Biochemical signs of impaired cobalamin status during and after radiotherapy for rectal cancer.
OBJECTIVE
The aim of the study was to investigate whether pelvic radiotherapy for rectal cancer had a negative impact on cobalamin status.


METHODS
Consecutive patients receiving pelvic radiotherapy (50 Gy) for rectal cancer were evaluated prospectively (n = 54). Serum cobalamin, holotranscobalamin (holoTC), methylmalonic acid (MMA), and total homocysteine (tHcy) were measured at start and end of radiotherapy, at follow-up 4-6 weeks and 1 year (n = 23) after radiotherapy.


RESULTS
Mean serum cobalamin decreased from 306 pmol/L before treatment to 267 pmol/L at the end of radiotherapy (p < 0.001), 247 pmol/L 4-6 weeks after radiotherapy (p < 0.001), and 249 pmol/L 1 year after radiotherapy (p = 0.02). Mean serum MMA was 0.16 micromol/L pretreatment, 0.17 micromol/L at the end of radiotherapy (n.s.), and increased to 0.19 micromol/L after 4-6 weeks (p = 0.007), and to 0.21 micromol/L after 1 year (p < 0.001). There was no change in serum tHcy. Mean serum holoTC was reduced from 111 pmol/L pretreatment to 93 pmol/L 4-6 weeks after radiotherapy (p = 0.002).


CONCLUSIONS
The data suggest rapid and persistent decrease in cobalamin status after radiotherapy for rectal cancer, as reflected by reduced serum cobalamin combined with increased serum MMA. This observation, though modest, may motivate routine monitoring of cobalamin status at follow-up after radiotherapy.
Department of Oncology, Ullevaal University Hospital, Oslo, Norway.
Marianne Grønlie
MG
Guren
Jørn
J
Schneede
Kjell Magne
KM
Tveit
Per Magne
PM
Ueland
Ebba
E
Nexø
Svein
S
Dueland
D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D003967:Diarrhea / Q000097:blood; D005260:Female; D006711:Homocystine / Q000097:blood; D006801:Humans; D008297:Male; D008764:Methylmalonic Acid / Q000097:blood; D008875:Middle Aged; D012004:Rectal Neoplasms / Q000097:blood* / Q000532:radiotherapy* / Q000601:surgery; D014155:Transcobalamins / Q000378:metabolism; D014805:Vitamin B 12 / Q000097:blood*; D014806:Vitamin B 12 Deficiency / Q000209:etiology
D015415:Biomarkers; D014155:Transcobalamins; D006711:Homocystine; D008764:Methylmalonic Acid; D014805:Vitamin B 12