DNA derived from tumour cells can be detected in plasma. Persistence of genetic defects in circulating DNA can predict recurrence some types of cancer but has not been demonstrated in oral carcinoma. Objectives: To establish whether genetic alterations that are observed in tumour and pre-operative circulating DNA are maintained in circulating DNA after surgery and if their analysis is of use in predicting outcome. Methods: DNA from tumour tissue, white blood cells, and pre- and post-operative plasma was subjected to PCR analysis of 22 microsatellite markers. Densitometry was used to assess allelic imbalance. Results: The table summarises the data. Follow-up plasma was obtained at 11-22 months post-surgery. 2/6 patients had no detectable circulating DNA at follow-up and have no sign of recurrence. Follow-up circulating DNA retained previously observed allelic imbalance in two patients who developed recurrence. The remaining two patients have not recurred but do demonstrate persistent AI. These patients may be harbouring sub-clinical disease. Conclusion: These data show the potential for the longitudinal analysis of circulating DNA to aid the early detection of recurrence, at least in a proportion of patients. Larger prospective studies to evaluate this hypothesis are ongoing. Funded by British Society for Oral and Maxillofacial Surgery
|
SITE |
TNM |
Invasion (mm) |
Tumour AI (markers with ai informative markers) |
Pre-Op Plasma AI |
Follow-Up Plasma AI |
Outcome+
|
|
Alveolus mand. |
T1N0M0 |
5mm |
4/14 |
3/4 |
NR* |
NSR (93m) |
|
Tongue post1/3 |
T2N0M0 |
4mm |
1/9 |
0/1 |
NR* |
NSR (37m) |
|
Floor of mouth |
T2N2bM0 |
12mm |
6/15 |
2/6 |
2/6 |
NSR (31m) |
|
Tongue post 1/3 |
T3N2aM0 |
18mm |
5/12 |
NR* |
2/5 |
NSR (24m) |
|
Retromolar fossa |
T4N2bM0 |
15mm |
8/18 |
6/8 |
5/8 |
Died LR (23m) |
|
Alveolus mand. |
T4N2cM0 |
22mm |
8/16 |
3/8 |
1/8 |
Died LR (17m) |
*: NR = No Result +: NSR = no sign of recurrence; LR = local recurrence