Would you give full post-operative dose radiation for an undifferentiated high grade pleomorphic sarcoma of the extremity with close surgical margins if the patient had previously received <20Gy preoperatively?

If the patient stopped at 16Gy preoperatively, I doubt they would accept 60-66 Gy postoperatively. Accordingly, I would follow the patient closely with MRI imaging, CT chest, and physical exam. If they developed local relapse without distant mets, I would deliver 45-50 Gy preoperatively (discussing the surgical option of amputation), followed by marginal gross total resection and postoperative brachytherapy or intra-operative electron or HDR-brachy boost.

The following response was drafted together with @Dr. First Last:

We would offer post-operative RT to 50 Gy via shrinking field technique, delivering 34 Gy to a CTV1 similar to that given pre-operatively (as described below, because of the pre-operative RT, the post-operative CTV1 does not need to include scars or drain sites), followed by a boost of another 16 Gy to CTV2, consisting of the tumor bed with 1.5 cm margin, thus bringing the total dose (combining pre-and post-operative RT) to 66 Gy.

While this patient seems to have arrived at it by chance, a strategy of low-dose (15-20 Gy) pre-operative RT, resection, and post-operative RT has actually been used intentionally at Massachusetts General Hospital for several decades in certain sarcoma patients who cannot, for whatever reason, receive a full course of pre-operative RT.  

This strategy was based on the observation decades ago by Brigit van der Werf-Messing in bladder cancer that 3.5 Gy x 3 of pre-operative EBRT prevented tumor cell seeding along interstitial brachytherapy catheter tracts (B van der Werf-Messing Eur J Cancer 1969; B van der Werf-Messing et al., IJROBP 1983). More recently, the same low-dose pre-operative RT regimen was shown in a prospective study to reduce implantation metastases in resectable cholangiocarcioma (Gerhards et al., Eur J Surg Oncol 2000). This is presumably because even low-dose pre-operative RT sufficiently reduces the number of tumor cell clonogens to measurably decrease the likelihood of iatrogenic tumor cell seeding during surgery. 

This approach was initially applied to sarcoma by Herman Suit and colleagues, where it has several potential benefits. Compared to full-course pre-operative RT, it limits the risk of acute wound healing complications because the pre-operative RT dose is so low. Compared to post-operative only RT, it minimizes the risk of surgical site seeding such that coverage of the entire surgical site, scar, drains, etc. during the post-operative course is typically not necessary. Thus, post-operative RT volumes in this approach closely resemble typical PRE-operative RT volumes, and these more limited fields may also help to reduce the risk of late RT complications. This approach is particularly useful in cases where the patient cannot receive a full course of pre-operative RT (for example, due to concerns for acute wound healing complications or urgency of surgery), or where post-operative RT alone could not cover all at-risk tissues (for example, if surgical violation of the pleural or peritoneal cavities is anticipated). While this does represent a ”split-course” approach to RT, the radiobiological disadvantages of split course RT seen in carcinomas are unlikely to be as relevant to sarcomas, as the relatively slow doubling time of sarcomas limits tumor cell repopulation between the two RT courses.  

The MGH experience with this approach has been published for both bone sarcomas (Wagner et al., IJROBP 2009) and soft tissue sarcomas (Devisetty et al., IJROBP 2011), and is currently being updated for the latter (link). Oncologic outcomes of this approach appear comparable to standard post-operative only RT.

David Konieczkowski MD PhD
(Chief resident, Harvard Radiation Oncology Program)

Thomas DeLaney MD
(Andres Soriano Professor of Radiation Oncology, Massachusetts General Hospital)

I would simulate the patient and then try to fuse preop scan. Much of what received 16 Gy is excised, so I would look at the dose to the bone. I would then plan to give 60-66 Gy and look at the composite dose to bone while sparing the strip to avoid lymphedema. I would counsel the patient on a potential increased risk of toxicity, but would try to, at a minimum, give 60 Gy.