TABLE 1.

Definitions of initial treatment

Initial treatment category	Definitions
A. Surgery	Surgery for SCLC at any time point (regardless of any other treatment received)
B. Radiotherapy alone	Radiotherapy + no SACT nor surgery within 90 days (3 months) after radiotherapy
C. SACT + radiotherapy	Sum of C1, C2, C3 and C4
C1. Radiotherapy followed by SACT	Radiotherapy + identification of SACT within 90 days (3 months) after 1st radiotherapy regimen + no surgery
C2. SACT followed by radiotherapy	SACT + identification of radiotherapy within 42 days (6 weeks) after start of last SACT cycle + no surgery
C3. Induction chemoradiotherapy	SACT + radiotherapy within less than 54 days (9 weeks/~3 cycles) of SACT initiation + no surgery
C4. Non‐induction chemoradiotherapy	SACT + radiotherapy starting at least 54 days (9 weeks/~3 cycles) after SACT initiation but before the end of the start of the last SACT cycle + no surgery
D. SACT alone	SACT + no radiotherapy nor surgery within 150 days (5 months) of 1st SACT regimen start
E. Not treated	No SACT, surgery or radiotherapy identified over entire follow‐up period

Note: Initial treatment was defined as the first treatment received within 3 months of diagnosis, associated with any other treatment received within a time period following first treatment as described above.

Abbreviations: SACT, systemic anticancer therapy; SCLC, small cell lung cancer.