There is now robust evidence, based on numerous randomized clinical trials, that moderate hypofractionation offers patients similar outcomes as conventional radiotherapy dose-fractionation schedules. That appears to be the case “across the spectrum of localized prostate cancer (low-, intermediate-, [and] high-risk disease),” Dr Chen said.

“Thus, moderate hypofractionation is considered [the] standard of care for almost all patients with localized prostate cancer,” he said.

For ultrahypofractionation (completing radiotherapy in 1 to 2 weeks), the evidence base is largely limited to patients with low- or intermediate-risk malignancies.

“Data on high-risk cancer are emerging, and I believe this ultrahypofractionation will likely become more commonly used for high-risk cancer in the future,” Dr Chen said.

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However, the optimal approach to delivering SBRT is unclear – and is likely to remain unclear.

“Unfortunately, a randomized trial will likely never be conducted to compare different technologies for SBRT,” Dr Chen said. “The Cyberknife® technology is unique in that it tracks the prostate in real-time during each treatment session; whether this helps improve cure rates or reduce side effects compared to other machines is unknown.”

Ultrahypofractionation is more convenient for patients but adoption has been slower than anticipated, Dr Chen noted.

SBRT equipment is expensive and ultrahypofractionated SBRT yields lower reimbursements to cancer centers than longer moderate- and conventional-fractionation radiotherapy dosing schedules. Until now, concern about acute toxicity profiles might also have tempered enthusiasm for ultrahypofractionation.

There have been barriers to its adoption, Dr Chen acknowledged. “Centers need to have appropriate stereotactic radiotherapy equipment and expertise in order to adopt this treatment to benefit their patients,” he explained.

Wider adoption will come, however, according to Dr Chen. “It is hard for me to imagine shortening treatment any further than this,” he said. “This treatment, short in duration and with little recovery afterwards, is an appealing option for patients.”

More data are still needed on SBRT ultrahypofractionated radiotherapy’s efficacy against high-risk prostate cancer, Dr Chen concluded — as well as more information about whether adding androgen deprivation therapy to SBRT provides any benefit to cancer control or survival, he said.

Update: This article was updated on 11/7/19 to clarify how ultrahypofractionated radiotherapy can potentially cut total treatment course times.

References

  1. Widmark A, Gunnlaughsson A, Beckman L, et al. Ultra-hypofractionated versus conventionally fractionated radiotherapy for prostate cancer: 5-year outcomes of the HYPO-RT-PC randomised, non-inferiority, phase 3 trial. Lancet. 2019;394(10196):385-395.
  2. Brand DH, Tree AC, Ostler P, et al. Intensity-modulated fractionated radiotherapy versus stereotactic body radiotherapy for prostate cancer (PACE-B): acute toxicity findings from an international, randomised, open-label, phase 3, non-inferiority trial. Lancet Oncol. 2019;20(11):P1531-1543.