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Purpose The Clinical Evaluation of Pertuzumab and Trastuzumab (CLEOPATRA) study showed a 15.7-month survival benefit with the addition of pertuzumab to docetaxel and trastuzumab (THP) as first-line treatment for patients with human epidermal growth factor receptor 2 (HER2) –overexpressing metastatic breast cancer. We performed a cost-effectiveness analysis to assess the value of adding pertuzumab. Patient and Methods We developed a decision-analytic Markov model to evaluate the cost effectiveness of docetaxel plus trastuzumab (TH) with or without pertuzumab in US patients with metastatic breast cancer. The model followed patients weekly over their remaining lifetimes. Health states included stable disease, progressing disease, hospice, and death. Transition probabilities were based on the CLEOPATRA study. Costs reflected the 2014 Medicare rates. Health state utilities were the same as those used in other recent cost-effectiveness studies of trastuzumab and pertuzumab. Outcomes included health benefits expressed as discounted quality-adjusted life-years (QALYs), costs in US dollars, and cost effectiveness expressed as an incremental cost-effectiveness ratio. One- and multiway deterministic and probabilistic sensitivity analyses explored the effects of specific assumptions. Results Modeled median survival was 39.4 months for TH and 56.9 months for THP. The addition of pertuzumab resulted in an additional 1.81 life-years gained, or 0.62 QALYs, at a cost of $472,668 per QALY gained. Deterministic sensitivity analysis showed that THP is unlikely to be cost effective even under the most favorable assumptions, and probabilistic sensitivity analysis predicted 0% chance of cost effectiveness at a willingness to pay of $100,000 per QALY gained. Conclusion THP in patients with metastatic HER2-positive breast cancer is unlikely to be cost effective in the United States.

132 Background: Sinoatrial node (SAN) injury following stereotactic ablative radiation therapy (SABR) in the chest has not been reported in the literature. We report SAN dysfunction as a potential toxicity of SABR in the chest. Methods: We examined the clinical courses and SABR plans of 47 patients treated for T1 or T2 non-small cell lung cancer of the right upper lobe, middle lobe, lower lobe, or hilum. After developing a contouring atlas for the SAN, based upon the junction between the superior vena cava and the right atrium, dose to the SAN was retrospectively determined for each patient. We identified 13 patients whose treatment imparted significant dose to the SAN, as defined by the SAN encompassed within the 10% prescription isodose (IDL) line. Biologically effective doses (BED), acute and chronic, were correlated with SAN toxicity. Results: Patients underwent SABR to the right lung to a dose of 40-50 Gy in 4 or 5 fractions, with mean acute BED (alpha/beta ratio = 10) of 100.2 Gy and late BED (alpha/beta ratio = 3) of 222.7 Gy. Mean volume of the GTV and PTV were 26.1 and 75.1 mL, respectively. Mean follow-up was 25.5 months. The mean volume of the SAN was 0.37 mL. Average max dose and mean dose to the SAN were 24.7 and 70.7 Gy, respectively. Of the 13 patients whose treatment imparted significant dose to the SAN, one patient without prior arrhythmia developed symptomatic SAN dysfunction requiring pacemaker placement at 6 months after completion of treatment. The sinoatrial node of the patient received a maximum dose of 44.8 Gy in 4 fractions, correlated with an acute BED (alpha/beta ratio = 10) of 90 Gy and late BED (alpha/beta ratio = 3) of 194.1 Gy, and a mean dose of 35.5 Gy in 4 fractions, correlated with an acute BED (alpha/beta ratio = 10) of 71 Gy and late BED (alpha/beta ratio = 3) of 153.8 Gy. This was the third highest max dose and second highest mean dose to SAN in the cohort. Conclusions: We report sinoatrial node dysfunction as a potential toxicity of SABR in the chest for non-small cell lung cancer. Caution is advised when treatment imparts significant dose to the sinoatrial node.

e18082Background: Studies have shown that socioeconomic (SE) disparities contribute to differences in cancer survival, with patients in lower SE classes consistently having poorer survival compared...

201 Background: Various schedules of palliative radiotherapy (pRT) are prescribed for metastatic breast cancer (MBC) patients. Length of treatment can vary from a single day to three weeks. Single fraction pRT provides similar pain relief vs. multi-fraction pRT for bone metastases, but retreatment rates are higher. In the era of targeted and hormonal therapy, patients with MBC can survive many years after their initial diagnosis. We investigated whether patients with MBC who were prescribed single fraction pRT had poorer prognoses and experienced shorter survival than patients who were prescribed multi-fraction pRT. Methods: Patients at a single institution with MBC underwent pRT, with fractionation schedules including 8 Gy in 1 fraction (fx), 20 Gy in 5 fx, 30 Gy in 10 fx, 37.5 Gy in 15 fx between 2001-2015. 392 treatments were prescribed (109/241/29/13 in each regimen as above). Date of death was obtained from medical records, Social Security Death Index, or published obituaries. Patients who were alive or whose date of death could not be determined were censored at the date of their last encounter. Survival was calculated from the start of treatment to the date of death or censorship. Results: Patients treated with 37.5 Gy in 15 fx (MS 20 months, p = 0.002) or 30 Gy in 10 fx (MS 22 months, p = 0.03) experienced longer survival than patients treated with 8 Gy in 1 fx (MS 8 months). There was no significant survival difference between patients treated with 20 Gy in 5 fx (MS 18 months, p = 0.49) and patients treated with 8 Gy in 1 fx. There was no significant survival difference between patients treated by the three multi-fractionation schedules. Conclusions: MBC patients who were prescribed 37.5 Gy and 30 Gy lived longer than patients who were prescribed 8 Gy of pRT. No statistically significant difference was found between patients who were prescribed 20 Gy compared to 8 Gy, possibly due to the lower number of patients who received these regimens. Single fraction pRT was more likely to be prescribed to patients who would ultimately have shorter survival. More research is needed, ideally across multiple institutions, to explore the correlation between physician estimation of patient survival and selection of pRT regimen for patients with MBC.

6047 Background: To determine whether total lesion glycolysis (TLG) measured during radiation for locally advanced oropharyngeal cancer (OPC) correlates with outcomes. Methods: Patients with Stage ...