# DOSE-TIME-FRACTIONATION IN CNS RADIATION TOLERANCE

> **NIH NIH R01** · UNIVERSITY OF CALIF-LOS ALAMOS NAT LAB · 1987 · $105,387

## Abstract

The tolerance of critical normal tissues is often dose limiting in clinical
radiotherapy.  Tolerance doses are only relatively well known for
conventional fractionation schemes.  With the use of higher doses per
fraction (3 Gy or more), more severe late complications occurred as was
predicted on basis of acute effects.  Decreasing the fractional doses below
the conventional dose of 2 Gy resulted in a greater increase in tolerance
for late effects as for acute effects.  These observations provide a basis
for an improvement of cancer therapy by, e.g., multiple daily
fractionation.  However, before any new treatment scheme can be implemented
in the clinic, quantitative information should be available on the
tolerance of critical normal tissues, such as the central nervous system
(CNS).

Experimental studies on time-dose relationships in the rat spinal cord have
shown an excellent correlation with observations in the human CNS.  Similar
to the human brain, early (6 months) and late (8-18 months) waves of
delayed damage have been observed in the rat cervical spinal cord, both of
which are clinically relevant.  The repair and regeneration characteristics
of the target cells involved are different, but both show a large capacity
for repair of subeffective radiation damage.

The development of these well-defined endpoints will be studied on the
following aspects:  a) effect of decreasing fraction-size on the total
effective dose, b) the kinetics of repair of sublethal damage as a function
of fraction size, c) long-term recovery of residual damage, and d)
dependence of the effective dose on the irradiated volume.

## Key facts

- **NIH application ID:** 3173814
- **Project number:** 7R01CA036267-04
- **Recipient organization:** UNIVERSITY OF CALIF-LOS ALAMOS NAT LAB
- **Principal Investigator:** MUDUNDI R RAJU
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1987
- **Award amount:** $105,387
- **Award type:** 7
- **Project period:** 1987-08-01 → 1988-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3173814

## Citation

> US National Institutes of Health, RePORTER application 3173814, DOSE-TIME-FRACTIONATION IN CNS RADIATION TOLERANCE (7R01CA036267-04). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3173814. Licensed CC0.

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