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Expert Takeaways from the ASTRO Annual Meeting

Roach, Michael C. MD; Robinson, Cliff G. MD

doi: 10.1097/01.COT.0000476186.15457.c3
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SAN ANTONIO—This year's Annual Meeting of the American Society for Radiation Oncology brought together more than 11,000 radiation oncologists, radiation therapists, medical physicists, dosimetrists, oncology nurses, and cancer center administrators. Nearly 3,000 abstracts were submitted for presentation at this meeting which is the largest of its kind serving the international radiation oncology community. The theme this year was “Technology Meets Patient Care.”

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IMRT

The benefits of the advanced technology behind intensity-modulated radiation therapy (IMRT) were highlighted in several clinical trials. Despite the fact that IMRT was used to treat larger and less favorable non-small cell lung tumors in the Phase III RTOG 0617 trial, IMRT was associated with a reduced rate of severe pneumonitis and an improved likelihood of patients being able to receive full doses of consolidative chemotherapy.

Use of IMRT was also able to reduce the doses to the heart that had been previously been shown to be highly prognostic for survival.

Similarly in cervical cancer, interim results of an Indian Phase III study of postoperative IMRT versus conventional 3D-conformal radiation suggested a reduction in the rates of grade 3 or greater bowel toxicity at two years. Disease-specific outcomes are still pending.

Combining the technology of brachytherapy and external-beam therapy proved beneficial in the Canadian Phase III trial ASCENDE-RT. In this trial, patients with intermediate- and high-risk prostate cancer were treated with a year of androgen deprivation, and received radiation to the whole pelvis eight months after the initiation of androgen deprivation.

The randomized use of a low-dose rate iodine-125 seed implant as a focused boost to the prostate cut the incidence of a PSA relapse in half compared with the use of an external-beam boost to the prostate at 6.5 years. This came at the cost however, of worse bodily pain, general health, sexual function, and urinary function quality of life.

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Combined RT + Checkpoint Inhibitors

Combining the latest in radiation therapy with immune checkpoint inhibitors was also highlighted. A single-institution Phase I trial was able to safely unite the use of a CTLA4 antibody for metastatic melanoma with escalating doses of radiation in three fractions to a single index lesion. Major tumor regressions were observed in patients. In parallel mouse studies, even with dual checkpoint blockade with anti-PD-L1 and anti-CTLA4 inhibitors, omission of radiation resulted in higher rates of relapse.

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Therapy De-escalation

However, therapy de-escalation was also emphasized. Results from a prospective Phase III trial in China showed that in esophageal cancer, treatment volumes could be reduced to only lymph nodes involved at diagnosis rather than the conventional treatment of elective nodal regions. This reduced toxicity without compromising loco-regional recurrence, distant metastasis, and overall survival.

The Phase III Dutch HYPRO trial in intermediate- and high-risk prostate cancer patients attempted to cut the number of radiation treatments in half, from 39 fractions of 2 Gy to 19 fractions of 3.4 Gy.

Two thirds of patients received androgen deprivation. With a median follow-up of five years, relapse-free survival and overall survival did not differ. There was no difference in late urinary or gastrointestinal toxicity, though there was worse acute gastrointestinal toxicity with the shorter regimen. Lower Gleason scores and greater than one year of androgen deprivation were associated with better disease outcomes.

Similarly in low-risk prostate cancer, the results of RTOG 0415 showed no difference at five years in disease-free survival and biochemical PSA recurrence between 41 fractions of 1.8 Gy over 8.2 weeks versus 28 fractions of 2.5 Gy over 5.6 weeks. Physician-reported late but not acute grade 2 toxicity was slightly worse with the shorter regimen, however.

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ESTRO Study of APBI

ESTRO, the European counterpart to ASTRO, showed that one week of accelerated partial breast irradiation using interstitial multicatheter brachytherapy resulted in no difference in the approximately one percent local recurrence rate when compared with six weeks of conventional whole-breast external-beam radiation with a boost.

Nodal, distant, and contralateral breast recurrences were also not significant and each risk of similar magnitude. The trial enrolled over 1,000 women over 40 years of age with less than 3 cm of ductal carcinoma in-situ or invasive breast carcinoma with clear 2 mm resection margins and no more than microscopic nodal metastases.

These encouraging results of this technically difficult partial-breast method beat those shown in randomized trials of intra-operative partial-breast radiation. Long-term outcomes and cosmetic outcomes were not reported.

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Magnetic Resonance Image-Guided Therapy

The emerging use of magnetic resonance image-guided therapy received special attention at this meeting. The ability to track the motion of the pharyngeal airway and tumors of the liver was highlighted. The technique's novel ability to adapt therapy with each fraction of stereotactic treatment of thoracic and abdominal primary malignancies and oligometastases was also demonstrated.

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Lower-Tech Interventions

Lower-technology interventions were also presented, with analyses showing improved outcomes when hyperglycemia is controlled in patients with advanced cervical cancer and when patients quit smoking after stereotactic radiation treatment of early lung cancers.

NCIC CTG SC.23 showed that compared with placebo, the simple intervention of 8 mg of dexamethasone given once daily for five days significantly reduced the rate of radiation-induced pain flares from 30 to 20 percent. Radiation was given in a single fraction of 8 Gy to one to two metastases from a solid tumor. This reduction in the pain flare occurred in the first five days after treatment.

After 10 days, patients showed significant improvements in nausea, appetite, and patient function. No difference in response to radiation, toxicity, and death was observed. No hyperglycemia requiring hospitalization occurred.

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‘We Are Doctors First’

The meeting's presidential address, entitled “We are doctors first,” was delivered by Bruce Minsky, MD, FASTRO. “Remarkable advances in technology have led to advances in the design, delivery, and overall results of radiation therapy for the treatment of cancer,” he said. At the same time, he emphasized that the responsibility to be a skilled and compassionate physician is equally important: “Technology and outstanding patient care are complementary, not competitive with technology.”

Copyright © 2015 Wolters Kluwer Health, Inc. All rights reserved.
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