Prophylactic radiotherapy to prevent procedure-tract metastases

Is there a role for prophylactic radiotherapy to intervention tract sites in patients with malignant pleural mesothelioma?

Malignant pleural mesothelioma has a high morbidity and poor prognosis. Most patients undergo invasive pleural interventions to either facilitate diagnosis and/or alleviate symptoms from malignant pleural effusion. Procedure tract metastasis (PTM) are a well-known complication of pleural procedures in mesothelioma and there has been longstanding debate regarding the role of prophylactic irradiation of tracts in preventing them. This review summarises the existing evidence surrounding this controversial topic. Despite initial discrepancies amongst the results of 3 small, historical trials regarding the efficacy of prophylactic radiotherapy in mesothelioma, two large randomised-control trials have recently provided more clarity. The SMART trial, which randomised over 200 patients, found no benefit of prophylactic radiotherapy in reducing PTM incidence in their primary analysis, with a number needed to treat (NNT) of 25.1 to prevent a single painful PTM. Additionally, there was no benefit in terms of symptomology, health-related quality of life parameters or cost-effectiveness. This is supported by the preliminary results of the Prophylactic Irradiation of Tracts in Patients with Pleural Mesothelioma (PIT) trial, which randomised 375 patients and also found no evidence that prophylactic radiotherapy reduced PTM incidence, although the full results are still awaited. Combined analysis of these trials is planned, which will help clarify whether specific subpopulations may derive benefit from prophylactic radiotherapy, such as patients not receiving chemotherapy. Based on the currently available evidence there is no role for routine delivery of prophylactic radiotherapy to prevent PTM in mesothelioma. Instead holistic and vigilant follow-up of patients is recommended, aiming for adequate palliation of symptoms and support for patients. Should painful nodules develop these can be effectively treated with subsequent palliative radiotherapy. After years of uncertainty and debate, recent international guidelines have consistently advised against the use of prophylactic irradiation of tracts based on contemporary high-quality evidence.

Prophylactic radiotherapy for procedure tract metastases in mesothelioma: a review

PURPOSE OF REVIEW

Malignant pleural mesothelioma is an aggressive malignancy with a very poor prognosis. The majority of patients require pleural procedures for diagnostic or fluid management purposes. Damage to the pleura during these procedures can lead to procedure tract metastases (PTMs), with increasing risk from larger interventions. Prophylactic radiotherapy to these sites is a controversial topic with conflicting results from trial data. In this review, we summarize the recent evidence.

RECENT FINDINGS

Four RCTs have been published on this topic, with another in follow-up. The earliest, from a cohort of 40 patients, strongly advocated the use of prophylactic radiotherapy. More recent trials, most notably the Surgical and large bore procedures in Malignant pleural mesothelioma And Radiotherapy Trial (SMART) (which randomized over 200 patients) did not demonstrate any benefit, especially when patient report symptoms and cost-effectiveness are considered. Certain subgroups demand further investigation, such as those not receiving systematic chemotherapy or with surgical intervention sites. The soon to be published Prophylactic Irradiation of Tracts (PIT) trial may help to further clarify best practice.

SUMMARY

Recent studies have shown that prophylactic radiotherapy should not be routinely used to prevent PTMs in mesothelioma. Instead patients should undergo careful clinical follow-up to ensure PTMs are identified and treated promptly to minimize symptoms.