Pure mediastinal seminomas are curable in the large majority of patients, even when metastatic at the time of diagnosis. These tumors are highly sensitive to radiation therapy and to combination chemotherapy, and selection of treatment therefore depends on disease stage and size of mediastinal tumor.
Approximately 20% of mediastinal seminomas are diagnosed after a chest radiograph reveals an asymptomatic anterior mediastinal mass. Some of these patients have relatively small tumors, and a complete surgical resection can be easily accomplished at the time of surgical biopsy for diagnosis. Although surgical resection alone is curative in some of these patients, a course of postoperative radiation therapy to the mediastinum should always be administered in order to prevent local recurrence. Because other highly effective treatment modalities exist, extensive surgical procedures for resection or debulking of large mediastinal seminomas are contraindicated.
The large majority of patients with medias-tinal seminoma (at least 80%) are not candidates for surgical resection because of the large size of the mediastinal primary tumor or the presence of distant metastases. Pure mediastinal semi-nomas share the exquisite radiosensitivity of testicular seminoma, and primary radiotherapy is often curative in these tumors. Although most reported series are relatively small, approximately 60% of patients achieve long-term disease-free survival following mediastinal irradiation. Most treatment failures are a result of the appearance of distant metastases, rather than a result of inadequate local tumor control. The majority of patients who relapse after radiation therapy can be salvaged with subsequent chemotherapy.
Highly effective systemic combination chemotherapy now offers the best option for curative treatment of patients with mediastinal seminoma. When used in advanced testicular seminoma, intensive cisplatin-based regimens are at least as active as they are against nonseminomatous germ cell tumors.
Table 96-1summarizes the experience with modern cisplatin-based combination regimens in the treatment of pure mediastinal seminoma. Even with bulky local tumors and frequent metastatic disease, all recent series have shown cure rates of > 80% with initial cisplatin-based chemotherapy.
Patients with bulky seminoma at any site frequently have residual radiographic abnormalities after chemotherapy. In most patients, these masses represent dense scirrhous reactions rather than viable seminoma or benign teratoma. Because of the dense fibrosis, retroperitoneal node dissection in such patients is difficult, is frequently incomplete, and can be associated with high mortality. When residual lesions are less than 3 cm in maximum diameter, residual active tumor is rare, and patients should be followed with serial chest CT scans. Residual seminoma becomes more frequent when residual masses are > 3 cm, and biopsy should be considered. If immediate biopsy is not performed, these patients should be monitored very closely (ie, CT scans every 2 months during the first year), with early biopsy of any enlarging mass on chest radiograph or chest CT.
In summary, most patients with mediastinal seminoma can be cured with therapy, and all patients should be approached with this intent. Patients with small tumors (usually asymptomatic) that appear resectable should undergo thoracotomy and attempted complete resection. Radical debulking procedures for patients with larger tumors are not indicated. In the subset of patients who undergo complete excision, postoperative radiotherapy (4,000 to 4,500 cGy) is curative in almost all patients and is the treatment of choice. All other patients should receive initial cisplatin-based chemotherapy, unless they have a specific medical contraindication to such therapy. In such patients with localized tumors in the mediastinum, radiation therapy is an acceptable alternative. Optimal chemotherapy includes four courses of bleomycin, etoposide, and cisplatin, as is recommended for poor-prognosis testicular germ cell tumors.
Revision date: June 14, 2011
Last revised: by Andrew G. Epstein, M.D.