let me point you first  to:

http://www.bartleby.com/107/212.html
http://www.merck.com/mmhe/sec06/ch095/ch095d.html [not for info on cancer
- just a good diagram of root nerves]
http://www.med.umich.edu/lrc/coursepages/M1/anatomy/html/atlas/abdo_wall72.html
[good xray of area]

now, with that, understand that there are main 'branches' of the nerve
bundles that come out from the main 'cord', and exit the spinal column.
these are the 'root' nerves.

go to the link below, it shows the numbers of each lower vertebrae, and
then click on any of the circled numbers - they will give your the areas
affected:

http://www.lumen.luc.edu/lumen/meded/grossanatomy/learnem/nerves/ls/ls3_map.htm

you might also want to read:

http://www.emedicine.com/sports/topic66.htm

there are multiple reasons why one could have a lesion - 'an abnormal
structural change in the body due to injury or disease' - in this case the
'root' nerve, in your case it would appear [i am not a doctor] that it may
well have started with the disc trauma in the past.

what i know from personal experience is that you must not wait - the
earlier it is definitively diagnosed, and a treatment approach agreed
upon, the better your outcome possibilities. also - be sure to eliminate
diabetes, it can sometimes cause a neuropathy in this area.

http://www.merck.com/mrkshared/mmanual/section14/chapter183/183c.jsp

this next one is fairly heavy technical, but may be worth going over:
http://www.amazon.com/exec/obidos/handle-generic-form/102-8077094-1739301?action
=next-page&target=web-search/redirect.html&ws_page=&ws_position=1&ws_type=google
_regular&url=http://www.neurometrix.com/papers_monos%20pdf/AACN2005PosterSNG.pdf

if your insurance covers it, a ct scan  is often effective in the
evaluation of suspected structural lesions of the lumbosacral plexus.

be well

paul