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Bone marrow function – effects of chemotherapy

Storage compartment exists

Supplies cells to PB for 8-10 days

Events in PB lag 7days behind BM

Day 9-10 fall in PB counts

Nadir-Day 14-18

Recovery –Day 21

Completed recovery – Day 28

Chemotherapy effects

Cell death can be due to direct effect

Agent may trigger differentiation

May cause apoptosis (programmed cell death)

Cell death may not take place at time of drug exposure

Only a proportion of cells die

Chemotherapy-assumptions

All tumor cells are equally sensitive

Drug accessibility and sensitivity-independent of location of cells and host factors

Cell sensitivity remains constant

Evidence to the contrary

Tumor growth – depends on:

Cell cycle time

Growth fraction

Total number of tumor cells

Intrinsic cell death

Phases in cell cycle

G0 – resting

G1 – RNA and protein synthesis

S – DNA synthesis

G2 – RNA and protein synthesis

M – Mitosis

As cells mature they differentiate (BM, GIT cells – cell cycle 24-48 hrs)

Thus their sensitivity to chemotherapy

Phase and cell cycle specificity of drugs

Phase specific drugs

Cell cycle specific

Cell cycle non-specific

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