Effect of radiation therapy on the potential doubling time of tumours in colorectal cancers.
OBJECTIVE
The aim of the present study was to investigate the effects of standard fractionated radiation therapy on the kinetic parameters of colorectal adenocarcinomas.


METHODS
The study of tumour kinetics involved in vivo injection of bromodeoxyuridine. Endoscopic biopsies were obtained from the tumour and analysed with flow cytometry. This procedure provides a rapid calculation of qualitative parameters such as ploidy and quantitative parameters such as the in vivo S-phase fraction labelling index which indicates the percentage of cells that have entered into the cycle, the duration of S-phase (Ts) and the potential tumour doubling time (Tpot).


RESULTS
Thirty-eight colorectal carcinomas were studied without prior chemotherapy or radiation therapy (group 1) and ten rectal carcinomas were studied following radiation therapy (group 2). In diploid tumours, the labelling index was significantly lower in the post-radiotherapy group than in the pre-radiotherapy group (2.7 +/- 1.1% versus 6.4 +/- 4.2%, respectively; P= 0.01), and the Tpot was significantly longer after radiotherapy (group 2) (22.0 +/- 7.0 days versus 8.6 +/- 6.0 days, P = 0.002). Standard fractionated radiation therapy also appears to result in a longer Tpot in diploid adenocarcinomas of the colon and rectum. This effect was not observed in aneuploid tumours.


CONCLUSIONS
The effectiveness of hyperfractionated schedules of radiation therapy for aneuploid rectal tumours with short Tpot warrants further investigation in a larger patient population.
Michel
P
P
Centre for Screening and Treatment of Digestive Tumours, Clinique chirurgicale, Rouen University Hospital, France.
Paresy
M
M
Lepessot
F
F
Mauillon
J
J
Seng
S
S
Scotte
M
M
Peillon
C
C
Ducrotté
P
P
Hemet
J
J
Paillot
B
B
D000230:Adenocarcinoma / Q000473:pathology / Q000532:radiotherapy*; D000782:Aneuploidy; D001706:Biopsy; D001973:Bromodeoxyuridine / Q000627:therapeutic use; D002277:Carcinoma / Q000473:pathology / Q000532:radiotherapy; D002455:Cell Division / Q000528:radiation effects; D003110:Colonic Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D003113:Colonoscopy; D004273:DNA, Neoplasm / Q000032:analysis; D004171:Diploidy; D019583:Dose Fractionation, Radiation; D005434:Flow Cytometry; D006801:Humans; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D012004:Rectal Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D016196:S Phase / Q000528:radiation effects; D013997:Time Factors
D004273:DNA, Neoplasm; D011838:Radiation-Sensitizing Agents; D001973:Bromodeoxyuridine