A novel nomogram based on a retrospective study of 346 patients to predict the recurrence risk of condyloma acuminatum after 5-aminolevulinic acid photodynamic therapy

Condyloma acuminatum (CA) is a sexually transmitted disease caused by human papillomavirus (HPV) often with high recurrence rate after treatment. This study aimed to construct and evaluate a nomogram model containing three clinical parameters to predict the recurrence risk of CA after 5-aminolevulinic acid photodynamic therapy (ALA-PDT). A predictive model was established based on a training cohort of 346 CA patients treated with ALA-PDT between January 2013 and July 2018. A validation cohort of 123 CA patients was recruited from August 2018 to December 2019. The least absolute shrinkage and selection operator (LASSO) regression model was used to optimize the clinical feature selection. A nomogram predicting the recurrence of CA after ALA-PDT was constructed based on the predictors identified by LASSO regression. C-index and area under the curve (AUC) values were used to evaluate the discrimination. Calibration was evaluated with a calibration curve. The net benefit was performed via decision curve analysis (DCA). In the training cohort, 55 (15.89%) patients experienced recurrences after ALA-PDT. Predictors selected by LASSO regression were concomitant human immunodeficiency virus (HIV) infection [Hazard ratio (HR) = 4.4; 95% confidence interval (CI), 2.5-7.9; p < 0.001], skin and mucosa as affected area (HR = 1.7; 95% CI, 0.9-3.1; p = 0.109), and more than one time of CO2 laser therapy (HR = 6.3; 95% CI, 2.8-13.9; p < 0.001). The nomogram showed a good performance in predicting recurrence as the C-indexes were 0.843 (95% CI, 0.799-0.887) in the training cohort, and 0.831 (95% CI, 0.727-0.934) in the validation cohort. The AUCs of the nomogram were 0.85 in training and 0.8 in validation. DCA confirmed the nomogram was clinically useful when the intervention was determined at the non-adherence possibility threshold of 5%. This nomogram can provide individualized prediction for the recurrence risk of CA in patients treated by ALA-PDT.