What would your RT volumes be for a high grade sarcoma of a joint (such as the knee) after a gross total resection?

Receiving patients in the post-operative setting can be saddening knowing that a pre-operative regimen of radiation would be a lesser dose and volume resulting in a lesser chance of late-term toxicity as shown in the long-term follow-up of the NCIC study comparing pre-op versus post-op radiotherapy. Having said that, we still do occasionally see post-operative patients.

In the pre-operative setting you have the concerns of a large operative bed inclusive of drains and a scar that is sometimes longer than the original volume. I still like the Haas RLM, IJROBP 2012: 84(3): 572-580 reference as a guide for contouring and treating in the post-operative setting. The paper gives detailed instructions, but the initial CTV should be constructed by expanding the surgical volume by 1.5cm radially and 4cm longitudinally (I would cut back at bones, fascia and joints not compromised at the time of surgery). In the setting of pre-op RT, RTOG 0630 (Phase II trial) gives tighter volume options for CTV and PTV expansions when using IGRT. Although not proven in a phase III trial the results have shown good toxicity with low local recurrence and I have shifted my contours to reflect the study.

In regards to the joint and terms of fibrosis, both RTOG 0630 & the current COG-ARST 1321 recommend a V50 of <50% to the joint. However, I have found it interesting that there is no good guide, I am aware of, for contouring the "joint". Therefore, given the potential volume and length a "joint" could be contoured as I am sure there would be a large variability in the numbers a plan could generate radiation oncologist to radiation oncologist. Having said that, have there been times that I have given a greater dose to a joint than that? Yes. If I can selectively avoid the joint or minimize the dose to a joint I will. However, if it is at risk of local recurrence, than I will treat knowing that there is a higher chance of fibrosis to improve the local control and prevent future amputation.

In the 2 patients I have treated to the joint with higher doses I did not have noticeable fibrosis. They tolerated the treatment well and 1 of the patients developed lung mets at 1 year out never suffering local toxicities before he became hospice bound. In fact, the data supporting the dose constraints for joint toxicity are not clearly supported to me and given the other factors such as: size of original tumor, extremity edema, surgery, type of closure, chemo, age of patient and activity, of patient I am sure fibrosis of the joints could be a multifaceted problem. In patients at high risk of fibrosis I was able to have them ambulatory at the time of RT, prescribed physical therapy and treated them with Vitamen E and trental to help prevent fibrosis.