Prior to joining this study, you will have already received at least one but not more than two cycles of pembrolizumab at a dose of either 200 mg or 2 mg per kilogram of body weight, given through an intravenous infusion every 3 weeks. Alternatively, you may have received at least one but not more than one cycle of pembrolizumab at a dose of 400 mg or 4 mg per kilogram of body weight, given through an intravenous infusion every 6 we weeks.

This initial treatment is part of your first-line therapy for advanced lung cancer.

A blood sample will be collected to measure the level of ctDNA (circulating tumor DNA, which are small fragments of cancer DNA found in the bloodstream). This test is required to determine if you can proceed in the study.

Imaging scans, including a CT scan (a type of X-ray that creates detailed images of the inside of your body) of your chest, abdomen, and pelvis, will be performed within 14 days before you are assigned to a treatment group. If you have known brain metastases (cancer that has spread to the brain), an MRI or CT scan of the brain will also be done.

These scans are performed to ensure your disease has not progressed to a point that would require a change in your cancer treatment.

You must have detectable ctDNA in your blood sample to be assigned to a treatment group.

Based on your ctDNA level and other factors, you will be assigned to one of two treatment groups. This assignment will determine whether you continue receiving pembrolizumab alone or receive pembrolizumab combined with chemotherapy.

If assigned to this group, you will continue receiving pembrolizumab as a solution for infusion (a liquid medication given slowly into a vein over a period of time).

The dose and schedule will follow the same regimen you received before joining the study: either 200 mg or 2 mg per kilogram of body weight every 3 weeks, or 400 mg or 4 mg per kilogram of body weight every 6 weeks.

This treatment will continue for as long as it is effective and you do not experience unacceptable side effects.

If assigned to this group, you will receive pembrolizumab combined with chemotherapy medications.

The chemotherapy medications may include one or more of the following, given as a solution for infusion:

Paclitaxel albumin-bound (Abraxane), which is a chemotherapy drug that helps stop cancer cells from dividing.

Cisplatin, a chemotherapy drug that damages the DNA of cancer cells.

Carboplatin, another chemotherapy drug similar to cisplatin that damages cancer cell DNA.

Paclitaxel, a chemotherapy drug that prevents cancer cells from dividing.

Pemetrexed disodium, a chemotherapy drug that interferes with the growth of cancer cells.

The specific chemotherapy medications, dosages, frequency, and duration of administration will be determined by your medical team based on your individual condition and the study protocol.

This combined treatment will continue for as long as it is effective and you do not experience unacceptable side effects.

Throughout the study, you will have regular medical examinations and blood tests to monitor your health and the effectiveness of the treatment.

Imaging scans will be performed at scheduled intervals to assess how your cancer is responding to treatment.

Blood samples may be collected periodically to measure ctDNA levels and other biomarkers (substances in your blood that can provide information about your disease).

Any side effects or symptoms you experience will be recorded and managed by your medical team.

Treatment will continue until your cancer progresses, you experience unacceptable side effects, or you decide to withdraw from the study.

At the end of treatment, final assessments will be performed to evaluate your overall response to the therapy.

After completing treatment, you will enter a follow-up period during which your health will continue to be monitored.

The study team will track your overall survival and long-term outcomes as part of the research objectives.