Proximal colon cancer in patients aged 51-60 years of age should be tested for microsatellites instability. A comment on the Revised Bethesda Guidelines.
OBJECTIVE
The Bethesda guidelines suggest to perform microsatellite instability (MSI) test in early onset rectal cancer and not in patients>50 years with proximal colon cancer. The aim of the study was to evaluate whether the risk of high MSI (MSI-H) is greater in proximal colon cancer of patients 51-60 years old than in early-onset rectal cancer.


METHODS
Consecutive colorectal cancer (CRC) patients were evaluated. Tumor location, cancer family history, MSI status and histology were recorded. Mutations in MLH1/MSH2 were investigated in MSI-H tumors. Patients were subdivided into groups: group A, proximal colon cancer patients 51-60 years old and groups B, C and D, patients<or=50 years old, with rectal cancer, proximal and distal colon cancer, respectively.


RESULTS
Out of 409 CRC patients evaluated, 48 (12%) showed tumors with MSI-H. No MSI-H tumors were found in distal and rectal tumors of patients at sixth decade of life. Group A included 27 patients, eight (29.7%) MSI-H cancers, four missense mutations in MLH1/MSH2; groups B, C and D included 26, 11 and 11 patients with two (7.7%), two (18%) and two (18%) MSI-H cancers, respectively. One missense mutation on MSH2 in group B, one pathogenetic mutation on MSH1 in group C and one pathogenetic mutation on MSH2 in group D were found. Tumors of group A showed an increased probability to have MSI-H if compared to those of group B (OD=4.907, p=0.043).


CONCLUSIONS
The Bethesda criteria should be broadened to include patients 51-60 years old with proximal colon cancer.
Urso
E
E
Clinica Chirurgica II, University of Padova, via Giustiniani 2, Padua, Italy.
Pucciarelli
S
S
Agostini
M
M
Maretto
I
I
Mescoli
C
C
Bertorelle
R
R
Viel
A
A
Rugge
M
M
Nitti
D
D
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D000230:Adenocarcinoma / Q000235:genetics; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003110:Colonic Neoplasms / Q000235:genetics*; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D005820:Genetic Testing; D006801:Humans; D008297:Male; D053842:Microsatellite Instability; D008875:Middle Aged; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein / Q000235:genetics; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics; D017410:Practice Guidelines as Topic; D012004:Rectal Neoplasms / Q000235:genetics*
D048868:Adaptor Proteins, Signal Transducing; D004273:DNA, Neoplasm; C501486:MLH1 protein, human; D009687:Nuclear Proteins; C497172:MSH2 protein, human; D000070957:MutL Protein Homolog 1; D051718:MutS Homolog 2 Protein