Tissue repair capacity and repair kinetics deduced from multifractionated or continuous irradiation regimens with incomplete repair

Br. J. Cancer, 1984 · DOI: · Published: January 1, 1984

Oncology Regenerative Medicine & Stem Cells

Simple Explanation

The paper proposes a model to understand cell survival after multiple radiation doses when there isn't enough time between doses for cells to fully repair themselves. This model can be adapted to predict tissue responses to radiation treatments where repair is incomplete, leading to a curved relationship between the total dose and dose per fraction. Studying tissue responses to radiation with incomplete repair or continuous exposure allows for the estimation of both repair capacity and repair kinetics.

Study Duration

Not specified

Participants

Mouse, rat

Evidence Level

Not specified

Key Findings

1
Repair halftimes in mouse tissues (jejunum, colon, bone marrow) ranged from 0.3-0.9 hours, with β/α values around 0.1 Gy-1.
2
Mouse lung tissue showed a repair halftime of 1.5 hours and a β/α value of 0.27 Gy-1.
3
Rat spinal cord had a β/α value of 0.7 Gy-1 and a repair halftime of 1.5 hours.

Research Summary

The study proposes a model to explain cell survival after multiple radiation doses when complete repair doesn't occur between doses, which transforms into an accumulation model for continuous irradiation. Analyzing tissue responses to multifractionated regimens with incomplete repair or continuous exposures helps determine both repair capacity and repair kinetics, reducing the impact of regeneration on results. The results from mouse and rat tissues suggest that early and late-responding normal tissues differ in both repair capacity and kinetics, implying that hyperfractionation benefits may be limited by slower repair rates in late-responding tissues.

Practical Implications

Improved Radiotherapy Schedules

Understanding tissue repair kinetics could lead to optimized radiation schedules that spare late-responding tissues.

Hyperfractionation Limitations

The slower repair rate in late-responding tissues may limit the benefits of hyperfractionated radiotherapy.

Predictive Modeling

The proposed model can be used to predict tissue response to different radiation regimens, improving treatment planning.

Study Limitations

1
The model relies on accurate determination of the log number of clonogens.
2
Inconsistencies in pooled data, such as cell-cycle redistribution, can affect the model's accuracy.
3
Other factors, such as slow repair, could also contribute to the observed curvature in dose-response graphs.

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