For your question about side effects, it would depend greatly on where the tumor was exactly. Radiation is a focused, local treatment, so its side effects are limited to the area treated. Often, a chondrosarcoma on a distal appendage, this greatly limits the short term side effects other than skin irritation and fatigue. Muscle can take very high doses of radiation without much in the way of side effects. Chondrosarcoma by definition is near a joint. This can mean that the joint can become stiffer over time - off set to some degree by exercise and moving the joint. The biggest long term side effect that we worry about is a tumor caused by the radiation itself. This is very uncommon and is dependent upon the age of the patient (the younger the patient, the longer they have to develop a second cancer). You should talk to your RadOnc about what that risk might be for you.
I hope this helps.
Long answer: While there is no "safe" dose of radiation to a developing fetus, dose to a developing fetus is likely very, very low if done with modern mammography equipment. Most mammogram units have a plate that is installed perpendicular to the machine just below the imaging plate. This ensures that a woman’s stomach does not get in the way of the image (if she is overweight). This plate is also shielded to avoid excess radiation dose to a woman’s stomach/bowels. In your wife’s case, this likely provided shielding for the developing fetus in her uterus. Although the risk to the fetus was diminishingly low, I would still talk with her OB-GYN about your concerns.
Long answer: The median survival of someone over 70 with Stage 4 lung cancer is about 2-4 months. The fact that you say it is making him weak is a bad sign and likely puts him on the lower end of that spectrum. Chemotherapy comes in many flavors, some more toxic than others and some more effective than others. I would discuss your father’s goals of his care to get a clearer understanding of he wants “everything done that can be done” or would rather just focus on being comfortable.
Without knowing any of the above, the average survival of a Stage 4 lung cancer patient is about 2-8 months, but this is a great question to ask his medical oncologist who could give a much better estimate.
Longer answer: We know that chronic irritation of the lung can lead to a type of lung cancer called Squamous Cell, but by chronic, I mean years and years of nonstop irritation. And even then it would have to be in the same location as the irritation. IF the cancer was in the same spot as the pneumonia, the likely answer is that the cancer was there at the time, it just could not be seen because of the pneumonia.