What are the oesophagus dosimetric constraints during breast cancer hypofractionated radiotherapy?
PO-1563
Abstract
What are the oesophagus dosimetric constraints during breast cancer hypofractionated radiotherapy?
Authors: Fatma Dhouib1, Maiem Frikha2, Nejla Fourati3, Zied Fessi3, Leila Farhat3, Wafa Mnejja3, Jamel Daoud3
1Habib Bourguiba University Hospital, oncology-radiotherapy, Sfax, Tunisia; 2Habib Bourguiba University Hospital, oncology-Radiotherapy, Sfax, Tunisia; 3Habib Bourguiba University Hospital, Oncology-radiotherapy, Sfax, Tunisia
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Purpose or Objective
Hypofractionated
radiotherapy (HRT) is becoming a valid option in the treatment of breast
cancer. However, data are missing concerning the normal tissues dosimetric
constraints. The purpose of this study is to evaluate the cumulative
doses in the oesophagus during HRT for breast cancer with a clinical toxicities
correlation in order to propose dosimetric constraints adapted to this type of
fractionation.
Material and Methods
This is a
retrospective study analyzing the dosimetric plans of 41 patients treated with
adjuvant locoregional (LR) radiotherapy for localized breast cancer between
January and December 2020. The treatment plan was carried out according to a
three dimensional (3D) conformational technique. The total dose prescribed was
42.5 Gy in 16 fractions with a boost of 10 Gy in 4 fractions in the tumor bed
in case of a conservative treatment (35%) and 40 Gy in 15 fractions in case of
a radical treatment (65%) at a rate of 5 fractions per week. The whole esophagus
was delineated. By analyzing the dose-volume histogram, we retrospectively
recorded the mean dose (Dmean), the maximum dose (Dmax), the volume receiving
more than: 17 Gy (V17) , 30 Gy (V30) and
35 Gy (V35). These dosimetric constraint levels were defined by calculating the
biological equivalent dose. Clinical assessment of esophageal toxicity was performed
at the end of the radiotherapy sessions and 6 months later, using a
questionnaire based on the RTOG clinical scales. Data analysis was performed by
SPSS version 20.
Results
The median
of Dmean, Dmax, V17, V30, and V35 were respectively of 4.14Gy [0.8-12.85], 37Gy
[2.5-43], 8% [0-33.87], 2.2% [0-25.7] and 0.02% [0-18.26]. The 3rd
quartile (Q3) of Dmean, Dmax, V17, V30 and V35 were respectively of 7.3 Gy, 39
Gy, 18.3%, 9% and 2.7%.
The
following table summarizes the data of the cumulative doses in the oesophagus:
At the end
of radiotherapy sessions, seven patients (17.07%) have reported a radiation-induced
esophagitis (garde 1 in 6 cases and grade 2 in only one case). Of these seven patients,
the Dmax in the oesophagus was >
35 Gy in 6 cases and >
38 Gy in 5 cases. At six months after the end of the radiotherapy, no patient
had clinical signs of esophagitis.
Conclusion
Radiation-induced
esophagitis is one of the most underestimated complications in locoregional
treatment of localized breast cancers. In the absence of radiation-induced
esophagitis prevention guidelines, we propose a systematic delineation of the
whole esophagus in case of LR HRT in order to minimize as much as possible the cumulative
doses at its level. The results of this study show that these constraints could
be reasonable to respect during dosimetric optimization: Dmean <= 8 Gy, Dmax
<= 38 Gy, V17 <= 19% and V30 <= 9%. However, these
results should to be confirmed by larger series.