Concepts

Question 1

How does TI (Therapeutic Index) relate to drug safety?

Answer 1

Larger the TI, the safer the drug

Smaller the TI, less safe the drug; must be more careful have to be with dosing

Question 2

What advantages do alpha-emitters have over beta-emitters as radiopharmaceuticals?

Answer 2

Alpha emitters: short path length, can target individual cancer cells

Beta emitters: wider path length, less specificity, more tox

Question 3

What critical needs do alpha-emitters address in cancer therapy?

Answer 3

Potential to eradicate disseminated tumor cells or sub-population of tumor stem cells.

This requires:

1. A systemic targeted therapy
2. Minimally susceptible to chemo- or radio-resistance
3. Potent enough to sterilize individual cells and microscopic tumor clusters
4. Acceptable tox profile

Question 4

What radiation qualities are needed for accurate dosimetry calculations?

Answer 4

Activity distribution as a function of time (at cellular and subcellular level)

Question 5

How is activity distribution measured in vitro?

Answer 5

1. Uptake on the cell surface (or within the cell)

2. Known fraction in the surrounding solution

Question 6

How is activity distribution determined clinically?

Answer 6

1. Modeling 3D geometry of spheroid (or tissue geometry determined by microscopic tissue biopsy samples)
2. Mathematic modeling of carrier molecules diffusing through tissue and binding to cell surface

Question 7

When do you use Gray (Gy) over Sievert (Sv) in radiation studies?

Answer 7

Deterministic effects are conventionally compared to values of absorbed dose expressed by the SI unit gray (Gy)

Sievert (Sv) implies that only stochastic effects are being considered

Question 8

Units used to measure specific activity

Answer 8

Becquerel (Bq)
Curie (Ci)
Rutherford (Rd)

Question 9

Units used to measure absorbed dose

Answer 9

Gray (Gy)
Erg per gram (Erg/g)
Rad