Table 2 Summary of exploratory studies that tested pharmacodynamic value of ctDNA

Colorectal

Diehl et al. (2008)

18 (16 stage IV, 1 stage III, 1 stage II)

Surgery and/or chemotherapy

APC, KRAS, p53

ctDNA reflects the tumour burden

ctDNA is more reliable and sensitive indicator of disease than CEA

Pancreatic

Olsen et al. (2009)

11 (locally advanced)

Chemo-radiotherapy and gefitinib

KRAS

Five patients had ctDNA in pretreatment plasma

Of those five patients, ctDNA became undetectable in 3 patients post-treatment and they had overall survival of 8, 11, and 21 months

Breast

Chen et al. (2009)

6 (non-metastatic)

Neo-adjuvant chemotherapy

p53

ctDNA were undetectable after treatment in four women consistent with clinical remission

Cutaneous melanoma

Shinozaki et al. (2007)

48 (stage IV)

Bio-chemotherapy

BRAF

Twenty-four patients responded to treatment

Ten responders had ctDNA in pretreatment serum and nine of those had undetectable ctDNA in serum within 4 weeks of the last cycle of treatment

BRAF mutation in serum is associated with significantly worse overall survival