A practical decision-tree model to predict complexity of reconstructive surgery after periocular basal cell carcinoma excision

A representation and interpretation of the area under a receiver operating characteristic (ROC) curve obtained by the "rating" method, or by mathematical predictions based on patient characteristics, is presented. It is shown that in such a setting the area represents the probability that a randomly chosen diseased subject is (correctly) rated or ranked with greater suspicion than a randomly chosen non-diseased subject. Moreover, this probability of a correct ranking is the same quantity that is estimated by the already well-studied nonparametric Wilcoxon statistic. These two relationships are exploited to (a) provide rapid closed-form expressions for the approximate magnitude of the sampling variability, i.e., standard error that one uses to accompany the area under a smoothed ROC curve, (b) guide in determining the size of the sample required to provide a sufficiently reliable estimate of this area, and (c) determine how large sample sizes should be to ensure that one can statistically detect differences in the accuracy of diagnostic techniques.

Basal cell carcinoma (BCC) is the most common cancer worldwide in white-skinned populations. Recent studies suggest that BCC is not a single entity and that different histological subtypes show different clinical behaviour and might have different aetiology. To provide information on the incidence of BCC by histopathological subtype and body site. A case series of BCC from a prospective population-based register study collecting information on all excised and histologically confirmed skin cancers in Townsville, north Australia between 1997 and 1999. Age-standardized incidence rates for nodular BCC were 727.1 per 100 000 inhabitants per year for males and 411.8 for females, while rates for superficial BCC were 336.5 for males and 251.4 for females. Incidence rates for 'high risk' BCC were 261.3 for males, 146.5 for females with infiltrative, and 156.7 for males and 100.2 for females with micronodular types. Superficial BCC occurred at a younger age, particularly in female patients. For all histological subtypes and both genders relative tumour density was highest for the face, followed by the neck. An exception was superficial BCC in males, where the posterior trunk was second, followed by the neck. The study found a higher rate of superficial BCC than previous studies from less sun-exposed countries, and a more equal distribution of superficial BCC on face, trunk and limbs. These results seem to blur the difference between intermittent and continuous sun exposure as the causative environmental agents. The clinical implications of 'high risk' BCC rates are discussed.

Basal cell carcinomas (BCC) are among the most common cancers in white subjects. Etiologic factors include ultraviolet and ionizing radiation, chemical carcinogens, and possibly infection with human papillomaviruses. Because of clinical and histologic differences, differential pathogenetic mechanisms have been suggested for different BCC subtypes. We studied the patient and tumor characteristics of all BCC diagnosed and/or treated at the departments of Dermatology and Plastic Surgery of our hospital between 1985 and 1996, and a review of the literature was carried out. Some important differences between patients with nodular BCC and patients with superficial BCC were observed. The frequency of superficial BCC was higher in females and was seen in younger patients as compared with nodular BCC. The latter occurred mainly in the head/neck region: in males they were seen more frequently on the ears, and in females they were predominantly seen on the eyelids, the lips, and in the neck. Superficial BCC occurred mainly on the trunk, and occurred significantly more often on the trunk in males than in females, where the legs were the most common site. These findings strongly suggest that the superficial subtype is a separate group within the clinical entity of BCC. Furthermore, our findings seem to support the etiologic role of sun exposure in these tumors; however, this role may be different for each subtype. Chronic sun exposure may be an etiologic factor in nodular BCC as compared with intermittent sun exposure in superficial BCC. Other factors, such as differences in site specific host factors and referral bias, may also play a role in the differences found between the subtypes.