Of 103 lesions, there were three non-responders (overall treatment response: 97.1%). Among responders (n= 100), eight local recurrences (8.0%) developed at mean 2.9 years (S = 2.7 years, range, 0.7–8.4 years), comprising a mean annual incidence rate of 1.29 recurrences per 100 person-years based on 621 person-years of follow-up time. The recurrence rate for primary treatment (7/69, 10.1%) was not significantly different from the rate for adjuvant treatment (1/31, 3.2%) (P=0.238). Variables significantly associated with recurrence in our series included a history of failed excision (P=0.001), <60 applications (P=0.04) and partial clinical clearance (P= 0.0003) [Table 1]. RFS between the lowest risk category and the highest risk category was significantly different (P=0.0001) with the low risk category demonstrating RFS 95%, compared to 50% in the high-risk group (Figure 1) at 16 years post-treatment.
Our study benefitted from long-term direction by the senior author (M.S.C.), with a relatively uniform treatment protocol in a large cohort with median follow-up of 5.1 years, including assessment by the same dermatologist or a designate familiar with the protocol. Limitations include a retrospective study design, including missing information such as post-treatment biopsy in 36% of cases, and limitations in published data which prevent weighting the model’s risk factors to represent their contribution to risk of recurrence. Despite the latter challenge, the stratification in our model is highly significant, with RFS in the low-risk group comparable to rates of recurrence with margin-controlled surgical techniques.8 While not a predictive model, this risk stratification may help clinicians frame the pre/post-treatment profile of their cases treated with topical imiquimod.
DISCLOSURES
The authors have no relevant conflicts.
REFERENCES
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7. Concato J, Peduzzi P, Holford TR, Feinstein AR. Importance of events per independent variable in proportional hazards analysis. I. Background, goals, and general strategy. J Clin Epidemiol. 1995;48(12):1495-1501. doi:10.1016/0895-4356(95)00510-2
8. Bosbous MW, Dzwierzynski WW, Neuburg M. Staged excision of lentigo maligna and lentigo maligna melanoma: a 10-year experience. Plast Reconstr Surg. 2009;124(6):1947-1955. doi:10.1097/PRS.0b013e3181bcf002
2. Hyde MA, Hadley ML, Tristani-Firouzi P, Goldgar D, Bowen GM. A randomized trial of the off-label use of imiquimod, 5%, cream with vs without tazarotene, 0.1%, gel for the treatment of lentigo maligna, followed by conservative staged excisions. Arch Dermatol. 2012;148(5):592-596. doi:10.1001/ archdermatol.2012.270
3. Weinstock MA, Sober AJ. The risk of progression of lentigo maligna to lentigo maligna melanoma. Br J Dermatol. 1987;116(3):303-310. doi:10.1111/j.1365-2133.1987.tb05843.x
4. Moreno A, Manrique-Silva E, Virós A, et al. Histologic Features Associated With an Invasive Component in Lentigo Maligna Lesions. JAMA Dermatol. 2019;155(7):782-788. doi:10.1001/jamadermatol.2019.0467
5. Swetter SM. Challenges of treating melanoma in situ, lentigo maligna type: is pathological clearance the gold standard? Br J Dermatol. 2017;176(5):1115- 1116. doi:10.1111/bjd.15512
6. Peduzzi P, Concato J, Feinstein AR, Holford TR. Importance of events per independent variable in proportional hazards regression analysis. II. Accuracy and precision of regression estimates. J Clin Epidemiol. 1995;48(12):1503- 1510. doi:10.1016/0895-4356(95)00048-8
7. Concato J, Peduzzi P, Holford TR, Feinstein AR. Importance of events per independent variable in proportional hazards analysis. I. Background, goals, and general strategy. J Clin Epidemiol. 1995;48(12):1495-1501. doi:10.1016/0895-4356(95)00510-2
8. Bosbous MW, Dzwierzynski WW, Neuburg M. Staged excision of lentigo maligna and lentigo maligna melanoma: a 10-year experience. Plast Reconstr Surg. 2009;124(6):1947-1955. doi:10.1097/PRS.0b013e3181bcf002
AUTHOR CORRESPONDENCE
M Shane Chapman MD MBA Michael.Shane.Chapman@Hitchcock.org
