How do you interpret NCCN chemoRT dose recommendations for SCLC which start higher than NSCLC?

Dose recommendations for NSCLC are to use at least 60 Gy, but for SCLC recommendations are for higher doses starting at 66 Gy. Classically, SCLC is more radiosensitive and thus would be the histology with the slightly lower dose range. Are we constrained by the trials that have been performed?

1 Answer

Mednet MemberInvited Expert

Radiation Oncology · Memorial Sloan Kettering Cancer Center

Answered on

I understand the questioner's logic that because SCLC is traditionally considered more radiosenstive than NSCLC, it may seem discordant that guidelines recommend 66Gy for SCLC but 60Gy for NSCLC. However, I would still abide by these guidelines because as the questioner suggests, these doses are based in robust randomized trial data.

To be clear, the recommended dose for SCLC is actually 45Gy BID in twice-daily fractionation, not 66Gy in daily fractionation--so in that sense, there is concordance between the recommended doses and the purported radio-sensitivity of SCLC vs. NSCLC.

However, the 60Gy recommendation for NSCLC comes from the RTOG 0617 trial which showed no advantage to 74Gy over 60Gy (hence 60Gy is the standard). For SCLC, 66Gy comes from the CONVERT trial which compared 66Gy daily vs. 45Gy BID. This failed to show superiority of 66Gy daily over 45Gy BID so 45Gy BID remains the standard, but as there was also no significant difference in survival between the two arms either, this also supports giving 66Gy in situations where twice-daily RT is not being used for whatever reason.

Though one might speculate that 60Gy or even lower might be equally efficacious as 66Gy for SCLC, this has not been tested in a prospective fashion and therefore, 66Gy is recommended for once-daily RT in SCLC.