Future options: the potential role of proton irradiation

Cost-effectiveness of using protons for breast irradiation aiming at minimizing cardiotoxicity: A risk-stratification analysis

Background

Incidental exposure of the heart to ionizing irradiation is associated with an increased risk of ischemic heart disease and subsequent fatality in patients with breast cancer after radiotherapy. Proton beam therapy can limit the heart dose in breast irradiation to a negligible level. However, compared with conventional photon modality, proton breast irradiation is more expensive. In this study, we performed cost-effectiveness analyses to identify the type of patients who would be more suitable for protons.

Methods

A Markov decision model was designed to evaluate the cost-effectiveness of protons vs. photons in reducing the risk of irradiation-related ischemic heart disease. A baseline evaluation was performed on a 50-year-old woman patient without the preexisting cardiac risk factor. Furthermore, risk-stratification analyses for photon mean heart dose and preexisting cardiac risk were conducted on 40-, 50-, and 60-year-old women patients under different proton cost and willingness-to-pay (WTP) settings.

Results

Using the baseline settings, the incremental effectiveness (protons vs. photons) increased from 0.043 quality-adjusted life-year (QALY) to 0.964 QALY when preexisting cardiac risk increased to 10 times its baseline level. At a proton cost of 50,000 US dollars ($), protons could be cost-effective for ≤ 60-year-old patients with diabetes and ≤50-year-old patients with grade II–III hypertension at the WTP of China ($37,653/QALY); for ≤ 60-year-old patients with diabetes and ≤ 50-year-old patients with grade II–III hypertension or ≥ 2 major cardiac risk factors at a WTP of $50,000/QALY; and for ≤ 60-year-old patients with diabetes, grade II–III hypertension or ≥ 2 major cardiac risk factors and ≤ 50-year-old patients with total cholesterol ≥ 240 mg/dL at a WTP of $100,000/QALY.

Conclusion

Patients' preexisting cardiac risk status was a key factor affecting the cardiac benefits gained from protons and should therefore be a major consideration for the clinical decision of using protons; cost-effective scenarios of protons exist in those patients with high risk of developing cardiac diseases.

Side Effects 15 Years after Lymph Node Irradiation in Breast Cancer: Randomized EORTC Trial 22922/10925

BACKGROUND

Uncertainty about the benefit/risk ratio of regional lymph node irradiation led to varying clinical protocols. We investigated long-term late side effects after internal mammary and medial supraclavicular (IM-MS) lymph node irradiation to improve shared decision-making.

METHODS

The multicentre EORTC trial (ClinicalTrials.gov, NCT00002851) randomized stage I-III breast cancer patients with involved axillary nodes and/or a medially located primary tumor. We analyzed late side effects, both longitudinally at every follow-up and cross-sectionally at 5-year intervals. All statistical tests were 2-sided.

RESULTS

Between 1996 and 2004, 46 departments from 13 countries accrued 4004 patients. Median follow-up was 15.7 years. Longitudinal follow-up data showed cumulative incidence rates at 15 years of 2.9% (95% confidence interval [CI] = 2.2%-3.8%) vs. 5.7% (95% CI = 4.7%-6.9%) (P<.001) for lung fibrosis, of 1.1% (95% CI = 0.7%-1.7%) vs. 1.9% (95% CI = 1.3%-2.6%) (P=.07) for cardiac fibrosis, and of 9.4% (95% CI = 8.0%-10.8%) vs. 11.1% (95% CI = 9.6%-12.7%) (P=.04) for any cardiac disease, when treated without or with IM-MS lymph node irradiation. There was no evidence for differences between left- and right-sided breast cancer (Wald chi-square test of treatment by breast side interaction, P=.33 and P=.35, for cardiac fibrosis and for any cardiac disease, respectively). The cumulative incidence probabilities of cross-sectionally reported side effects with a score of 2 or greater at 15 years were 0.1% (95% CI = 0.0%-0.5%) vs. 0.8% (95% CI = 0.4%-1.4%) for pulmonary (P=.02), 1.8% (95% CI = 1.1%-2.8%) vs. 2.6% (95% CI = 1.8%-3.7%) for cardiac (P=.15), and 0.0% (95% CI not evaluated) vs. 0.1% (95% CI = 0.0%-0.4%) for oesophageal (P=.16), respectively. No difference was observed in the incidence of second malignancies, contralateral breast cancer or cardiovascular deaths.

CONCLUSIONS

The incidence of late pulmonary side effects was statistically significantly higher after IM-MS lymph node irradiation, as were some of the cardiac events, without a difference between left- and right-sided treatments. Absolute rates and differences were very low, without increased non-breast cancer related mortality, even before introducing heart-sparing techniques.