Malignant pleural effusion (MPE) imposes a high burden on the healthcare system in the Asian Pacific region, as lung and breast cancer are the commonest cancers associated with malignant pleural effusion, as the two commonest cancers in the Asian Pacific region.

While indwelling pleural catheter (IPC), a catheter that is inserted for long-term drainage of pleural fluid, is not commonly used in Asian countries, small-bore chest tubes are increasingly used due to their ease of insertion and causing less pain.

Injecting talc, a chemocal, to promote adhesion of pleura, called talc pleurodesis was an effective method of managing MPE. However, the optimal size of small-bore chest tubes and the feasibility of talc pleurodesis have not been thoroughly investigated.

This randomised controlled trial aims to evaluate the feasibility and success rate of pleurodesis using small-bore chest drains and to examine the outcomes associated with different sizes of these drains, namely 8 Fr, 12 Fr, and 14 Fr, in managing MPE.

The primary outcome is the feasibility of talc pleurodesis with different small-bore chest tubes. Secondary outcomes include the differences in recurrence rates post-pleurodesis between small-bore and ultra-small-bore chest tubes, as well as patient outcomes such as pain scores, SpO2/FiO2 ratios (oxygen saturation/fractional inspired oxygen ratio), and complications.

The sample size will be 60, and the project will be carried out over one year.

The outcome of this study can serve as a reference for managing MPE regarding the feasibility, safety, and efficacy of ultra-small-bore chest tubes worldwide, particularly in the Asia-Pacific region, where IPC is less common.

Chest tubes can be classified as large bore or small-bore base on the size, with commonly ≤14 French (Fr) was defined as small-bore and >14 Fr was defined as large bore. Small-bore chest tubes are increasingly used in malignant pleural effusion (MPE) since it is easier to insert and was reported to have less pain while insertion and in place. However, there is limited evidence and guideline on the use of small-bore chest tube. The size of chest tube for optimal drainage was not mentioned in the British Thoracic Society (BTS) guideline for pleural disease.

Pleurodesis is indicated for MPE or secondary pneumothorax to reduce the recurrent way, and can be performed in surgical or chemical. Different agents are available for chemical pleurodesis, namely talc, minocycline or blood patch. For MPE, talc slurry was shown to be non-inferior than talc poudrage for pleurodesis successful rate, and was shown to be superior than other sclerosant in chemical pleurodesis. For secondary spontaneous pneumothorax, chemical pleurodesis is performed when patient is not a surgical candidate or according to patient's preference. Chemical pleurodesis with talc slurry was shown to have higher efficacy and lower recurrence rate of pneumothorax compared with doxycycline in Asian population.

From the BTS clinical statement on pleural procedures, meta-analyses of studies on different chest tube size for pleurodesis show similar risks of procedure failure with large and small-bore tubes. However, limited evidence was available. The only randomised control trial with adequate sample size found small-bore chest tube was non inferior to large bore chest tube in terms of pleurodesis efficacy. There was a report of use of small-bore chest tube with size 10Fr in MPE, showing response rate of 84.2% post pleurodesis.

The definition of pleurodesis failure in MPE varies. Definition commonly used in previous studies define pleurodesis failure as pleural fluid recurrence in ipsilateral hemithorax requiring further therapeutic pleural intervention, with radiological evidence including chest x-ray (CXR), computed tomography (CT) scan of thorax or transthoracic ultrasound demonstrated same fluid recurrence upon follow up. Partial response was defined as localise effusion that does not progress, cause symptoms or require drainage.

In current practice for chest tube insertion by respiratory team in Queen Mary Hospital, chest tubes with pigtail or seldinger technique are available in size of 8Fr, 12Fr, 14Fr and 18Fr for drainage of pleural effusion or pneumothorax. Pleurodesis, commonly by talc, is performed through chest tubes when clinically indicated.

In this study, we hypothesize that the use of small bore and ultra small bore chest tubes are both effective in managing pleural effusion.

This is a prospective randomised controlled study for patients with MPE who require chest tube insertion. Eligible patients will be randomised into 1:1:1 ratio on 8Fr, 12 Fr or 14 Fr size chest tube. The study will be conducted at Queen Mary Hospital, a tertiary and university-affiliated hospital in Hong Kong.

After study recruitment, chest drain with size according to randomization will be inserted. The baseline characteristics, namely age, sex, underlying malignancy, size of pleural effusion, the patient outcomes including pain score, oxygen saturation, complications including dislodgement, infection, hemothorax, blocked tube and mortality will be analysed between different groups.

For statistical analysis, univariant analysis will be performed first. For categorical factors, including recurrence of pleural effusion or pneumothorax in different groups, Fisher exact test will be performed. Odd ratios will be calculated. Unpaired data on two samples will be performed by Wilcoxon rank sum test. Multivariant logistic regression will then be performed on the effect of different factors on the outcomes. P < 0.05 was taken as statistically significant.

Inclusion Criteria:

• Pleural effusion.
• With clinical indications for pleural drainage and chest drain insertion.
• With anticipated need for pleurodesis e.g. known malignancy, no clinical signs of pleural infection.
• age ≥18 year-old

Exclusion Criteria:

• Pleural effusion not sizable for drainage.
• With clinical suspicion of pleural infection e.g. pleuritic chest pain, fever, ultrasound showed loculated pleural effusion
• Age ≤18 year-old

According to the current ethics approval protocol, the IPD will be stored anonymously and destroyed 3 years after completion of study.