The present study sought to characterize the initial experience of a single-room integrated proton therapy center opened within an existing comprehensive cancer center at an academic teaching hospital in a major metropolitan area with particular focus on the spectrum of disease sites treated, the utilization of systemic therapies, the geographic reach, and the impact of insurance approval on treatment times.
From a geographic standpoint, the installation of the proton center drew in patients largely from the surrounding areas within Washington, DC, Virginia, and Maryland, although a small number of patients traveled from out of state or internationally for treatment. This increase in geographic outreach allowed the facility to reach treatment capacity within six months of operation. This influx of patients from the surrounding areas also allowed for the facility to maintain the current x-ray treatment volume.
A surprisingly diverse group of disease sites were treated during the first 16 months of operation. Tumors of the central nervous system were the most common malignancy treated, primarily comprised of gliomas, followed by meningiomas and pituitary adenomas. This was largely driven by the need to reduce doses to the surrounding normal brain and critical OARs, such as the optic apparatus and brainstem, to minimize late effects of radiation treatments, including neurocognitive decline (24, 32). Moreover, primary malignancies of the CNS constituted the largest proportion of the reirradiation cases treated at our institution. Reirradiation of the brain is uniquely challenging given patients have often previously undergone surgery, chemotherapy and high dose radiation therapy, and are thus more susceptible to tissue damage (24, 33).
For decades, proton centers have focused on treatment of tumors of the CNS due to its inherent lack of motion, tissue homogeneity, and reproducible setup. At our institution, we wanted to expand into other, more challenging sites including the thorax and gastrointestinal tract, in order to explore more novel uses of the available technology. As such, one-third of all patients treated were diagnosed with either thoracic or GI malignancies. Proton beam radiotherapy was utilized primarily for definitive treatment of esophageal cancer and thoracic malignancies to minimize dose delivered to the lungs, heart, and spinal cord. This was especially important in patients undergoing reirradiation where PBT was utilized to better spare the previously irradiated spinal cord. The ability of PBT to decrease heart dose and spare various cardiac substructures has been well established in numerous dosimetric studies and, clinically, increasing heart doses have been shown to have a negative impact on overall survival (34–37). The physical characteristics of PBT providing additional normal tissue sparing also allowed for dose escalation within the liver for treatment of primary intrahepatic malignancies, which has demonstrated high rates of local control in patients with both hepatocellular carcinoma and intrahepatic cholangiocarcinomas (26). Patients treated with PBT for thymomas have also been shown to have excellent outcomes with significant dosimetric advantages in reducing doses to surrounding critical structures which have been shown to decrease rates of both early and late toxicities (38, 39). This can be especially important given the younger age of patients diagnosed with thymomas and the long natural history of the disease in treated patients.
Incorporation of particle therapy at our pre-existing NCI designated comprehensive cancer center was critical to allow access to our multidisciplinary team, including medical oncology, surgical oncology and advanced inpatient care. Half of our patients were able to be treated with chemotherapy during PBT treatments without the logistical challenges of transportation to the main academic center. Access to advanced oncologic multidisciplinary teams allowed for seamless integration of PBT into standard of care practices as well as clinical trial enrollment for patients at the same cancer center (20, 40, 41). The addition of PBT at the main campus also allowed for easier and cost-effective integration of the existing simulator and radiation clinical staff, which enabled uninterrupted oncologic care with transitions between x-ray and proton therapies for planned combined modality therapy or machine maintenance.
One significant challenge continues to be insurance coverage for PBT. Initially published in 2014 and recently updated and expanded in 2017, ASTRO reported a model policy list of expert recommended indications for insurance coverage of PBT (31). However, insurers have yet to fully implement these expert consensus recommendations. Twenty percent of our patients ultimately treated with PBT were initially denied for insurance coverage despite all patients qualifying for either ASTRO model policy groups 1 or 2. These insurance denials resulted in significant resource cost to the department, including numerous physician peer-to-peer discussions, advocacy letters, and comparison x-ray versus proton plans for treatment rationalization. More importantly, the insurance denials resulted in significant delays in patient care with most patients delayed by at least one month prior to their first treatment. Our results are in line with recently published experiences from MD Anderson where a significant number of patients were denied PBT coverage by private insurance with a subsequent approval process that required a similar significant time and resource investment from the radiation department (42). The appeal process, as demonstrated by other institutions, also leads to significant delays to the start of proton treatment, with adult patients waiting an average of one month (42, 43). Treatment delays have been previously demonstrated across various subsites to be detrimental to patient outcomes, including for gynecologic cancers and tumors of the head and neck (44–46). Another potential complication from extensive treatment delays is increased psychological stress to patients resulting in increased anxiety and depression, which has been anecdotally seen at our institution. These delays may reduce patient compliance with prescribed treatments and adversely impact their treatment outcomes (47, 48).
Limitations of the present study include its retrospective nature and the fact that the analysis only included patients that ultimately received PBT. There may have been patients who would have benefitted from PBT but were denied treatment by insurance or not pursued due to expected insurance denial and subsequent treatment delays. Further investigation into insurance denial patterns and approval rates across all patients is warranted. Additionally, this was a single-institutional analysis in a metropolitan area, which may limit the generalizability of our experience to other centers. Nevertheless, our results mirror other published experiences which suggests that there may be some general applicability to other centers across the country (43, 49).
In conclusion, a single room active scanning proton therapy treatment center provides a viable option for institutions preparing to invest in particle therapy. Incorporation of PBT into an established cancer center allowed for seamless integration of particle therapy into the multidisciplinary oncologic treatments of patients. Following installation of a single room proton center, 132 patients were treated during the first 16 months of operation spanning a wide variety of disease sites, most commonly tumors of the central nervous system, gastrointestinal tract, and genitourinary tracts. Insurance approval for PBT continues to be a resource and time intensive process for patients and providers, and improvements are needed to provide more timely access to necessary cancer care.