On february, my chest x-ray showed an increase in interstitial marks. in march i was diagnosed with stage4nsc lung cancer. was the increased interstitial marks a sign?

Yes or no: As cancers spread in the lungs, they can cause what we call lymphangitic spread of disease. Those lymph vessels are along the blood vessels and yes they can look like increased interstitial markings. To make a decision from that alone would be difficult unless a mass is seen or a diagnosis established beforehand. Even radiation pneumonitis looks the same. Decisions are made from previous diagnosis.