PHOTODYNAMIC THERAPY OF SQUAMOUS-CELL CARCINOMA - AN EVALUATION OF A NEW PHOTOSENSITIZING AGENT, BENZOPORPHYRIN DERIVATIVE AND NEW PHOTOIMMUNOCONJUGATE
Aw. Hemming et al., PHOTODYNAMIC THERAPY OF SQUAMOUS-CELL CARCINOMA - AN EVALUATION OF A NEW PHOTOSENSITIZING AGENT, BENZOPORPHYRIN DERIVATIVE AND NEW PHOTOIMMUNOCONJUGATE, Surgical oncology, 2(3), 1993, pp. 187-196
Photodynamic therapy for cancer depends on the relatively selective di
stribution of photosensitizing agents to malignant as compared with no
rmal tissues, rendering the malignant cells more susceptible to light-
mediated damage. Photodynamic therapy has been used with only moderate
success to date. The purpose of this study was to compare a new photo
sensitizing agent, benzoporphyrin derivative (BPD), to the standard ag
ent presently in use, photofrin II, in a hamster cheek pouch model of
squamous cell carcinoma. As well we have investigated the potential of
using a tumour-specific monoclonal antibody-BPD conjugate to improve
the tumour localizing properties of BPD. Treatment consisted of photod
ynamic therapy with either photofrin II, BPD, or a tumour-specific ant
i-epidermal growth factor receptor-BPD conjugate. Control groups of li
ght alone, anti-EGFr, tumour non-specific MoAb, and tumour non-specifi
c MoAb-BPD conjugate were included with the contralateral cheek pouch
of each animal acting as a dark control. An assessment of differential
delivery of BPD to tumour and to normal mucosa was undertaken using a
spectrophotometric assay. Parametric statistical analysis included St
udent's t-tests and linear regression while non-parametric analysis wa
s undertaken using Fisher's exact test. Animals receiving BPD alone de
monstrated tumour-to-tissue levels of approximately 2:1 while animals
receiving the tumour-specific anti-EGFr-BPD conjugate had significantl
y better tumour:tissue ratios of 26:1 (P < 0.005). Animals treated wit
h photofrin II had a 1 month cancer-free survival of 27% while animals
treated with BPD had an improved survival of 67% (P=0.03) The group t
reated with the tumour-specific anti-EGFr-BPD conjugate at a twentieth
the total dose of BPD had an 80% 1 month cancer-free survival which w
as not statistically different from the group treated with BPD alone.
Benzoporphyrin appears to be a more effective photosensitizing agent t
han Photofrin II and its tumour selectivity can be improved using a tu
mour specific monoclonal antibody conjugate.