increased with dose up to 200J · CM −2 for superficial light or 200J for interstitial light but no further response occurred after higher light doses. The maximum response after interstitial treatment was significantly greater than after superficial treatment where only a small margin of normal tissue was treated. The incidence of necrosis in the overlying skin was significantly less after interstitial than superficial light suggesting a better therapeutic ratio after interstitial than superficial PCT. Tumour response increased with the diameter of the treatment field after superficial light supporting the possibility of a tumour bed effect associated with PCT. The largest tumour that could be effectively treated with a single optical fibre was 12 mm. The dose-response curves for interstitial PCT and cyclophosphamide were similar but ionizing irradiation produced increasing tumour response throughout the range of doses used (5 to 30 Gy) and the maximum response was greater after radiotherapy than after PCT or chemotherapy suggesting that in this tumour model interstitial PCT is as effective as cyclophosphamide but less effective than radiotherapy.