Radiation heart dosimetric parameters do not affect survival in NSCLC patients undergoing PORT
Radiation heart dosimetric parameters (RHDPs) appear to exert neutral effect on overall survival (OS) in nonsmall cell lung cancer patients undergoing postoperative thoracic radiotherapy (PORT), according to a recent Singapore study.
“In summary, there is insufficient evidence to conclude that RHDPs are associated with OS for patients with NSCLC treated with PORT,” said researchers. “This finding is promising despite the small sample size and relatively short follow-up. The patients in PORT cohort were likely very well-selected given that they were fit enough to undergo surgery.”
In the 43 included patients (median age, 63.6 years; 58 percent female) followed for a median of 36.6 months, 95 percent had good performance status, as assessed by the Eastern Cooperative Oncology Group. Majority were never smokers (67 percent) and did not have pre-existing chronic obstructive pulmonary disease (98 percent). [Medicine 2019;98:e17020]
A total of 27 deaths were reported, with a median survival of 23.4 months. The resulting 2-year and 5-year OS estimates were 65 percent and 34 percent, respectively.
Univariate Cox regression analysis identified age at lung cancer diagnosis as the only potential risk factor associated with OS, such that older participants were significantly more likely to die than their younger counterparts (hazard ratio [HR], 1.06, 95 percent CI, 1.01–1.10; p=0.008). Having a malignancy with a squamous cell histology was also a possible risk factor but only of marginal significance (HR, 2.69, 0.97–7.50; p=0.058).
Notably, the different RHDPs included in the study were of no particular importance in the context of survival. For instance, mean heart dose was not significantly associated with OS (HR, 0.99, 0.94–1.04; p=0.817), and neither were the dose to 30 percent of heart volume (HR, 1.00, 0.96–1.03; p=0.918) and mean lung dose (HR, 0.98, 0.88–1.09; p=0.705).
Similarly, the heart volumes that received ≥5 Gy (HR, 1.00, 0.98–1.01; p=0.551), ≥25 Gy (HR, 1.00, 0.97–1.02; p=0.780), ≥30 Gy (HR, 1.00, 0.97–1.03; p=0.855), ≥40 Gy (HR, 1.00, 0.96–1.04; p=0.975) and ≥50 Gy (HR, 1.01, 0.93–1.09; p=0.868) were all unrelated to the risk of death. The same was true for the lung volumes that received ≥5 Gy (HR, 0.99, 0.97–1.02; p=0.655) and ≥20 Gy (HR, 0.98, 0.93–1.03; p=0.393).
“[N]o prior study [has been conducted] to assess the relationship between RHDPs and OS in NSCLC patients who received PORT. Our study found that various RHDPs were not significantly associated with OS,” said the researchers, however pointing out that the present sample size was small and may not be exactly representative of the entire population.
“Studies with larger sample size and longer-term follow-up are needed to assess AMI outcome, given the possibility of late occurrence of AMI events,” they noted, adding that there is also a need for future efforts to identify the specific and relevant RHDPs that lead to cardiac toxicity and even death in patients undergoing PORT.