ORLANDO, Fla.—Surgery should be considered an option for patients with slow-growing thymomas that have extended into the pleural cavity, providing a safe treatment with long-term cancer control. That was the conclusion of a poster study reported here by Japanese researchers at the Society of Thoracic Surgeons Annual Meeting.
After five years, patients who underwent the surgery had a 92 percent survival rate, and a third of the patients were free of disease, said Tomohiro Murakawa, MD, Assistant Professor of Thoracic Surgery at the University of Tokyo.
“Our retrospective study may indicate that resection of pleural dissemination from advanced thymoma may play a role for local control of the disease in the context of a multimodality approach,” he said in an interview. “Even though it is not R0 resection, this surgery should be considered a favorable choice of treatment.”
Murakawa and his colleagues reviewed the outcomes of 136 patients with thymoma who underwent surgery from 1991 to 2012—the 21-year interval attesting to the rarity of the tumor, he noted. Of the 13 consecutive patients in whom the thymoma had invaded the pleural cavity and who underwent resection of visual tumor nodules, seven had synchronous tumors and six had metachronous tumors.
Five of the seven patients with synchronous tumors underwent resection of the disseminated nodules —including one patient who had 52 nodules resected. That 27-year-old woman later had the disease recur in the pleura and was operated on a second time, but is now tumor free, Murakawa reported.
All seven of the patients remain alive, but four have a tumor burden: A 34-year-old woman who was treated with more extensive extrapleural pneumonectomy underwent three re-resections for recurrence in the pleura but is now tumor free. A 49-year-old man who underwent extrapleural pneumonectomy had pleura recurrence as well remains alive but still has residual tumor burden. A 78-year-old woman experienced pleura recurrence and was treated with radiation. She is one of the surviving patients but has residual tumor burden.
All six of the patients diagnosed with metachronous thymoma tumors underwent resection of disseminated nodules, Murakawa continued. The surgeons removed one to 21 of these nodules. Two women in their 50s had one and two nodules removed, and the patients remain alive without evidence of tumors. A 61-year-old woman who underwent resection of disseminated nodules died due to postoperative bleeding. She was the only fatality in the series.
“The optimal strategy for pleural dissemination of advanced thymoma remains controversial,” he said, adding that other reports suggest a potential benefit from macroscopic clearance of dissemination.
Murakawa noted that while the number of patients in the study is small, all the recent studies in the medical literature dealing with surgical resection of dissemination of thymoma have only a few patients. The largest study was reported in 2009 and included 21 patients, who had a five-year overall survival rate of 73 percent and a five-year tumor-free survival rate of 13 percent. In a smaller study in 2011 of seven patients who underwent extrapleural pneumonectomy for disseminated thymoma, all remain alive, although none as yet for five years.
Thymoma originates from the epithelial cells of the thymus, and although an uncommon tumor, is associated with the neuromuscular disorder myasthenia gravis and other autoimmune disorders, he noted. Metastases of thymoma are considered rare. In the study he reported, there were no metastases, although, again, because of the relatively short duration of follow-up—median of 2.6 years—the chance of the disease metastasizing was diminished.
‘Continue to Follow’
Asked for his perspective, Andrew Chang, MD, Chief of the Thoracic Surgery Section at the University of Michigan, noted that thymoma is very slow growing and that there are no nerves in the chest that can be an indication that such a mass is growing. “It is usually picked up by a random scanning study, and when picked up late, sometimes there is already spread to the chest.
“The debate with any tumor that has already spread outside where its primary home is: Does it make sense to put that patient through an operation—i.e., by doing this procedure, would we be extending the person's life or are we going to put them through an unnecessary procedure? Thymoma is a little different situation because it is a lot slower growing than other cancers. There are various ways to approach surgical resection of thymoma: you can go through the chest as in a standard heart operation, you can go through the side.
“In this study, the surgeons either removed the nodules or—in a couple of cases—took out the entire lung,” Chang continued. “The latter is a very aggressive approach but if you look at how the patients do afterwards, overall they appear to have done okay. They have done well with this approach, and there was just one death associated with this surgery.”
He said that while several patients have residual tumor, the slow-growing nature of thymoma would generally mean that the tumor-burdened survival is not severely impacting the patients' quality of life.
Some of the patients have been followed out to 10 years, which Chang said was important to study in a tumor such as thymoma. He noted that recurrence appeared to happen within three years of surgery. “All the recurrences in this series of patients occurred in the chest,” he said. “You are not seeing disease spread to other parts of the body.”
“It is important for these researchers to follow these patients for several more years,” he said. “This is a preliminary report. In our group we do operations like this, but it depends on the patients whether you want to do this procedure.”