Several groups have recently reported their experiences monitoring patients at risk for melanoma with either serial DELM photography10, 11, 20
or TB photography.5, 12, 17, 21
Compared to prior studies using TB photography reported in the literature,3, 5, 12, 17, 21-25
our study presented here describes the largest number of patients and melanomas detected (to our knowledge). More importantly, we have been able to evaluate this approach in the context of our prior experience with serial DELM photography14
involving the same physicians seeing a similar patient population. Five years ago, we began using TB photography to address critical limitations we found in our preceding experience with serial DELM photography14
– namely melanomas presenting as new lesions or arising in benign-appearing nevi that had not been previously photographed.
The validity of comparing the results here with those from our previous photographic study14
is justified by a similar composition of melanoma risk factors in the patients from each cohort. In fact, over 60% of the patients in the prior study were part of the second cohort described here. Moreover, we found comparable rates of melanoma incidence in the two groups (0.026 vs. 0.020 per patient, p=.81) monitored by TB compared to serial DELM photography, consistent with the two populations representing individuals with similar melanoma risk. We monitored a greater number of patients with TB photography (467 vs. 297), but the range (2-54 vs. 3-52 months) and median (24 vs. 22 months) for the monitoring periods were comparable (). For both cohorts, far fewer lesions were biopsied compared to what one might expect from the common practice of many dermatologists to remove one or two atypical nevi at each visit.4
One study of melanoma patients (approximately one third with numerous nevi) in which photography was not used, reported an average of 17 nevi (from those with numerous nevi) and three nevi (from entire cohort) removed per patient over a four-year period.26
By contrast, we achieved extremely low biopsy rates on follow-up visits with both approaches (0.59 biopsies per patient with TB photography vs. 1.1 per patient with DELM photography,14
p<.001, ). The significantly higher biopsy rate with DELM photography may be a consequence of the greater sensitivity for detecting morphologic changes in nevi due to higher resolution of these photographs, and the fact that we were more likely to biopsy lesions exhibiting photographic change. In the previous study,14
however, we had only one case where a changing nevus proved to be a melanoma. Thus serial DELM photography appears more likely to identify morphologic changes that are histologically (or clinically) insignificant.
We found a higher rate of melanoma detection in patients monitored by TB photography (5.5% vs. 2.2%, ). Our previous finding that lesions exhibiting subtle dermatoscopic changes rarely proved to be melanoma14
may account for the lower detection rate with DELM monitoring. On the other hand, the higher detection rate we found with TB photography suggests that this method may be more specific for melanoma detection. Although the invasive lesions detected in both cohorts on follow-up were all stage IA, a greater fraction of melanomas were in situ
(7/12 vs. 2/6, ) in patients monitored by TB photography. We might have expected to detect more melanomas with TB photography given its predicted capacity to detect melanomas arising de novo
and from clinically non-atypical nevi, although prescient removal of DN with severe dysplasia (eight lesions) on follow-up visits could have decreased the detection rate since some of these lesions may have progressed to melanoma and been detected later.
Although not a primary motivator for changing our monitoring approach, we had found serial DELM photography to be very cumbersome given the time required (up to 45 min) to photograph numerous atypical nevi on the initial and (every) follow-up visit. While most patients required 30-50 min at each visit for clinical examination and photography or photographic comparison, we found that with TB photography the photographs could be obtained in 15 min such that the initial visit required 20-30 min and follow-up visits only 10-20 min (). Thus TB photography was more time-efficient, and may have accounted for a higher follow-up compliance rate than we observed in our prior study.14
In evaluating the role of photography on the physician's decision to biopsy, we acknowledge the influence of several potential confounding factors. These include patient concern, which motivated biopsies in cases where there was no photographic change, and patient age and lesion morphology, which played a significant role in the decision to biopsy new lesions. In comparing our two cohorts, it is worth noting that patient concern also likely played a role in the prior study in which a similar patient population was monitored by the same physicians operating in the same medicolegal environment. Of 168 lesions biopsied as a result of photographic comparison, however, patient concern was only noted in 27 (16%), thus TB photography identified many new and changing lesions that patients were unaware of. Photographic change may be more reliable than patient history, as the melanoma detection rate was 3/141 (2.1%) for lesions biopsied in which there was photographic change but no patient concern, and 0/56 (0%) for lesions biopsied solely because of patient concern.
We recognize that these two photographic approaches have inherent limitations that may bias which lesions are selected for biopsy. While serial DELM photography is highly sensitive for detecting changes in nevi over time, this approach is necessarily limited to detecting changes in a subset of pre-existing nevi and cannot detect new lesions. On the other hand, TB photography is geared towards detecting new lesions and its capacity to detect changing lesions is necessarily limited by the resolution of the photographs. Given these considerations, we might have expected a greater proportion of melanomas detected by DELM monitoring to be nevus-derived and a greater fraction of those detected by TB photography to present as new lesions. In both cohorts however, we found that a similarly small fraction of the melanomas (25% vs. 17%) detected on follow-up were nevus-derived, with the majority arising as de novo
lesions (). Our findings are consistent with other monitoring studies3, 5
and histologic studies,27-29
suggesting that most melanomas arise de novo
rather than from pre-existing nevi. Given this tendency of melanoma origin, one would predict that TB photography is better suited than serial DELM as a solitary strategy for early melanoma detection. Such would be particularly true for older patients with fewer nevi in whom melanoma would be more likely to present as a new lesion rather than as a changing nevus. Serial DELM, however, may be better suited for young individuals with a few clinically atypical nevi who will likely develop many new lesions, making it difficult to establish a baseline using TB photography. Thus a combined approach, in which selected regional photographs are used along with DELM monitoring, or in which DELM photographs of a subset of the most clinically atypical nevi are taken in patients monitored by TB photography, is probably optimal. However, incorporating two photographic systems will not be feasible for most practitioners. When we switched from serial DELM monitoring to TB photography five years ago, our hope was that the photographs would be of sufficient resolution to detect clinically significant changes. While it is possible that DELM monitoring could have detected some of the melanomas earlier, most (4/5) invasive melanomas we detected on follow-up were not nevus-derived. Thus DELM monitoring may only have resulted in earlier detection of these lesions if photography was performed after
the melanomas developed. In these cases of invasive melanoma detected on follow-up, the most important factor associated with delayed diagnosis was increased amount of time since the previous visit (1.5 years for one patient, 3 years for two patients). Therefore, as with any planned medical intervention, patient compliance is always a significant limitation of efficacy.
In summary, we have had the unique opportunity to compare two conventional photographic approaches in a similar patient population at increased risk for melanoma. In our experience, monitoring by TB photography appears to have advantages over serial DELM photography: it is more time-efficient and associated with lower biopsy rates and higher melanoma detection rates. Its greatest limitation appears to be patient compliance with timely follow-up examinations.