Simultaneously simple.

Top Line: Can you safely treat pelvic nodes simultaneous with moderately-hypofractionated prostate radiation?

The Study: We sure hope so since everyone does it. But it turns out this very practical question has surprisingly limited data. On the one hand, it’s simply a combination of a conventionally-fractionated dose to the nodes with a moderately-hypofractionated dose to the prostate using a simultaneous integrated boost technique. But, on the other hand, nodes weren’t treated in the majority of the moderate-hypofractionation trials, meaning organs at risk may be more at risk than we thought. Here are long-term results from a single-institution (McGill University in Montreal) phase 1/2 trial of patients with clinically node-negative high-risk prostate cancer receiving 60 Gy in 20 fractions to the prostate plus up to 1 cm of the proximal seminal vesicle and 44 Gy in the same 20 fractions to the pelvic (read: distal common iliac and bilateral internal and external iliac) nodes. Rectal dose constraints were: V60<15%, V56<25%, V52<35%, and V48<50%. Bladder constraints were: V60<25%, V56<35%, and V52<50%. Compare these to the much stricter 20-fraction dose constraints derived from CHHiP. The rates of acute grade 2-3 GI and GU toxicity were 17% and 15%, respectively, while cumulative late grade 2-3 GI and GU toxicity were 7% and 10%.

TBL: Simultaneous pelvic nodal irradiation with 20-fraction prostate hypofractionation appears (cough, cough, see below) to be a safe option to deliver comprehensive radiation. | Faria, Pract Radiat Oncol 2020

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