An improved method of delivering a sclerosing agent for the treatment of malignant pleural effusion

Beyond diagnosis: a narrative review of the evolving therapeutic role of medical thoracoscopy in the management of pleural diseases

Background and Objective

Medical thoracoscopy (MT) is an endoscopic technique performed by interventional pulmonologists with a favorable safety profile and few contraindications, providing diagnostic and therapeutic intervention in a single sitting. This narrative review was designed to summarize the therapeutic role of MT based on the latest results from the available literature.

Methods

Pertinent literature published in English, relative to human studies, between 2010-2022 was searched in Medline/PubMed and Cochrane databases. Publications regarded as relevant were considered for inclusion in this review; additional references were added based on the authors' knowledge and judgment. The review considered population studies, meta-analyses, case series, and case reports.

Key Content and Findings

MT has mostly been described and is currently used globally in the diagnostic approach to exudative pleural effusion of undetermined origin. Carefully evaluating the literature, it is clear that there is initial evidence to support the use of MT in the therapeutic approach of malignant pleural effusion, pneumothorax, empyema, and less frequently hemothorax and foreign body retrieval.

Conclusions

MT is an effective procedure for treating the clinical entities presented in this document; it must be carried out in selected patients, managed in centers with high procedural expertise. Further evidence is needed to assess the optimal indications and appropriate patients' profiles for therapeutic MT. The endpoints of length of hospital stay, surgical referral, complications and mortality will have to be considered in future studies to validate it as a therapeutic intervention to be applied globally.

A mechanism for improved talc pleurodesis via foam delivery

Talcum powder is recognized as the leading drug for pleurodesis, a treatment of choice for malignant pleural effusions. Recently, it was shown that hydrogel foam delivery systems significantly enhanced the number of adhesions between the chest wall and the lung in a New Zealand rabbit model due to the sol-gel transition. However, many questions still remain regarding the cause of improved efficacy, such as: (1) Would only hydrogel foams improve the efficacy of talc pleurodesis? (2) Is it possible to achieve the same efficacy of hydrogels using non-hydrogel foams? 3) What are the physicochemical properties that can be correlated to the efficacy of talc pleurodesis? In this study, we use non-hydrogel foam formulations to determine the efficacy of pleurodesis. Foam stability and rheology of the formulations were correlated to adhesion formation. The results clearly suggest a correlation of pleurodesis efficacy to the viscosity and modulus of the foam delivery system.

The efficacy of hydrogel foams in talc Pleurodesis

BACKGROUND

Malignant pleural effusions are a serious complication of many late stage cancers that adversely affect quality of life. Pleurodesis with talc slurry is a standard treatment option, but clinical failures occur, possible due to poor talc delivery. A novel drug-delivery system was developed that fills the entire thoracic cavity with a liquid foam containing talc. The foam is designed to gel and adhere to the tissue walls at body temperature, to improve talc deposition and efficacy.

METHODS

Rheology, foam stability, and ex-vivo coating and bio-adhesion studies were performed on three concentrations of a novel hydrogel talc foam system that was developed to improve delivery of talc to the pleural surfaces. A New Zealand rabbit model of pleurodesis was used to evaluate effectiveness of the foams at inducing adhesion formation and compared to talc slurry. The rabbits were recovered after they had one of the test agents instilled into their pleura, and then sacrificed after 28 days. Pleurodesis was assessed by a blinded pathologist using a standardized pathological scoring system.

RESULTS

All talc foam formulations produced foams that gelled at physiological temperatures and were relatively stable for at least two hours. As the concentration of the formulation increased the gelation temperature decreased and the foam adhesiveness increased. Rabbits that received talc foam had significantly greater adhesion formation than talc slurry (mean score of 2.21 vs. 1.18 (p < 0.05)). Rabbits that received the 20% foam developed the most adhesions.

CONCLUSIONS

This study demonstrates that our triblock copolymer hydrogel foam delivery system enhances adhesion formation in an experimental model. This novel approach can have important clinical impact, potentially improving efficacy of existing therapies and reducing the need for more invasive treatments.