Proton Therapy Updates
January 2020

Towards fast and robust 4D optimization for moving tumors with scanned proton therapy

Medical Physics 2019

Purpose: Robust optimization is becoming the gold standard for generating robust plans against various kinds of treatment uncertainties.

Today, most robust optimization strategies use a pragmatic set of treatment scenarios (so-called uncertainty set) consisting of combinations of maximum errors, of each considered uncertainty source (such as tumor motion, setup and image-conversion errors). This approach presents two key issues.

First, a subset of considered scenarios is unnecessarily improbable which could potentially compromise the plan quality.

Second, the resulting large un certainty set leads to long plan computation times, which limits the potential for robust optimization as a standard clinical tool. In order to address these issues, a method is introduced which is able to pre-select a limited set of relevant treatment error scenarios.

Proton therapy for non-small cell lung cancer: the road ahead

Translational Lung Cancer Research 2019

Proton therapy is an evolving radiotherapy modality with indication for numerous cancer types. With the benefits of reducing dose and sparing normal tissue, protons offer a clear physical and dosimetric advantage over photon radiotherapy for many patients.

However, its impact on one type of disease, nonsmall cell lung cancer (NSCLC), is still not fully understood.

Our review aims to highlight the data for using proton therapy in NSCLC, with a focus on the clinical data—or lack thereof—supporting proton treatment for early and advanced stage disease.

New frontiers in proton therapy: applications in cancers

Cancer Communications 2019

Proton therapy offers dominant advantages over photon therapy due to the unique depth-dose characteristics of proton, which can cause a dramatic reduction in normal tissue doses both distal and proximal to the tumor target volume.

In turn, this feature may allow dose escalation to the tumor target volume while sparing the tumor-neighboring susceptible organs at risk, which has the potential to reduce treatment toxicity and improve local control rate, quality of life and survival.

Some dosimetric studies in various cancers have demonstrated the advantages over photon therapy in dose distributions.

Further, it has been observed that proton therapy confers to substantial clinical advantage over photon therapy in head and neck, breast, hepatocellular, and non-small cell lung cancers.

Comparative Effectiveness of Proton vs Photon Therapy as Part of Concurrent Chemoradiotherapy for Locally Advanced Cancer

JAMA, 2019

Concurrent chemoradiotherapy is the standard-of-care curative treatment for many cancers but is associated with substantial morbidity. Concurrent chemoradiotherapy administered with proton therapy might reduce toxicity and achieve comparable cancer control outcomes compared with conventional photon radiotherapy by reducing the radiation dose to normal tissues.

To assess whether proton therapy in the setting of concurrent chemoradiotherapy is associated with fewer 90-day unplanned hospitalizations (Common Terminology Criteria for Adverse Events, version 4 [CTCAEv4], grade ≥3) or other adverse events and similar disease-free and overall survival compared with concurrent photon therapy and chemoradiotherapy.

This retrospective, nonrandomized comparative effectiveness study included 1483 adult patients with nonmetastatic, locally advanced cancer treated with concurrent chemoradiotherapy with curative intent from January 1, 2011, through December 31, 2016, at a large academic health system. Three hundred ninety-one patients received proton therapy and 1092, photon therapy. Data were analyzed from October 15, 2018, through February 1, 2019.

In this analysis, proton chemoradiotherapy was associated with significantly reduced acute adverse events that caused unplanned hospitalizations, with similar disease-free and overall survival. Prospective trials are warranted to validate these results.