Purpose: To identify prognostic factors predictive of outcome in patients with extracutaneous (stage IV) mycosis fungoides (MF) and to evaluate the risk of progression to extracutaneous disease by initial extent of skin involvement.
Patients and methods: One hundred twelve patients with extracutaneous disease at presentation or with progression and 434 patients with initial cutaneous-only disease were identified. Actuarial survival curves were plotted according to the Kaplan-Meier technique.
Results: The median survival of all stage IV patients was 13 months from the date of first treatment for stage IV disease. Sex, race, age, extent of skin involvement, and peripheral blood Sezary cell involvement were not significant to survival outcome. Eleven patients (10%) had a complete response to therapy resulting in a significantly improved median survival compared with patients with a partial or no response (1.70 v 0.91 years, P =.047 and 1.70 v 0.57 years, P =.011, respectively). At 20 years from diagnosis, the risk for progression to extracutaneous disease by initial extent of skin involvement was 0% for limited patch/plaque, 10% for generalized patch/plaque, 35.5% for tumorous disease, and 41% for erythrodermic involvement.
Conclusion: This was a larger scale study over a longer time period than had been completed previously on extracutaneous MF. Prognostic factors important in the cutaneous stages of disease are no longer significant once extracutaneous disease develops. Patients who had a more favorable response to therapy may have had a biologically less aggressive disease than their less fortunate counterparts. The risk of developing stage IV MF is highest in patients presenting with tumorous or erythrodermic skin disease and is lowest in patients with limited skin involvement.