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For prostate cancer patients with aggressive, Gleason 9-10 disease, treatment with radiotherapy plus hormone therapy was at least as effective as surgical strategies in a retrospective study.

In terms of prostate cancer–specific mortality, outcomes were similar between the 50 patients treated with an aggressive surgical approach, so-called MaxRP, compared with 80 patients on aggressive radiotherapy or MaxRT (adjusted HR 1.33, 95% CI 0.49-3.64, P=0.58), reported Anthony V. D'Amico, MD, PhD, of Dana-Farber Cancer Institute in Boston, and colleagues.

And all-cause mortality was also similar between the two groups (adjusted HR 0.80, 95% CI 0.36-1.81, P=0.60), they wrote in .

MaxRP consisted of radical prostatectomy plus adjuvant external beam radiotherapy (EBRT), and androgen deprivation therapy (ADT), while MaxRT included EBRT plus brachytherapy and ADT.

"Just because there's no difference in the risk does not necessarily mean they're equivalent," cautioned D'Amico in an that accompanied the study, noting the wide confidence interval for prostate cancer–specific mortality.

To that end, the researchers used plausibility indexes to examine the two treatment methods and found 76.75% and 77.97% likelihoods of equivalence for the prostate cancer–specific mortality and all-cause mortality endpoints, respectively.

"This does not substitute for a randomized trial, and unfortunately we don't have one that's going to look just at the Gleason 9-10 subset, and the ones that are completed did not stratify by Gleason 9-10," said D'Amico. "Therefore, this data that we have presented in this study stands as the only data really that will exist now and will exist in the future ... on this very important subset, which makes up most of prostate cancer death."

The researchers also found that patients treated with surgery alone or with ADT appeared to have worse prostate cancer–specific mortality compared with the MaxRT group:

• Surgery alone (adjusted HR 2.80, 95% CI 1.26-6.22, P=0.01)
• Surgery plus adjuvant ADT (adjusted HR 3.15, 95% CI 1.32-7.55, P=0.01)

And all-cause mortality:

• Surgery alone (adjusted HR 1.65, 95% CI 0.94-2.91, P=0.08)
• Surgery plus adjuvant ADT (adjusted HR 2.33, 95% CI 1.23-4.42, P=0.01)

The findings build upon an earlier retrospective study from Amar Kishan, MD, of the University of California Los Angeles, and colleagues that found EBRT plus brachytherapy was associated with significantly lower prostate cancer–specific mortality than either EBRT alone or radical prostatectomy.

Commenting on the current study, Kishan told 番茄社区app that these data confirm the findings from his group, and highlighted the new data on MaxRP/MaxRT equivalence.

"We did not find this to be the case in our study, so this is a novel finding," he said. "It underscores the importance of multimodality therapy in this disease."

Kishan also noted that in this study the MaxRT benefit persisted despite a shorter median hormone therapy duration (6 months, with 75% of patients receiving ADT for less than a year). He explained that standard of care for ADT in this setting would be 12 months at the minimum, and that, in his previous study, median ADT duration was 12 months.

"On the one hand, the new study suggests that a shorter than standard duration of ADT may be sufficient to capture a benefit above radical prostatectomy," he said. "However, it is unclear whether a more standard duration of 12 months would lead to outperformance of radical prostatectomy plus EBRT with or without ADT."

The retrospective study from D'Amico and colleagues examined outcomes in 639 men with clinical T1-4 Gleason score 9-10 non-metastatic prostate cancer without nodal involvement. From 1992 to 2013, there were 80 men treated with MaxRT and 559 men treated with radical prostatectomy and pelvic lymph node dissection at a tertiary cancer center.

There were 372 men (66.5%) treated with radical prostatectomy alone, while 88 patients (15.7%) also had adjuvant EBRT, 49 patients (8.8%) also had ADT, and 50 patients (8.9%) had the MaxRP treatment with both EBRT and ADT. Median follow-up was 5.51 years in the MaxRP arm compared with 4.78 in the MaxRT arm.

With regard to patient characteristics, D'Amico noted that the two arms were very similar. "Not everybody, but in the 80%-plus range of people, had adverse pathologic findings," he noted. "As a result you are getting much closer to apples versus apples."

Due to their high Gleason scores, all patients in the current study would be considered unfavorable from the start, eliminating a situation where favorable patients are perhaps more likely selected for surgery. "That issue of apples versus oranges is much less so in a study of Gleason 9-10 than it would be in a Gleason 7 study," he said.

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