Lung and heart side effects are common with both radiation and chemo. You're more likely to sustain heart damage if you had radiation to the left side of your chest. There are also radiation side effects that are called late effects because they can show up well after radiation is complete, even decades afterwards.

Fluid in the lungs can develip from radiation, chemo, AIs, and CDK inhibitors. My oncologist checks my lungs every 3 months when I have my appointments to make sure I'm not developing that side effect.

The first time I had chemo was in 2022 and I developed shortness of breath when bending over and when walking 50 to 100 feet. I first noticed it each day when I would bend over to put my dogs food bowl on the floor. The second time I had chemo last year it got worse which was followed by radiation to the right side of my chest, neck, and armpit and it got worse again. I also developed a dry cough during the first round of chemo that has stuck with me ever since. I had been complaining about both since finishing the first round of chemo and the doctor thought it was my heart. I had a few inconclusive echocardiograms between the end of the first chemo and the end of chest radiation that showed leaky valves on one and a potential aneurism on another, but no 2 scans showed the same thing. Then I had a CT scan of my heart and lungs and it turned out my heart was fine. The problem is my right lung developed emphysema from the chemo and radiation. They verified it had started after the first chemo and gotten worse over time by looking back at my past PET scans.

It would definitely be worth the time to see a cardiologist and have some tests done to learn if it's both your heart and lungs that have issues or just the lungs alone having a problem.

Good luck, hopefully they can figure out exactly what's wrong and come up with a solution to stop the fluid build up in your lung ❤️