Aparna Suryadevara1, Yakub Mohmd2, Akkineni Naga Prasanthi3
BACKGROUND
Breast cancer is the most common cancer among Indian women and adjuvant
radiation is an integral part of its management. Adjuvant radiation can be planned
by 2D conventional or conformal technique. The most common technique has been
2D technique worldwide, especially in high volume, low resource settings. The
comparison of 2D and conformal techniques for chest wall and lymph nodal areas
among breast cancer patients is sparse in the literature. The purpose of our study
was to dosimetrically compare the 2 D conventional and field-in-field intensity
modulating radiational therapy (FiF IMRT) technique in adjuvant radiation to chest
wall + / - SCF / axilla areas at Basavatarakam Indo-American Cancer Hospital and
Research Institute.
METHODS
This is a single institute cross sectional study. During immobilisation for planning
and CT scan, external radio-opaque markers were placed over chest wall. After
contouring and planning by FiF IMRT technique, 2D conventional plan was done
by placing MT, LT fields + / - SCF by SSD technique with the guidance of the
markers placed and both plans were compared by the dose-volume histogram
(DVH) analysis.
RESULTS
The planning target volume (PTV) coverage was lower with the 2D plan but the
advantage of the 2D plan was, it showed lower OAR compared to FiF IMRT plan.
The studies comparing PTV coverage and OAR doses between 2D and conformal
techniques were mostly done in BCS patients and similar studies for chest wall
radiation are rare in the literature and with conflicting results and different
methods of 2D planning with modification of 2D plans than what is done routinely.
Our study used the 2D plan by SSD technique and also manual MU calculation
without normalisation of the plan to the contoured PTV, unlike other studies to
minimise the deviation in 2D plan and hence, the comparison of the PTV or OAR
doses with FiF IMRT plans.
CONCLUSIONS
The 2D plan for chest wall planned by tangential fields has the disadvantage in
being less homogenous and conformal but with much lower OAR doses than FiF
IMRT. It is a safe to treat as far as OARs are considered.
