You can always seek a 2nd opinion, but will be asked, why, being you are already being treated elsewhere, and may even not been seen. Major CCC pick you, you do not pick them. I was denied as consultation at MSKCC for my last recurrence, even after I sent them 400 pages of documents, 10 cd's, and said sorry. My current RO, who was also in consideration, then said, I know you have been searching around lol, but you will not get a better offer elsewhere than what I'm offering you. No doctor is obligated to see or treat you.

Sometimes you have to trust your MO, who is overall in charge of your treatment planning, and physicist. I would not insult him by requesting to see the physicist or treatment plan, which is very complex mathematics, and they probably put them into a sophisticated program. I sought out the best RO, researched his background, read his abstracts, and many books. I'm somewhat familiar with the treatment planning, equations by name only, with QL, GTV, BED, EQD, etc. but is beyond my scope to figure out.

Also, you already started the train rolling by having 2 rounds if induction chemo.
Your time is more limited, and have to complete the whole "treatment package" in a certain time, for optimal results. Getting a 2nd opinion, going elsewhere, will take time, and some may require thier own testing, scanning, and planning, which takes up more time, but it is better to delay radiation, than to disrupt it, but should be for good reasons.

You can always ask any question politely, by not being insultive and not effecting future relationship with your doctor, and each can be different in thier response. I do have copies of my records, and treatment planning report with the cumulative dose volume histogram, ratio of total structure volume, target volume, fractionization, fields, color CT images, etc after I started or rather completed treatment, for my records.

I hope this helps.