Dermatoscopy versus loupe magnification for determination of surgical margins during Modified Mohs*surgery of facial basal cell carcinoma

Basal cell carcinoma (BCC) is the most commonly diagnosed skin cancer. It is
known that BCC is a locally invasive malignant skin tumour with a high local
tissue morbidity due to infiltration and destruction of adjacent tissues.
Incidence rates vary from 788:100.000 people annually in Australia to
146:100.000 people annually in the United States. Despite the high incidence,
metastasis of this tumour is rare. Estimates of metastasis incidence vary
widely, ranging from 0.0028% to 0.55% of all BCCs.
The choice of treatment depends on multiple factors: tumour type, biological
behaviour, size, location, physical condition and preference of the patient,
local expertise and costs. Surgical excision with conventional margins is the
most common and effective treatment. The goal of treatment is complete and
radical removal of the tumour cells without loss of healthy tissue and with a
low recurrence rate. The Dutch Guideline on BCC*s recommends conventional
surgical excision with a clinical margin of 3 mm for a BCC * 10mm. For larger
tumours and/or infiltrative BCC or for a recurrent BCC a margin of 5 mm is
recommended. Visual magnifying tools for determination of the surgical margin
are not discussed in the guideline.

After surgical excision, the margins of the BCC is examined for the presence of
tumour cells. The gold standard for examination is using formalin-fixed
paraffin embedded (FFPE) coupes. The definitive outcome of this FFPE procedure
is known a few days after surgery. In case of incomplete excision a re-excision
is then necessary and unfortunately, the reconstruction necessary to close the
defect after the first excision has to be destructed. To prevent this situation
the margins can be examined intraoperative. Two effective techniques for
intra-operative margin control are Mohs* micrographic surgery (MMS) and frozen
section controlled excision. The Medical Centre Leeuwarden, the Netherlands,
performs Modified Mohs* surgery, or *bread loaf* frozen section controlled
excision technique. Modified Mohs* is used in our centre when a BCC has an
infiltrative character or when a primary reconstruction with a transposition-
or rotationflap is needed.

Different studies describe high percentages (16-65%) of irradical excisions in
patients with a facial BCC.These result underline the need for improvement to
obtain a higher percentage of one stage radical excisions. A possible solution
might be precise definition of the surgical margins of the BCC with a
magnifying device, such as a dermatoscope. Multiple studies have evaluated the
use of a dermatoscope for determination of the surgical margins. Caresane et
al. described a 98.5% direct radical excision in 200 patients with a facial
BCC. Surgical margins were detected with visual inspection and checked with a
dermatoscope and excision margins of 2mm were used. In 14 (7%) cases the lesion
appeared larger than when evaluated clinically. Although this in not a
(randomised) controlled trial it points out the possible advantage of the
dermatoscope. In the prospective, non-randomised study of Carducci et al., in
112 patients with a facial BCC the surgical margin of 3 mm was determined using
a dermatoscope and showed in 93% optimal direct radical excisions compared to
78% when using visual inspection (p<0,026) There are also studies in which no
advantage of the use of the dermatoscope has been found. Four studies
investigated MMS versus MMS in combination with dermatoscopy for determination
of the surgical margins. None of these studies found significant differences in
the amount of MMS stages between treatment groups. The biggest limitation off
these studies is the sample size, the largest group contained 23 patients.In
conclusion, we do not know yet whether the use of a dermatoscope will improve
one stage radical excision in facial BCC*s.

The aim of our study is to compare the use of the dermatoscope to loupe
magnification for determination surgical margins of facial BCC*s within a
randomised controlled trial.

The aim of this study is to evaluate the proportion of patients with a radical
excision after the first excision using the dermatoscope for evaluating the
peripheral borders compared to loupe magnification.
Secondary parameters will be the influence of the dermatoscoop on total time
and costs of the procedure, scar quality (POSAS) and postoperative
complications (bleeding, infection, wound dehiscence). Also the histological
types of BCC and exact histological margin will be documented en evaluated.

Aims:
Does the use of a dermatoscope for determination of surgical margins in
patients with facial BCC increase the percentage of one stage radical excisions
compared to determination of the surgical margins using loupe magnification

Method
The intervention group wil contain patients with facial BCC treated with
modified Mohs* using dermatoscopy for demarcation of surgical margins, versus
the control group patients with facial BCC treated with modified Mohs* using
loupe magnification for demarcation of surgical margins

Design
Randomised controlled trial

Hypothesis:
The use of dermatoscopy for demarcation of surgical margins will increase the
proportion of one stage radical excisions.

Randomisation
Patients are randomly allocated to the group *dermatoscopy for determination of
surgical margins* or *control group (loupe magnification for determination of
surgical margins*. A randomisation list is prepared, using a random number
table. The allocation sequence is concealed by using sequentially numbered,
opaque sealed envelopes (SNOSE) prepared by the coordinating researcher which
are opened at day of surgery after having obtained informed consent

Sample size:
In order to achieve at least 80% power to detect a difference between the group
proportions of 15% (78% under the null hypothesis and 93% under the alternative
hypothesis), a sample size of 2x94 patients is required. The test statistic
used is the two-sided Fisher's Exact test . The significance level of the test
was targeted at 0.05

In the control group loupe magnification will be used for evaluation of the
margins. In the intervention group the dermatoscope is used for evaluation of
the margins .

No clear risks are described with the use of a dermatoscope. The extra
information about the study at the first consult will approximately take a few
minutes. Since we expect a higher percentage of one stage radical excisions the
procedure might take less time.