Sorry not to have got back to you sooner than this, it's a pretty sensitive subject but I remember only too well asking a very similar question when I first joined the forum (under a different name), receiving no answers at all and feeling desperately isolated and alone. So I want to let you know that you are not alone.
Immediately following my rad hyst one of the surgeons told me that more than half of my vagina had been removed. I questioned him and he told me that it was between 50 and 60%. Much more recently I have translated my hospital notes and discovered that the length of vagina sent from the operating theatre to the lab for analysis measured 6 x 2 x ½cm. A year later, several months after chemo, radio and brachy therapies, another examination in a hospital in UK revealed that I had an 'atrophic' vagina. This troubled me so I asked a MacMillan nurse about it and she said that she too had an atrophic vagina, that it was simply one of those things that comes free with menopause. I am not allowed HRT but maybe you are?
At one point I even considered vaginal reconstuctive surgery but my radio oncologist advised against 'in case the cancer returns'. It was a depressing thing to be told when I was already in a pretty dark place :-(
I had already turned 50 when I was diagnosed with cancer, perhaps you are a lot younger than I am. I had been enjoying sex from the age of 15 but after all the treatments it simply wasn't the same. We didn't have sex nearly as often post-treatment as we had before, partly because my hot flushes were just too much to cope with anything much in the way of either physical closeness or exertion. So, as a result, my vagina wasn't kept in tip-top condition and sex went from a little bit disappointing to something of an ordeal and so a little after three years after all my treatments finished we gave it up altogether.
It's very sad. We know some couples in their 60s who have given up on sex for no reason other than menopause and just going off it, and another couple in their 70s who are still banging away. In their case there was a very young hysterectomy so presumably they have had plenty of time to get used to the difference. For me, I've had 38 years of good and happy sex so don't feel that I am missing out too much having hung up my hat. Though I have to say my husband is less resigned to the fact.
I hope you manage to work out things in such a way that you both stay happy.
Be lucky :-)