In this prospective cohort study of primary NMSCs treated with ED&C, excision, or Mohs surgery and followed up for a median of 6.6 years, the overall tumor recurrence rate was 3.5%. Rates of recurrence after ED&C, excision, and Mohs surgery were 1.6%, 4.2%, and 3.5%, respectively.
These results fill a gap in current knowledge about treatment of NMSC. Previous data on NMSC recurrence after treatment are inadequate for several reasons. First, tumor recurrence is typically a long-term outcome, requiring collection of data for at least 5 years after treatment.10
Many previous studies (over 25% of studies in a systematic review of treatments for BCC11
) have reported follow-up data for less than 5 years. Second, in the United States, data on cutaneous BCCs and SCCs are not collected in standard population-based tumor registries, and collection of follow-up data requires direct review of medical records rather than tabulations from electronic databases. Third, NMSC is typically treated in the outpatient setting, so review of ambulatory care records, which can be difficult to access, is essential. Finally, automated data sets are usually inadequate for determination of recurrence of a given tumor because only brief and inadequate information is typically available about tumor location and recurrence status. Thus, precise determination of recurrence requires explicit a priori definitions of outcome and thorough medical record review by clinically trained staff who have access not only to dermatopathology records but also clinicians’ progress notes for at least 5 years after treatment. These requirements undoubtedly contribute to the widely acknowledged inadequacy of data about outcomes of NMSC treatment.1
The present study satisfies many of these requirements. We determined recurrence in a large consecutive cohort with long-term follow-up and for which a strict definition of recurrence was established before data collection by specialty trained clinicians. The follow-up rate was very high, in part because the ambulatory clinical records were accessible and complete.
The recurrence rate after ED&C, 1.6%, was lower than expected (a structured review reported recurrence rates after ED&C of 5.7%–18.8%11
). This difference may be related to the small number of tumors treated with ED&C (n = 127) and the fact that this treatment was typically used in lower-risk tumors.
The recurrence rate after excision, 4.2%, was similar to what was expected.11,12
The average margin size was 3.8 mm, however, and some authors have proposed that lower recurrence rates may be attainable with larger margins.13,14
The recurrence rate after Mohs surgery, 3.5%, was higher than expected. The structured review reported rates after Mohs surgery of 0.6% to 1.7%,11
and recurrence of facial BCCs after Mohs surgery in a randomized controlled trial was 2.5%.12
Our findings may not be significantly different, or they may indicate that the treatment was used in higher-risk tumors in our sample.
Tumor recurrence rates were not significantly higher in clinical subgroups with patient or tumor characteristics that are conventionally regarded as risk factors for recurrence.9
These findings may be related to an inadequate sample size to detect any differences, particularly given the low recurrence rate overall. Tumors in the H-zone of the face, however, were somewhat more likely to recur (P
= .08). Also, few patients in the sample had histories of organ transplantation or were otherwise immunocompromised, but 2 of the 7 tumors in HIV-infected patients recurred. Although the small numbers limit the conclusions we can draw from this observation, HIV infection as a risk factor for skin cancer recurrence needs further study.15,16
Some patients may have received follow-up dermatologic care outside the VA system. This possibility seems unlikely, though, since the median time between the last visit at which the patient’s skin was examined by a dermatologic clinician and his last visit to the hospital was only 6 months, indicating that most patients continued to receive follow-up dermatologic care at the VA.
This description of recurrence outcomes after treatments for NMSC must be interpreted with care. The study was conducted at a VA medical center with a limited number of providers in a single city, so the results may not be generalizable to other settings. Also, the small number of outcomes limits the precision of estimates of recurrence risk and the power of the study to detect differences in recurrence after the individual therapies. Absolute differences in recurrent rates were 2.6% (95% CI, −0.5% to 5.7%) after excision or ED&C, 1.9% (95% CI, −1.6% to 5.4%) after Mohs or ED&C, and 0.7% (95% CI, −2.8% to 4.3%) after Mohs or excision. The sample of 481 tumors undergoing Mohs or excision had 80% power to detect a difference in recurrence rates of 7%, with a 2-sided P value of .05. Comparisons in recurrence rates among the 3 groups are limited not only by this relatively low power to detect differences but also by confounding by indication because the treatment groups differed substantially in risk factors for recurrence.
The results of this study document the long-term risk of tumor recurrence in a consecutive cohort of patients with primary NMSC who were treated with the most common therapies and followed up prospectively. Overall, recurrence rates were low, particularly after ED&C.