Full Title: Prevention of Malignant Seeding at Drain Sites after Invasive Procedures (Surgery and/or Thoracoscopy) by Hypofractionated Radiotherapy in Patients with Pleural Mesothelioma

Source: Acta Oncologica

Radiotherapy is not a general modality in the treatment of mesothelioma because the diffuse nature of the disease’s invasion pattern rarely presents a localized malignancy for the radiation to be applied to. Due to mesothelioma's widespread appearance, the radiation would have to be delivered over a very wide area at very high doses to be effective, but this would put vital organs such as the lungs, heart and kidneys at serious risk for radiation overexposure and sickness. There is, however, a very specific use of radiotherapy that has shown some efficacy in the treatment of pleural mesothelioma and peritoneal mesothelioma: localized application of radiation to drain sites and other instrumentation sites after treatment, or other medical intervention.

Metastases to areas of surgical intervention are a common problem in the treatment of a number of different cancers, but the problem seems especially acute with mesothelioma treatments. Different studies have reported different figures on the likelihood of this occurring, but most estimates report a 20-50% of chance of surgical site metastases following treatment. Prior studies have reported on the benefits of radiotherapy to prevent tumor seeding, but the treatment is still not deployed in many cases and research into this question continues on a number of fronts.

An article has recently been published in the journal Acta Oncologica that describes the results of a study conducted by Italian physicians on their use of radiation to prevent drain site metastases. That article will be summarized in the following sections.

Overview of the Study

To investigate the efficacy of radiation therapy for the prevention of tract site metastases in patients treated for pleural mesothelioma, the authors enrolled 32 patients with histologically-confirmed mesothelioma into their study. There were 24 men and 8 women, with the average age at diagnosis listed at 64 years-old. 25 patients presented with epithelial mesothelioma, 6 with sarcomatoid mesothelioma and there was 1 case of the biphasic subtype. When the patient cohort was analyzed by stage at time of diagnosis, the authors found that 2 patients were considered Stage IA, 3 patients were considered Stage IB, 20 patients were listed as Stage II, 4 presented as Stage III and 3 others as Stage IV.

The patients underwent a variety of procedures in their diagnosis and treatment: some were palliative in their intent, while others were curative, but all involved some type of surgical intervention, from the insertion of drainage tubes to radical pleurectomy to other procedures as well. After their wounds healed from the original operations, all of the patients then received radiation therapy to each area that was treated by the procedure. 21Gy were delivered in three daily fractions to each patient. After the completion of treatment, 20 patients received some form of chemotherapy.

Patients received clinical examinations every 3-4 months during the first two years of treatment and then at 6-8 months following the initial two-year period.

Results

The authors were quite pleased with the results of their study. They report that “after a mean follow-up of 13.6 months...from the end of radiation therapy, no patient developed subcutaneous nodules in the treated area.” They also report that the therapy was well tolerated, with 11 patients developing a temporary grade I erythema, which is a reddening and swelling of the skin, but seemingly nothing more serious and no late treatment effects were seen.

The one year survival for the patient cohort was reported as 68.9% and the two-year rate was reported as 30.3%—both of which are excellent results for pleural mesothelioma patients. 17 patients (52%) died of mesothelioma due to local progression after a mean survival of 12.6 months. The authors note that 13 patients (41%) are still alive after a 13.9 month mean follow-up and two others are alive “without evidence of disease after a mean follow-up of 16.5 months.”

Conclusion

Because of the results of their study, the authors conclude that radiotherapy following therapeutic treatment of pleural mesothelioma is an effective methodology to prevent tumor seeding in areas of surgical intervention. They note that although this procedure has not yet been incorporated into standard treatment protocols, their results, as well as the results of a number of other studies, demonstrate radiation therapy’s benefits for the treatment of mesothelioma and they propose that it be deployed as a standard therapy.

Labels: mesothelioma, pleuralmesothelioma, radiation, treatments