The implementation of an adaptive strategy for radiotherapy, which targets the tumor more precisely, can significantly reduce the incidence of pneumonitis in patients with lung cancer, say Danish researchers.
Pneumonitis (grade 2 or greater) decreased significantly, from 50% of patients in the group treated with conventional radiotherapy to 33% in the group that received adaptive radiation treatment.
Importantly, the rates of pneumonitis were decreased without affecting the loco-regional control rate.
"This has resulted in a significant decrease in the incidence of radiation pneumonitis in patients with advanced lung cancer, while still slowing and controlling the growth of the cancer," said lead author, Azza Khalil, MD, a clinical oncologist at Aarhus University Hospital, Denmark.
Dr Khalil and colleagues presented the new findings here at the annual meeting of the European Society for Radiotherapy & Oncology (ESTRO 2017).
They explained that in conventional radiotherapy, the patient would be set up by the radiation therapist using bone structures in the chest and skin tattoos to mark the area to be treated. "We have already shown that during the course of radiotherapy the anatomical structure can differ and the cancer change position inside the chest," said Dr Khalil. "For this study, the radiation therapists used a daily [three-dimensional] image of the tumor to adjust the patient's position under the radiotherapy machine, and if they discovered any change during the course of radiotherapy, doctors and physicists were able to adapt the radiation treatment."
This method translated to targeting the tumor area more precisely and accurately, which meant leaving smaller margins so that less healthy tissue was irradiated.
Less Toxicity, No Change in Outcomes
Dr Khalil said that this adaptive strategy was introduced in their center in 2013 as a treatment for patients with locally advanced lung cancer who underwent radiation therapy with curative intent.
The team now report results from a cohort that included 108 patients who underwent radiation therapy using the adaptive strategy (ART) and a matched control group of 102 patients (noART) who were treated before April 2013.
The normal tissue constraints were similar in both groups, and patients were followed up with computed tomography every third month. Included in the analysis were the patient and tumor characteristics, details of chemotherapy that was administered, and the radiation dose.
The median follow-up time was 20 months.
The gross tumor volume was similar between groups (P = .8), but the planned target volume was significantly smaller in the ART group than in the noART group (P < .0001).
In addition, the mean lung dose of radiation was significantly lower in the ART group: mean of 12.4 Gy in ART groups vs 13.8 Gy in the noART group (P = .004).
However, the heart dose did not differ significantly between groups.
Outcomes were similar between the two groups. The rate of local recurrence was 32% in the ART group and 36% in the noART group, and the loco-regional failure rate was 45% in the ART group and 48% for controls.
The median progression-free survival times were 16 months for the ART group (95% confidence interval [CI], 13 - 20 months) and 19 months for the no-ART group (95% CI, 5 - 32 months), and the incidence of pneumonitis was significantly decreased in the ART group (P = .001).
Overall survival data are not yet mature, but thus far, they are similar between both groups: 16 months for the ART group and 19 months for the non-ART group.
"These are important findings for this group of patients who have limited treatment options," said Dr Khalil. "Adaptive radiation treatment has resulted in fewer and less pronounced pulmonary symptoms and other side effects, which makes a significant difference to the patients' quality of life."
She reported that adaptive radiation treatment has been introduced into routine clinical practice in her practice setting and that these findings can apply to clinics elsewhere.
Commenting on the study, ESTRO President Yolande Lievens, MD, who is also head of the Department of Radiation Oncology at Ghent University Hospital, Belgium, noted that this study "shows significant reductions in radiation pneumonitis when adaptive radiation treatment is used to target the tumor more precisely, and it is a good example of how we are working constantly to refine and improve radiation therapy so that patients can be treated effectively with fewer side effects."
"These are impressive decreases in toxicity, and we look forward to seeing whether overall survival for patients treated in this way is as good as or better than for patients not treated with ART," she said in a statement.
The Danish Cancer Society funded the study.
European Society for Radiotherapy & Oncology (ESTRO 2017). Abstract OC-0143. Presented May 6, 2017.