Evidence Supporting Radiation-Then-Surgery for Mesothelioma Grows

Evidence continues to accumulate suggesting that extrapleural pneumonectomy preceded by radiation therapy is a safe and effective treatment for appropriate malignant pleural mesothelioma patients.

The latest data showing this to be the case comes from researchers who spoke at the annual meeting of the American Association for Thoracic Surgery in Seattle.

The researchers — from Toronto General Hospital and Princess Margaret Hospital, both in Canada — told the attendees about the results of a phase II clinical trial they started in 2008 and concluded last year.

The trial involved 62 malignant pleural mesothelioma patients.

The use of radiation, followed by removal of one lung to treat mesothelioma, is controversial in some circles because it reverses the usual order in which these two procedures are performed.

It’s also controversial because radiation is administered in the span of just a week. In that time, patients receive the equivalent of over a month’s worth of hemithoracic intensity-modulated radiation.

Due to these unorthodoxies, researchers have been interested in verifying that this approach to treating mesothelioma is safe and effective.

Reduced Mesothelioma Recurrence Is One Goal

The researchers knew at the very start that there is one big, unavoidable side effect of giving high-dose radiation to mesothelioma patients.

The side effect is that patients afterward are in peril of developing radiation pneumonitis, a condition that usually leads to respiratory failure.

That’s why in this mesothelioma treatment strategy one of the lungs — the one that receives the radiation — is surgically removed 10 to 14 days later.

But taking out one of the lungs is the whole idea behind an extrapleural pneumonectomy anyway.
When one of the lungs becomes stippled with mesothelioma tumors, removing it is the surest way to purge the cancer.

However, eliminating the mesothelioma is not the only goal of the surgery. The second goal is to thwart its recurrence.

If radiation is given after the surgery — as is standard — it has to be of a low dose and spread out over time to minimize the risk of radiation pneumonitis.

The problem with that is the radiation isn’t strong enough to kill off whatever mesothelioma cells escaped the knife and remained behind. So, before long, mesothelioma tumors start up again.

In contrast, the high-dose radiation prior to surgery is more than sufficient to knock down everything in its path — mesothelioma cells, healthy cells, you name it.

Since the lung is slated to come out regardless, giving the radiation first makes a lot of sense, proponents argue.

An earlier study by the Toronto General Hospital and Princess Margaret Hospital researchers indicated that radiation-then-surgery more than doubled mesothelioma survival rates.

Epithelioid Mesothelioma Patients Gained Most

The phase II trial described at the thoracic surgery association’s annual meeting involved 10 patients diagnosed as having stage I mesothelioma, 35 with stage II, the remainder with stage III.

All of them received 25 Gy to 30 Gy of intensity-modulated radiation therapy in five daily fractions for one week. The radiation was delivered to each patient’s ipsilateral hemithorax.

During the trial, 61 of the 62 patients underwent subsequent surgical resection of the diaphragm. Most of them also underwent resection of the posterior pericardium and bronchial stump coverage.

Of these, 56 of the patients experienced overall mesothelioma survival in excess of 36 months. The best results were seen in mesothelioma patients with the epithelial type of cancer cells.

The researchers told the meeting attendees that more study is needed to before solid conclusions about the safety and efficacy of radiation therapy preceding extrapleural pneumonectomy can be drawn.

However, the researchers felt the outcome of their phase II study makes it clear that this mesothelioma treatment modality continues to show promise.