Lymph nodes - possible involvement decision even if nothing on CT or MRI

As some of you are aware, I’m going for Brachytherapy Boost (a form of HT/RT : see my bio for details). I didn’t realise until recently that I had another decision to make - whether to have one of these two variants:

radiotherapy to just the prostate and immediate area (taking in a safe margin, nerve bundles and also the immediate lymph nodes).

radiotherapy to the wider pelvis area, taking in lymph nodes all the way up to L5.  This will, of course, increase my risk of gastric & urinary side effects (any side effects will, hopefully, reduce over time). 

I have chosen the second option, after reviewing the recent trials results (ASCENDE-RT, and PIVOTALboost) and also reading a very interesting thread on the PCUK site.   Here’s a precis of my research this morning, which some of you may find of value:

There are two types of lymph node involvement:  

1.  The lymph nodes immediately next to the prostate: as lymphatic fluid flows through the prostate, it picks up tiny cancer cells and carries them into the nearest lymph node where they are filtered out and stopped going off down the lymph highway. This is described as N0 or N1 (if cancer invades the lymph node) on the diagnosis letter.  

2.  The lymph nodes away from the immediate pelvic area:  if cancer cells are found in these, they have indeed set off down the highway.  This is described as N1 and even M1 (distant mets) on the diagnosis letter.  

How the system works: 

Lymph fluid leaks through cell walls and blood vessels into the spaces between them, and is mopped up by the lymphatic system, which collects this and adds in loads of antibodies and T cells to kill any bacteria and viruses present. Areas of injury or infection also get swamped with lymph to try and clean them up and disinfect them. 

The lymph nodes filter out and kill any cells in lymph fluid, including cancer cells. While they're successfully doing this, you're OK. Eventually however, either some cancer cells leak through, or they're filtered out but not killed, and grow in the lymph node. Then you will need an alternative treatment pathway. 

Lymph fluid passes through many lymph nodes as it passes back through your body heading towards your collar bone area, where after multiple filtering, it drains back in to your blood stream. If cancer is found only in the lymph nodes immediately draining your prostate of lymph, that's likely to be more curable than if it's found further along the pathway, which is why staging identifies it as N1 when near the prostate, rather than distant lymph nodes which is identified as M1.  In the latter case, the cancer cells have already leaked through many lymph nodes and further micro-mets are likely to have been established even if not yet found. 

HT/RT Route. 

If you are diagnosed N0:  With radiotherapy of high risk cases, prophylactic treatment of pelvic lymph nodes is sometimes undertaken, even if it wasn't found in them, just in case micro-mets had already set up in there but not shown on scans. This can cure cancer in the lymph nodes with a better prospect of leaving them still working afterwards, as normal lymph cells can recover but cancer cells can’t.  This may also apply if you’re N1.   If you are diagnosed M1: Cancer has been found in lymph nodes away from the immediate pelvic area. So RT to the pelvic area would be pointless.  

Prostatectomy Route. 

With surgery, pelvic lymph node dissection (PLND) is sometimes included, hoping to go as far as taking all nodes with any mets in them. But you can only be reasonably sure of if you've gone as far as the first node in the chain with no mets. The trouble here is that may involve taking nodes which drain other areas such as groin and/or legs, leaving those areas with no lymph no drainage anymore.  In this case, lymphoedema - where water can't drain anymore – is likely, debilitating and not resolvable.