Background: It is well known that central-type early stage lung cancer < 1.0 cm in diameter shows almost 100% complete response (CR) to photodynamic therapy (PDT). However, we have encountered cases of local recurrence after CR of tumors with a surface diameter < 1.0 cm.
Patients and methods: Ninety-three patients with 114 lesions were followed up, and cases of recurrence after CR has been obtained with initial tumors that had a diameter < 1.0 cm were examined. We compared the cytologic findings of local recurrence after CR to the cytologic findings before PDT. The relationship between the cell features and the depth of bronchial tumor invasion before PDT and on recurrence was evaluated.
Results: The CR and 5-year survival rates of patients with lesions < 1.0 cm were 92.8% (77 of 83 patients) and 57.9%, respectively; meanwhile, in the group of patients with lesions ≥ 1.0 cm, CR and 5-year survival rates were 58.1% (18 of 31 patients) and 59.3%. There was a significant difference in efficacy between the two groups (p < 0.001). Recurrences after CR were recognized in 9 of 77 lesions (11.7%) < 1.0 cm. When the recurrent tumor cells showed type I-II (low-to-moderate atypia) at the same site initially treated, CR could be obtained by a second PDT. Type III cells (high-grade atypia) showed the characteristics of tumor cells from deeper layers of the bronchial wall. Local recurrence at the same site may be caused by residual tumor cells from deep layers because of inadequate laser irradiation and penetration.
Conclusions: To reduce the recurrence rate, it is essential to accurately grasp the tumor extent and the depth of the bronchogenic carcinoma before performing PDT. Analysis of cell features of recurrent lesions after CR appears to be a useful source of information as to the depth of cancer invasion in the bronchial wall.