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NSCLC — SCE Medical Oncology MCQ

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HardLung CancerNSCLCSCE Medical Oncology

For a medically inoperable peripheral stage I NSCLC more than 2 cm from mediastinal critical structures, the RCR lists 54 Gy in 3, 55 Gy in 5 and 60 Gy in 8 fractions as SABR options. Using BED10 = nd[1 + d/(alpha/beta)] with alpha/beta = 10 Gy, which listed schedule has the greatest tumour BED10?

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Correct answer: D — 54 Gy in 3 fractions, giving a BED10 of 151.2 Gy

For 54 Gy in 3 fractions, d is 18 Gy and BED10 is 54 x (1 + 18/10) = 151.2 Gy, the largest value. For 55 Gy in 5, BED10 is 55 x 2.1 = 115.5 Gy. For 60 Gy in 8, BED10 is 60 x 1.75 = 105.0 Gy. For 50 Gy in 5, BED10 is 50 x 2 = 100.0 Gy. For 60 Gy in 15, BED10 is 60 x 1.4 = 84.0 Gy. The calculation does not mean the highest-BED schedule is suitable near central organs at risk; the stem specifies favourable peripheral anatomy.

Reference: Royal College of Radiologists dose-fractionation recommendations, fourth edition (Published January 2024): https://www.rcr.ac.uk/media/0d4mrqi5/radiotherapy-dose-fractionation-fourth-edition.pdf