DVH data
Fourteen patients (70%) had V20 lung dose constraint <30%; however, in 6 (30%) V20 >30% of accepted due to the nature of the patient’s contours. The mean ipsilateral lung V5, V10, V20, V30, V40, and V50 were 39.5%, 27.8%, 22.5%, 18.7%, 15.0%, and 1.8%, respectively (Figure 7). Significant association between high V20 with decrease in FVC, FEV1, and DLCO was observed (P = 0.01, P = 0.002, and P = 0.001, respectively). Further, neoadjuvant chemotherapy was associated with decrease in DLCO at day 90 (P = 0.001).
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DISCUSSION
In our cohort, a significant reduction of FVC, FEV1, and DLCO and an association with ipsilateral lung V20 were observed at day 90 after the completion of PMRT; however, no deterioration of MMEF25–75and VO2max was observed. These results are in agreement with previously published data.12,13 An equal reduction of FVC and FEV1 with normal FEV1% pred suggests an acute exudative inflammatory process in the alveolar spaces, favoring a restrictive lung injury pattern (RIP or RIF).14 Further, unaltered MMEF25–75 supports the restrictive radiation-induced lung injury in our cohort, as deteriorated MMEF25–75 is related to damage to bronchioles leading to obstructive lung disease.15Similarly, VO2max, which is a measure of physical fitness of an individual, was found unchanged in our cohort. Possible explanation for this could be the compensation of RILT by contralateral healthy lung.16
Although we did not aim to investigate the ability of PFTs to predict the risk of RILT, but topic is still arguable, as some studies have reported that better baseline PFTs predicted lower risk of RILT, whereas some studies did not see any correlation between PFTs and RILT.17,18 Impact of PFTs to predict the risk of RILT can be explained by the few hypotheses: 1) theoretically, individuals with better baseline PFTs have relatively higher level of cellular oxygenation, thus more radiosensitivity of alveoli and more risk of RILT;19 2) on the other hand, patients with poor baseline PFTs are more likely to present with symptoms prior to radiotherapy, and in individuals with severe baseline pulmonary symptoms, the RILT score is less likely to decrease by one grade;19,20 3) as most of PFT data are available from lung cancer trials comprising patients who are mostly with emphysematous lungs. Since emphysema represents physiological missing lung parenchyma, theoretically one would expect less risk of RILT risk; and 4) physicians’ bias reduction of total dose or putting more stringent lung constraints in patients with poor baseline PFTs;21 however, further studies using the radiological data are warranted. As RILT with clinical symptoms is relatively rare (incidence <3%) and of mild nature especially with use of modern radiation therapy techniques, the treatment is oral steroids; therefore prevention (reducing lung volume and fraction size) is the key buttress.22 Further, treatment for patients with decrease in PFTs in the absence of clinical symptoms needs further investigation.
Limitations of the present study were 1) a relatively small sample size, 2) short follow-up duration, and 3) lack of correlation analysis between PFTs and RILT.
CONCLUSION
In conclusion, PFTs shall be performed in all breast cancer patients receiving PMRT for early detection of RILT as most of the patients in our cohort were asymptomatic. Studies incorporating longer duration of follow-up and large sample size are warranted to address clinical significance of PFTs in breast cancer patients receiving PMRT.
Disclosure
The authors report that no conflicts of interest in this work.
Eyad Fawzi AlSaeed,1 Faisal Khalid Balaraj,2 Mutahir A Tunio3
1Department of Radiation Oncology, Faculty of Medicine, King Saud University, King Khalid University Hospital, Riyadh, Saudi Arabia; 2Al Faisal University, Chair of Radiation Oncology, Tawam Hospital, Al Ain, United Arab Emirates; 3Radiation Oncology, Comprehensive Cancer Center, King Fahad Medical City, Riyadh, Saudi Arabia
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Source: Breast Cancer: Targets and Therapy.
Originally published May 29, 2017.
