Breast Clinical Session: IMRT

Adjuvant RT in Breast Cancer

Adjuvant RT in subgroups

Conventional Planning : Principles

1. Beam arrangement for breast - tangential
2. Proper selection of medial and lateral entry points
3. Properly matched posterior edge to avoid divergence to contralateral breast
4. Keep CLD between 1 - 2 cm.
5. Properly matched regional nodal fields

Why use IMRT

1. Dose homogenization
2. Integrated Boost
3. Partial breast irradiation

Earliest Breast IMRT Trial

Change in breast appearance risk reduced by 1.7 times ! Significantly fewer clinical induration.

Field in field IMRT

Image from Mukesh MB JCO 2013

Simultaneous Integrated Boost

Import HIGH

Partial Breast Irradiation

This trial compared standard WBI with tangents (with a electron en face boost) versus a 5 field coplanar fixed field step and shoot IMRT technique for PBI

Partial Breast Irradiation

Import Low Results

No difference in breast tumor recurrrence endpoints.

Import Low results

Lower complication rates in PBI arm.

Example Dose constraints (HYPORT)

Chatterjee et al Trials 2020

Adherence to constraints (Heart)

Courtesy Chatterjee et al : Presented in ESTRO 2024 on behalf of the HYPORT Adjuvant Trialist’s group

Adherence to constraints (Lung)

Courtesy Chatterjee et al : Presented in ESTRO 2024 on behalf of the HYPORT Adjuvant Trialist’s group

Take Home

• Breast IMRT has a wealth of evidence for application

• Inverse planned IMRT is typically not necessary unless complex regional nodal RT is required.

• Adjuvant Breast radiotherapy using IMRT should be planned carefully keeping in mind contralateral breast / lung doses.