Supplementary Material for: Impact of tumor shrinkage pattern with biweekly triplet gemcitabine+cisplatin+S-1 regimen for biliary tract cancers: Implications for neoadjuvant therapy from the data of KHBO1401 (KHBO1401-1A study)

Background:
The multicenter randomized phase III KHBO1401 study (gemcitabine+cisplatin+S-1 [GCS] versus GC in biliary tract cancers [BTC]) demonstrated that GCS not only prolonged patient survival but also achieved a high response rate and that it should be good for neoadjuvant therapy. Therefore, to explore the possibilities of neoadjuvant therapy, we investigated the tumor shrinkage pattern.
Methods:
Among the total of 246 patients enrolled in the KHBO1401, the tumor shrinkage pattern and survival were investigated in patients with measurable BTC (n=183, 74%; GCS, n=91; GC, n=92).
Results:
The tumor shrinkage pattern could be divided to 4 categories based on the response at 100 days after enrollment: category A (<-30% in size), B (-30% to 0%), C (0% to +20%), and D (>+20%). The GCS arm included more category A and B cases (61 [67%] vs. 33 [36%], P<0.0001). Each category predicted best response and overall survival (P<0.0001). Category A showed sustained tumor response compared with category B; in GCS, the time to maximum tumor response was 165 ± 76 days in category A and 139 ± 78 in category B. Categories C and D did not achieve tumor shrinkage. The maximum tumor shrinkage size in category A was -53% in the GCS arm and -65% in the GC arm (P=0.0892). Twenty percent of patients in the GCS showed tumor regrowth 154 ± 143 days later.
Conclusion:
GCS provided faster and greater tumor shrinkage with better survival in comparison to GC, although 20% of patients showed re-growth after 6 cycles.