Fractionation in breast cancer

Question 1

Alphabeta ratio?

Answer 1

Alpha will represent intrinsic radiosensitivity of a cell. Beta relates to repair capacity of the cell/ sensitivity to fractionation.

Question 2

Which meta-analysis evaluated the efficacy and safety of altered radiation fraction size on outcomes for early breast cancer patients?

Answer 2

A meta-analysis from Zhou et al. 2015
Based on available evidence, HFRT with 2.5-3.0 Gy per fraction should be the better choice for treatment of early breast cancer patients.

Question 3

3 Studies about moderate hypofractionation in early breast cancer

Answer 3

Canadian trial (1993-1996)
Start A trial (1998-2002)
Start B trial (1999-2001)

Question 4

Moderate Hypofx: Canadian trial (1993-1996)

Answer 4

50/25Fx vs 42.5/16Fx
1234 patients, T1-2 N0 (by ALND), no Boost
No difference in the 10 yr DFS and OS.
Accelerated hypofractionated WBRT was not inferior to standard WBRT.

Whelan et al. NEJM 2010

Question 5

Moderate Hypofx: Start A trial (1998-2002)

Answer 5

50/25Fx vs 41.6/13Fx vs 39/13Fx over 5 weeks
2236 pts
pT1-3a, N0-1, Boost was given, locoregional RT in 14%

Breast cancer and normal breast tissues responds similarly to fraction size. No Difference in local control

Question 6

Moderate Hypofx: Start B trial (1999-2001)

Answer 6

50/25Fx vs 40/15Fx over 3 weeks
2215 pts
pT1-3a, N0-1

Conclusion: 40 gy over 3 weeks has at least as favorable control and toxicity as 50Gy over 5 weeks

Question 7

Analysis of Start A and B trials

Answer 7

Question 8

What is the long-term cardiac mortality after hypofractionated RT in breast cancer

Answer 8

The degree of hypofractionation and parasternal photon beams contributed to increased cardiac mortality in this patient cohort. Differences emerged after 12 to 15 years, indicating the need of more studies with observation time of 2 decades.

Tjessem et al. IJROBP 2013,