Electrochemotherapy of skin tumours: comparison of two electroporation protocols

To study the effect of electric pulses duration and number in a sequence for electrochemotherapy of primary non-melanoma skin tumours.

Two electroporation sequences were applied: sequence A, consisting of 16 biphasic pulses of 25+25 mus duration, spaced at 0.6 ms, with a duration-number product of 0.8 ms; and sequence B, consisting of 8 50+50 mus biphasic pulses, spaced at 1.0 ms, with the same duration-number product of 0.8 ms. The two sequences were used for electrochemotherapy of clinical stage I (T1N0M0) basal cell and spindle-squamous cell carcinoma lesions in two groups of patients. Sequence A was applied to 59 patients (group A; subgroup A1 with 45 patients with basal cell carcinoma, and subgroup A2 with 14 patients with spindle-squamous cell carcinoma) and sequence B to 54 patients (group B; subgroup B1 with 40 patients with basal cell carcinoma, and subgroup B2 with 14 patients with spindle-squamous cell carcinoma). Intratumoral bleomycin was administered to all patients.

All group A and B patients achieved initially complete response (CR). The sustained CR rate in subgroup A1 patients was 80%, due to 9 recurrences and for subgroup A2 patients it was 71.4% because of 4 recurrences. No subgroup B1 patient developed recurrence. Three subgroup B2 patients showed disease recurrence, for a sustained CR rate of 78.6%.

The efficiency of electrochemotherapy in cutaneous non-melanoma tumours depends on the duration of electric pulses. For biphasic pulses, duration below 50 mus per phase (or 50+50 mus for the total pulse) is not recommended, in spite of a markedly reduced pain sensation. The rule about equal efficiency of larger number of shorter pulses and longer pulses of lesser number has its limits for external application, especially through the skin.