Patients with stage I and stage II melanoma have a five-year survival rate that approaches 80 percent. Since the other 20 percent of patients have occult distant metastases, initial staging evaluations are often performed, although outcome data in asymptomatic patients are lacking. The most commonly performed procedure following a diagnosis of localized melanoma is chest radiography, because the lung is the most common visceral site for metastases. Terhune and associates retrospectively reviewed the medical records of consecutive asymptomatic patients with localized melanoma to assess the usefulness of an initial staging chest radiograph.
A total of 876 out of 1,032 patients (85 percent) in the study group had undergone an initial staging chest radiograph. Most of the tumors were of the superficial spreading type and occurred on the trunk. Only 5 percent could not be staged because the depth of invasion extended to the deep margins following a shave biopsy or because of misorientation of the biopsy specimen. Five percent of the biopsy samples revealed melanoma in situ, 62 percent showed stage I disease, 25 percent showed stage II disease of less than 4 mm and 5 percent showed stage II disease of 4 mm or more.
A total of 130 patients (15 percent) had a suspicious finding on chest radiograph necessitating further evaluation such as a repeat chest radiograph or a computed tomographic (CT) scan of the chest. In 35 patients, a combination of these modes was required to confirm the diagnosis. A total of 128 patients had no evidence of lung metastases. Only one patient underwent additional studies that suggested the presence of metastases. Subsequent histology revealed metastatic melanoma.
Silent pulmonary metastasis was found in only one patient. No metastatic lung disease was detected in cases of melanoma in situ and stage I disease, while lung metastasis was found in one of 258 patients with stage II disease. The frequency of false-positive results was 15 percent. Of the group for whom long-term follow-up data were available, 30 patients developed lung metastases and two developed a primary lung cancer. Seventeen cases of lung metastases occurred in patients with initial negative findings on chest radiograph, and five occurred in patients with initial suspicious findings on chest radiograph. This suggests that lung metastases occur more frequently in patients with suspicious false-positive radiographs. The authors suggest that these metastases were probably present at initial diagnosis and were not detected because of the limitations of chest radiography.
The authors conclude that initial chest radiographic screening in asymptomatic patients with stage I and intermediate-thickness stage II melanoma is highly unlikely to detect silent pulmonary metastases. In addition, the high false-positive rate can lead to costly subsequent investigations. The authors stress the importance of a thorough medical history and physical examination in the initial assessment of patients with cutaneous melanoma.