Are malignant melanoma patients at higher risk for a second cancer?

This study tests whether malignant melanoma (MM) patients are at higher risk of having an unrelated second cancer by comparing the observed incidence of a second cancer in a given population of MM patients with the expected number in an age-matched and sex-matched group of healthy people followed for a similar period. The analysis was based on the person-years method in which the main consideration is the follow-up period after the diagnosis of MM. Of 370 patients with histologically confirmed MM, 27 (7.3%) had a second noncutaneous invasive cancer, diagnosed either simultaneously (within 6 months, five patients) or after the diagnosis of MM (22 patients). The follow-up period for the entire MM group was 1253 person-years, a period during which the expected number of cancer cases in the normal population, according to the Israel Cancer Registry, was 6.6. The observed-expected ratio or the relative risk (RR) was 4.1 (P less than 0.01). After excluding the five patients with simultaneous diagnosis of MM and a second cancer, analysis of the remaining 22 patients in whom MM definitely preceded the second cancer showed an RR of 3.3 (P less than 0.01). For the entire group, there were nine patients with breast cancer, five with head and neck cancer (two with thyroid and three with oral cavity cancer), five with gynecologic cancer (one with uterine and four with ovarian cancer), five myeloproliferative malignancies (one with lymphoma, three with chronic lymphocytic leukemia, and one with myeloma), three gastrointestinal carcinomas (two with colon and one with stomach cancer), and two soft tissue sarcomas. When the differential analysis according to gender and age was done, it was found that the RR was higher for women (5.5, P less than 0.01) than for men where the RR was 2.2 (P less than 0.05). Differential analysis for various age groups showed that the trend for second cancer was consistent in all age groups, with a slight increase in the younger ones. None of the variables of MM, such as location of the primary tumor, level of invasion, or stage, were predictive for a second cancer. Furthermore, the RR for a second cancer did not relate significantly with the treatment given to the MM patient. Concerning the type of second cancer, it was found that the RR was especially high for breast cancer--6.6. These data indicate that MM patients may be at higher risk for having a noncutaneous invasive cancer compared with the general population.