I had my Prostate surgically removed in April 2015 when I was 70, luckily I've had no problems since and still lead a full and active life.
The worst time for me was having to wear a catheter, a tube, and a urine bag for 10 days. I was uncomfortable because of tube weight at the penis end and the way it affected my personal comfort there. In the end, I did a 'Heath Robinson' adaptation to my underwear to help my predicament. I cut a small hole into the fabric on the side 'that I dressed' to ensure that my penis and tube before it came out of my underwear, was more or less in the horizontal position before the tube curved down vertically to the urine bag. This solved my problem until the catheter was permanently removed and I returned to normality. At the time my underwear was standard M & S boxer type briefs.
I do a lot of long-distance hiking and camping (between 10-15 miles a day) in all terrains and last year I bought some boxer type stretchy underwear from Decathlon the sports shop chain. I now have a number of pairs, they cost £3.99 each and I wish I'd known about them in 2015. For such a cheap item they fit so well, they grip comfortably in all of the right places, hips, bum, waist, and abdomen but do not grip where they shouldn't! I'm a 32" waist and I first bought a 'M' and an 'L' to find out which was best for me and I now buy the 'L' sizing, they grip me well but not so tightly as the 'M' ones.
'On the trail' they are so easy to wash, dry very quickly and are very light in weight. If I'd worn them in 2015 I'm sure I would have been happier with my catheter than I was with my M & S underwear.