Possible enhancement of vincristine neuropathy by VP-16.

Eleven consecutive patients with small cell carcinoma of the lung treated intensively with a combination chemotherapy regimen cyclophosphamide, Adriamycin, VP-16, and vincristine experienced peripheral neuropathy. Four of the 11 patients had severe (Grade III) neuropathy, leaving them virtually bedridden; the remaining seven patients had mild to moderate neuropathy. Only 8 of the 14 patients treated less intensively with vincristine and VP-16 had Grade I and II neuropathy. Predisposing factors for severe neuropathy included advanced age and preexisting peripheral neuropathy. All patients' performance status declined and all lost much weight before developing neuropathy. From accumulated treatment experience of small cell carcinoma with vincristine alone or with vincristine, Adriamycin, cyclophosphamide combinations, the authors feel that the severe neuropathy observed was due to an interaction of vincristine and VP-16. This conclusion is supported by electron microscopic observation of electronopaque granular degeneration of the myelin lamellae of affected nerve fibers.