No trial is perfect and in hindsight, the choice of TTB as a primary metric appears to weigh heavily on the assessment of outcome in this trial.MIRAGE syndrome is a condition characterized by Myelodysplasia, Infection, Restriction of growth, Adrenal hypoplasia, Genital problems, and Enteropathy (intestinal problems). TTB is a metric that takes any well educated reader probably 30 minutes (minimum) time to have any chance to really interpret for themselves across multiple references. So very easy statements of “no difference” easily wash away a benefit seen in a new rather complex toxicity metric. On first glance QoL, PFS, OS - all the same. But looking back and looking much deeper, I don’t think that is the case, but in today’s world 95% will never look again. I was in the room during the data presentation and it didn’t feel like “a big win”. ![]() Unfortunately some of outcome differences in this trial, from my perspective, got buried in the presentation and publication. One cannot and should not compare the post-operative complication rate difference in this trial to Gr2 prostate cancer toxicity. )Īnd the toxicity differences are in FAR more important items than the MIRAGE trial. It does include a weighting metric you must agree with, but even if you don’t think the weighting is perfect, complications are still worlds apart. (Read that again - it is a massive difference. Restating the results, in patients undergoing surgery, the risks of anastomotic leaks, ARDS, pulmonary embolism, reintubation, and stroke were 7.6 times more severe if treated with IMRT instead of PBT. The deeper I look, the more this trial does demonstrate a very significant win for proton therapy. So unlike the MIRAGE trial, the technology advantage is not utilized to increase dose or reduce margins, but rather simply to attempt to demonstrate a reduction in toxicity within a well established standard of care therapy where toxicity is relatively high. Perhaps, if the toxicities directly resulted in death, there might be some hint of OS difference but certainly not by design and not powered for that endpoint and PFS should be unchanged. In the trial both modalities deliver the same dose so the likely expectation was to see equivalent PFS with less TTB. And although elegant and seemingly well designed, I believe it ends up being a weakness and argument against the trial outcome. The goal is reasonable, measure cumulative toxicity over time between two treatments, but it is not a common well-known metric. TTB is a created cumulative toxicity scale created at MD Anderson. The two primary metrics were total toxicity burden (TTB) and progression free survival (PFS). ![]() Can this improve outcomes by reducing toxicity in patients with esophageal cancer treated with concurrent chemotherapy radiation (about half of whom went on to surgery)? (ref 3) The basic question: Protons have a dosimetric advantage over IMRT. So lets now look at the Esophageal RCT and compare. I moved my practice for access to proton therapy for head and neck cancer trying to push for less toxicity - so by default, I’m a believer that we can do better. I think it was a positive trial and important for radiation oncology to show an outcome difference via technology. That said, I’d be more inclined to travel for the MD’s expertise than the machine.Īt the end of the day, it appears to be a small incremental step forward in a site with minimal treatment related toxicity. I think the treatment team involved is top tier and delivering top-tier world leading, super high quality treatment. If I lived in the backyard of an MRI linac, I’d likely choose that program over a typical linac platform. I think this shows the technology probably helps a little. Decreasing margins does have some, at a minimum, potential for increased recurrence and it should be, at least, a secondary outcome.īut my personal take? I like pushing aggressively for lower toxicity. I’ve argued against this since the early robotic surgery trials looking only at toxicity and I dislike it here. Further the bowel dosimetry wasn’t better which, I think, should at least bring up questions as to the reproducibility of the bowel toxicity findings.įinally, I personally really dislike not having any tumor outcome in any trial that potentially can be held up as “important”. If we believe that bladder treatment of <2cc at 39Gy is the difference, it is surprising that rectal spacing gel and pelvic treatment differences can’t be measured. ![]() I’m personally less convinced of the bowel data presented (but in my clinical experience with SBRT it wouldn’t shock me that smaller treatment volume is slightly better). From the paper data, I think it shows a little less Gr2 toxicity on for bladder. The trial shows a little less toxicity with margin reductions.
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