Radio-induced lung injury: clinical and dosimetric risk factors in a subset of the CANTO RT cohort
OC-0769
Abstract
Radio-induced lung injury: clinical and dosimetric risk factors in a subset of the CANTO RT cohort
Authors: Anna Gueiderikh1, Thomas Sarrade2, Youlia Kirova3, Brigitte De La Lande4, Florent De Vathaire5, Guillaume Auzac1, Anne Laure Martin6, Sibille Everhard7, Boris Duchemann8, Rodrigue Allodji5, Sofia Rivera1
1Gustave Roussy, Radiotherapy, Villejuif, France; 2Tenon Hospital, Radiotherapy, Paris, France; 3Curie Institute Hospital, Radiotherapy, Paris, France; 4Curie Saint Cloud Hospital, Radiotherapy, Saint Cloud, France; 5Gustave Roussy, Centre for research in epidemiology and population health, Villejuif, France; 6UNICANCER, Data departement, Kremlin Bicêtre, France; 7UNICANCER, Data department, Kremlin Bicêtre, France; 8Avicenne Hospital, Pulmonology, Bobigny, France
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Purpose or Objective
Radio-induced Lung Injury (RILI) has been shown to be associated with various clinical conditions and dosimetric parameters. Former studies led to reduce radiotherapy (RT) dose to the lung and favored the discontinuation of tamoxifen during RT. However, the monocentric design and variability of dosimetric parameters chosen by those studies limited further improvement. The aim of our study was to assess the incidence of RILI in nowadays practice and to determine clinical and dosimetric risk factors associated with RILI occurrence.
Material and Methods
Data from 3 out of the 10 centers included in the CANTO-RT prospective longitudinal cohort were analysed retrospectively for RILI occurrence. This cohort included invasive cT0-3cN0-3M0 breast cancer patients from 2012 to 2018 and recorded prospectively the occurrence of treatments side effects by questionnaires and medical visits at the end of treatments and up to 60 months after. Dosimetric data and RT planning CT scans with contoured volumes were available for all patients. We considered V5Gy, V10Gy, V15Gy, V20Gy, V25 Gy, V30 Gy, V35 Gy, V40 Gy and Dmean to the homolateral lung. RILI events were defined in all patients by the association of clinical symptoms and compatible medical imaging.
Results
Within the 5 first years afterRT, RILI was found in 38/1565 (2.4%) patients. Grade 2 RILI represented 15/38 events (39%) and 2/38 events (6%) were grade 3 or 4. There were no grade 5. The incidence of ≥ grade 3 events was 0.1% of the total cohort, confirming favourable safety profile of breast radiotherapy in CANTO.
Treatment was performed mainly in conformational 3D RT (96%). In an univariate analysis, we confirmed the association of RILI occurrence with pulmonary medical history, chemotherapy use, nodal RT. All dosimetric parameters were highly correlated and had close predictive value but the V30Gy was the most predictive of RILI occurrence in our dataset (ROC curve AUC=0.68). In the multivariate analysis, only pulmonary medical history (OR=2.2, p=0.02) and high V30Gy (OR=2.05, p=0.04) remained predictive factors for RILI occurrence. The best threshold for V30Gy in our study was V30Gy < 13%. We confirmed the data from Lee and al. 2020, showing that V30Gy < 10% would have a better predictive value than V30Gy<20%.
We noted that RILI occurrence was often poorly identified. Pulmonary medical history associated with RILI occurrence were mainly COPD, infectious pneumonitis or interstitial syndrome. On the contrary, the RILI group presented less cardiac medical history.
Conclusion
Our study confirms the pulmonary safety of breast 3D RT in CANTO RT, with an incidence of ≥ grade 3 RILI of 0.1% and all grade RILI of 2.4%. Further analysis in large cohorts with modern radiotherapy techniques such as IMRT are needed. Our results argue in favour of a dose constraint to the ipsilateral lung using the threshold of V30Gy<10-13%, especially in patients presenting pulmonary medical history. Pulmonary disease record should be taken into account for RT planning.