Objective This study was performed to analyze the efficacy, adverse reactions of fractional CO2 laser for atrophic acne scars, and related clinical factors. Methods: The clinical data of 121 patients with atrophic acne scars treated with ultra‐pulsed fractional CO2 laser in the Cosmetic Dermatology from August 2014 to March 2020 were retrospectively analyzed. The efficacy and adverse reactions of atrophic acne scar after fractional CO2 laser therapy were statistically analyzed. The clinical factors related to efficacy and adverse reactions after the first therapy session were analyzed by multivariate logistic regression. Results: A total of 121 patients received 206 sessions of fractional CO2 laser therapy, with an average of 1.7 sessions. Moderate to excellent improvement rate reached 50.4% after the first session. Multivariate logistic regression analysis indicated that rolling scars responded better to fractional CO2 laser treatment than icepick scars (OR = 7.3, 95% CI [1.2, 43.4], p = 0.029), and scar improvement was more significant in the high‐energy laser group than in the low‐energy laser group (OR = 10.9, 95% CI [1.1, 106.8], p = 0.041). The main adverse reactions after fractional laser surgery were pigmentation, skin sensitivity, persistent erythema, and acneiform eruption. Multivariate logistic analysis revealed that the longer the scar duration, the higher incidence of postoperative adverse reactions (OR = 1.3, 95% CI [1.1, 1.5], p = 0.008). Compared with icepick scars, rolling scars (OR = 10.4, 95% CI [2.3, 47.7], p = 0.003) and boxcar scars (OR = 12.0, 95% CI [3.3, 44.0], p < 0.001) had higher risk of developing adverse reactions. The incidence of postoperative adverse reactions was also higher in the combined mode group (DeepFX mode + ActiveFX mode) than in the single‐mode group (OR = 7.8, 95% CI [2.4, 25.5], p < 0.001). Conclusion: Fractional CO2 laser was effective in the treatment of atrophic acne scars, without serious adverse reactions. Scar type and laser energy were independent clinical factors affecting its efficacy. Scar course, scar type, and fractional laser mode were independent clinical factors affecting its adverse reactions.

Background: Merkel cell carcinoma (MCC) is a rare and aggressive neuroendocrine carcinoma of the skin, with a high recurrence rate and a high mortality rate worldwide. The purpose of this article is to construct a nomogram that incorporates significant clinical parameters and predicts the survival of individuals with MCC. Methods:The Surveillance, Epidemiology, and End Results (SEER) database was employed to retrospectively analyze all confirmed MCC cases from 2004 to 2015. The data was collected from 3,688 patients, and was randomized as the training or validation group (1:1 ratio). The independent factors which predicted the cancer-specific survival (CSS) and overall survival (OS) for MCC cases were searched for nomogram construction respectively. Independent parameters that affected CSS were determined using the Fine and Gray competing risk regression model. In addition, the time-dependent receiver operating characteristic (ROC) curve was constructed. Then, the area under the curve (AUC) values, calibration curve, and the concordance index (C-index) were used to determine the nomogram performance. At last, decision curve analysis (DCA) was conducted to determine the net clinical benefit. Results:The multivariate analysis results revealed that sex, age, race, marriage, American Joint Committee on Cancer (AJCC) stage, chemotherapy and radiotherapy were independent OS prognostic factors.Furthermore, competing risk analysis showed age, sex, AJCC stage, chemotherapy were the independent CSS prognostic factors. For validation, the C-index value of OS nomogram was 0.703 (95% CI: 0.686-0.721), while C-index value of CSS nomogram was 0.737 (95% CI: 0.710-0.764). Both C-index and AUC suggested that nomograms had superior performance to that of the AJCC stage system. In addition, according to the calibration curve, both nomograms were capable of accurate prediction of MCC prognosis. The DCA showed that the net benefits of the nomograms were superior among various threshold probabilities than these of AJCC stage system. Conclusions:The present work established and verified the novel nomograms to predict the OS and CSS of MCC patients. If further confirmed in future studies, it may become another helpful tool for risk stratification and management of MCC patients.