Logistic regression and survival analysis of 450 impotent patients treatedwith injection therapy: Long-term dropout parameters

Purpose: We report the dropout rate associated with intracavernosal self-in jection for erectile dysfunction at long-term followup, and determine param eters related to dropout. Materials and Methods: Of 2,252 impotent patients evaluated during 9 years 450 (20%) enrolled in our self-injection program. Papaverine and phentolami ne were given in 53% (initial treatment), prostaglandin E1 in 21%, and papa verine, phentolamine and prostaglandin E1 (triple mixture) in 26% of cases. Average injection volume for the 3 injection types was 0.52 cc. Data were retrospectively reviewed for patient dropout versus nondropout, specificall y for type of drug, volume injected, changing treatment (from 1 drug and/or dosage to another), patient age, marital status, ethnic group, impotence d uration and diabetes. Results: Patient age ranged from 23 to 79 years (mean age 55). Of the patie nts treated at least 4 months 155 (35%) dropped out of the study. Mean trea tment duration was 3.5 years. Logistic regression suggested that type of dr ug, changing treatment during the course of therapy and dosage (volume inje cted) were the only significant (p <0.05) parameters influencing dropout. P apaverine and phentolamine were twice as likely to lead to dropout as tripl e mixture or prostaglandin E1, and injection greater than 0.5 cc was more t han twice as likely to lead to dropout. Demographic, ethnic, age and etiolo gical factors had no significant effect on the overall dropout rate. Conclusions: The effectiveness of injection therapy was an underlying facto r determining the long-term dropout rate for patients with erectile dysfunc tion. Other parameters or combinations of parameters that may influence pat ient dropout remain to be explored.