I have one that had a lash egg. Many publish that the time from lash egg to death is anywhere between a few days to a few months, but mine is at 15-months. A lash egg is evidence of a bacterial or viral infection, however, more than 90% of the time it is bacterial. My vet has her on 250mg/5ml, 1mL per day for 10-days (liquid, I do it by syringe), but when she went off and lash egg material reappeared, we now do pulse therapy. The only "real" chance of allowing the antibiotic to get rid of the infection is an implant, luprolide acetate injections or a Salpingohysterectomy (too much anesthesia risk).
I now have one with reproductive CA. My vet cannot do luprolide injections or suprelorin implants because it is not approved in the United States (it is in other countries). However, I found a source outside the US and am doing luprolide injections myself for both. The implant or luprolide allows the ceasing of egg laying to give their bodies a fighting chance to overcome the infection. In the case of CA, it is just buying more time.
In summary, our chickens have been bred to lay 12x more eggs than they do in the wild. The constant irritation causes constant inflammation. The perfect environment for infection and cancer.