PROGNOSTIC TREES TO AID PROGNOSIS IN PATIENTS WITH CUTANEOUS MALIGNANT-MELANOMA

Objectives-To design user friendly guides to prognosis for patients wh o have had invasive primary cutaneous malignant melanomas surgically e xcised. Design--Adaptation of the classification tree method was used to derive prognostic trees for four different subgroups of malignant m elanoma patients in whom known and possible prognostic variables inter acted in different ways. Setting-Scotland. Subjects-Statistical modell ing for prognostic trees was based on 1978 patients whose primary mali gnant melanoma was first diagnosed in 1979-86 for whom five year follo w up and all relevant clinical pathological data were available, The r esultant model was validated with 300 patients first diagnosed in 1987 for whom the same information was available. Main outcome measures--A ctual and predicted rate of survival after diagnosis of primary cutane ous malignant melanoma. Results--The four subgroups of patients were m en and women with ulcerated and non-ulcerated cutaneous primary melano mas. Validation of the model showed excellent agreement between actual status of patients in the relevant subgroups and their status as pred icted by the model. Conclusions--The prognostic trees are simple to us e and give more accurate prognosis for individual patients than is cur rently available from tumour thickness alone.