The small intestine is unavoidably included in pelvic
irradiation fields. The dose limiting normal tissue reactions
in the intestine are therefore of clinical importance.
Hyperfractionation has been advocated to improve local
tumor control by increasing radiation dose [
1],[
2],[
6]. There
are clinical studies of hyperfractionation on rectum cancer
and most of them advocate the benefits of hyperfractionation
[
4],[
6],[
7].
There are also experimental studies that investigate effects
of fractionation on the intestine. Brennan et al. [8]
compared the responses of small intestinal morphological
parameters after acute and protracted doses of radiation.
Mice were examined 6, 24, and 72 hours after whole body
gamma irradiation, given either as an acute 5 Gy dose, or
as a protracted (continuous) dose of 20 cGy per day for
25 days to a total dose of 5 Gy. At 72 hours histological
assessment revealed ultra structural changes more often in
the single 5 Gy fractionation schedule.
Saclarides [9] reported radiation injuries of the gastrointestinal
tract. During the acute phase of injury, characteristic
changes are usually confined to the mucosa and
include crypt cell damage, inflammatory cell infiltrate,
mucosal slough, and loss of crypts. This study reported
that these microscopic findings might still be present
three months after therapy.
Hauer-Jensen and Langberg [3],[5],[10]-[14] had a series
of studies on the effects of time-dose-fractionation on rat
small intestine. These studies showed that reduced overall
irradiation time and increased fraction size greatly
increased the frequency of intestinal complications, as
well as histopathologic radiation injury. Epithelial damage
was markedly increased in groups with shorter overall
irradiation time. As evident from comparison of the
regimens with 5.6 Gy fractions with the regimens with
2.8 Gy twice daily fractions, it was demonstrated that hyperfractionation
reduced damage in all structures of the
intestine [13]. Langberg et al. [14] noted that increasing
the interfraction interval from 0 to 6 hours was associated
with a statistically significant reduction in intestinal complications
(from 53% to 0%, p <0.001).
Most of the experimental studies designed to show
time-dose-fractionation effects on small intestine were
with greater fractionation sizes and shorter overall treatment
duration than normally used for treatment in men.
So we planned to study the effects of exact pure hyperfractionated
schedule over small intestine both clinically
and morphologically.
In the weight evaluation the hyperfractionated group
had a significantly longer weight loss period. Histopathologically,
villous length and mitotic figure counts were
statistically different compared to the control's but there
were no differences in means between the two irradiation
schedules for quantitative parameters. When compared
with respect to the qualitative parameters, again there were
no statistical differences between irradiation groups.
So as a conclusion, hyperfractionated pelvic irradiation
was tolerated but weight loss lasted longer. There was no
difference in terms of histopathological evaluation. This
might be explained by the histopathological evaluations
being made five weeks after the last day of irradiation.
According to our results hyperfractionated irradiation was
applied with tolerable significantly higher clinical toxicity
but the difference was not significant histopathologically
at the 5th week of follow up. It would be useful to study
the subacute and chronic histopathological alterations and
the tumor responses in the same irradiation schedules.
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