Hi Terry,
Unfortunately for people like us who want to do the very best for our bodies that we can, nutrition and supplementation and their effects on treatment haven't been given the strongest emphasis in medical schools. Consequently there are literally hundreds and hundreds of drs out there who don't really know how to answer patients' questions about what supplements they should or shouldn't take with certain drugs, disease processes, etc. (Both my family practice doc and my oncologist will admit as much to me - but many other docs won't admit that they don't know a lot about nutrition and that they don't see any pressing need to learn.) I think the situation has gotten somewhat better than when I went to nursing school in the early 80's, but quite possibly it hasn't gotten a whole lot better.
When the big gun cancer drugs were developed, starting in the 60's and 70's, there wasn't a whole lot of attention paid to the interaction of vitamins, minerals, and foods - unless there was something that just absolutely hugely stuck out that caused a problem, many drs were taught that a multiple vitamin was all that was needed and in general it wouldn't cause any problems. There was a big push at that time by certain pharmaceutical companies to use products like Centrum Silver - and that is what has stuck as far as most MD's recommendations go, even several decades later.
As time has gone on, it's been found out that there are some drugs that really can get interference from this or that natural compound - and those things have been incorporated into the pharmacology and drug reference books and printed on the packaging information of individual drugs, but that doesn't mean that all the drs are caught up on everything that's been learned.
I took some time and looked at online references to product information for Doxil from the manufacturer - these are the food and over-the-counter drugs and supplements I found that are contraindicated:
turmeric - avoid any kind of turmeric spice in food as it decreases the effectiveness of Doxil. This would also indicate avoiding curcumin supplements - curcumin = turmeric.
aspirin - avoid aspirin unless ok'd by your dr
progesterone - avoid prescription progesterone products. I would avoid any kind of over-the-counter progesterone, just to be safe. You might also look on the web for foods that are especially high in phytoprogesterone, and avoid those also.
http://www.rxlist.com/doxil-drug.htm
http://www.webmd.com/drugs/drug-12120-Doxil.aspx?drugid=1212
The real threat with Doxil is toxicity to the heart. Even though the lyposomal doxorubicin (Doxil) is supposed to be gentler on the system than the original doxorubicin hydrochloride (Adriamycin - or otherwise known as the Red Devil - with good reason), it still can be exceedingly hard on the heart (and the liver, but more so the heart.)
I've found that naturopathic/holistic practitioners - including naturopathic drs, are among the best in terms of recognizing the importance of nutrition in treatment, and are among the most knowledgable as to which foods/supplements/ herbs are safe to take with specific medications, and which should be avoided. I did find one site by a naturopathic dr that talks specifically about the effects of Doxil and those things that might best protect against cardiac toxicity:
Coenzyme Q10 - may reduce heart toxicity
Vitamin E may reduce heart toxicity (controversial).
Selenium, Glutathione and Vitamin C
Antioxidants may reduce heart toxicity and increase survival time.
http://www.naturdoctor.com/Chapters/Drugs/Doxorubicin.html
So, if you want to take your vitamin c, and whatever - and whoever it is actually prescribing your chemo has no objection, then I say go for it. (You mentioned two dr's in your post - I would pay most attention to the dr who is actually doing the prescribing, as they are the one who is sposed to be keeping track of everything that is going on with you in terms of cancer treatment.)
I hope this helps, and I wish you the best with your treatment.
Sincerely,
Tre