Persistent pain post stenting - looking for post stenting survivor experiences

Hello:
I shall start with a some background information of the patient (my Dad), before posing my question to this forum. My Dad is 67-1/2 years old and was diagnosed with esophageal cancer (adenocarcinoma) this march. He has stage IV cancer with a primary tumor at the esophagus - stomach junction and some secondary nodes in both lobes of the liver. Due to a high creatinine level, he was unable to undergo a more agressive chemotherapy treatment. Also, a recent angioplasty due to minor blockages in his coronaries (though not a major arterial block), added to the Doctor's hesitation in putting him on a aggressive treatment routine. We were told that since the cancer had spread to both lobes of the liver, there were'nt many treatment options and any treatment from here on would mostly be palliative. He was put on a chemo regime that is processed mainly through the liver thus avoiding taxing his kidneys or increasing his creatinine levels. He is on a 1/3rd chemotherapy dosage per week thus breaking up each round of chemo into three weeks which gives enough time for his body to cope with the treatment effects. Thankfully he has not had many persistent chemo related side effects. He has some of these side-effects (irregular bowel movement, tingling, hiccups) briefly for a day or two after the chemo but nothing persistent.

Coming to my question. My Dad had a CT scan after 3 chemo rounds. Although there has been a significant improvement at the secondary sites (liver), there has not be appreciable improvement at the primary location. Thus the Doctor conducted a stenting procedure to avoid any swallowing complications in the future (he has been able to have semi-solids, even before stenting). But my father had severe pain post the stenting procedure for about two weeks. After three weeks from the procedure he resumed his chemotherapy. Although the pain intensity is much lesser now, Dad is still in discomfort. I've read about pain from stenting lasting for 10-17 days but this has persisted past 4 weeks now. He is not having problems swallowing food, his blood-work is improving each week and creatinine levels are dropping steadily (2.4 at diagnosis to 1.7 presently). X-rays indicate that the stent is in place.

I was wondering if anyone knows of a similar case where the post - stenting pain has persisted so long. The doctor's don't seem to be very clear/convincing as to why he's still in pain. Though I must add that due to his renal and cardiac condition he was given basic pain killers after the procedure unlike the morphine dosages given to most patients undergoing this procedure. We are eagerly looking for some guidance/direction on this issue. Dad had been pretty courageous and positive up until the stenting but this constant discomfort is starting to affect his mood and general demeanor. I think the suspense of not knowing what is going on is bothering him and preventing him from dealing with the issue. I apologize for going a bit overboard with the description of his condition, but if you have managed to read this far and know something that might shed more light, then please do reply. Any help in this regard is greatly appreciated.

Regards,
Mainak