Successful treatment of 7,12-dimethylbenz(a)anthracene-induced hamster buccal pouch precancerous lesions by topical 5-aminolevulinic acid-mediated photodynamic therapy

Background: Our previous studies found that topical 5-aminolevulinic acid (ALA)-mediated photodynamic therapy (ALA-PDT) with a light dose of 100J/cm² is very effective for human oral precancerous lesions. Methods: In this study, 20 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch precancerous lesions were treated by topical ALA-PDT with a light dose of either 75J/cm² (n=10) or 100J/cm² (n=10) using a 640-nm light-emitting diode (LED) light to test which light dose could achieve a better clinical outcome. Results: The 10 precancerous lesions treated by 75-J ALA-PDT showed complete response in 8 after an average of 3.4 (range, 2-6) treatments and partial response in 2. The 10 precancerous lesions treated by 100-J ALA-PDT demonstrated complete response in 7 after an average of 4.4 (range, 3-6) treatments and partial response in 3. Fisher exact test showed no significant difference in clinical outcome between these two treatment modalities (p=1.000). One complete-response precancerous lesion in the 75-J ALA-PDT group recurred at the end of 19-week follow-up and another complete response precancerous lesion in the 100-J ALA-PDT group recurred at the end of 16-week follow-up. Both recurrence lesions were treated by the original topical ALA-PDT regimen and demonstrated complete response after 3 PDT treatments. Furthermore, the 5 partial-response precancerous lesions developed into squamous cell carcinomas after 30-week follow-up. Conclusion: Our findings indicate that both the 75-J and 100-J topical ALA-PDT treatment modalities are very effective for DMBA-induced hamster buccal pouch precancerous lesions and no significant difference in clinical outcome between these two treatment modalities.