OUTBACK is an academic collaboration of the Australia New Zealand Gynaecological Oncology Group (ANZGOG), NHMRC Clinical Trials Centre at the University of Sydney, and NRG Oncology under the auspices of the international Gynecologic Cancer Intergroup (GCIG).

OUTBACK is a phase 3, randomised trial of adjuvant chemotherapy after chemoradiation as primary treatment for locally advanced cervical cancer compared to chemoradiation alone. OUTBACK included 926 women recruited from seven countries. The trial was sponsored by the University of Sydney and is registered on the Australian & New Zealand Clinical Trial Registry (ACTRN12610000732088).

Principal Investigator of the trial, Professor Linda Mileshkin, said,

“The OUTBACK results confirm that chemoradiation alone is currently our best standard treatment for women with locally advanced cervical cancer. The addition of adjuvant chemotherapy did not improve 5-year survival rates, but it did add significant side effects. Although some oncologists have been giving adjuvant chemotherapy outside of trials while awaiting the results of OUTBACK, this practice should now stop.”

Professor Mileshkin is Deputy Director of Medical Oncology at Peter MacCallum Cancer Centre.

“We need to find ways to improve the tolerability and completion of standard chemoradiation, as well as investigate other ways to improve survival rates for this group of women.”

Associate Professor Philip Beale, Chair of ANZGOG, said,

“OUTBACK has been a fantastic effort from investigators and trial units around the world. This global effort has culminated in a high-quality, rigorously conducted clinical trial, producing robust results that answer an important question for women with cervical cancer. Great credit is due to Principal Investigator Professor Linda Mileshkin for her pivotal role together with ANZGOG and our collaborators in generating these important results. Our heartfelt thanks go to the women, and their families, who participated in this trial, enabling us to move forward and test new ideas to improve the outcomes of women affected by cervical cancer”.

The trial results have been described as ‘immediately practice-changing’ by ASCO President Lori J. Pierce, MD, FASTRO, FASCO:

“This trial provides clear evidence that the addition of chemotherapy after chemoradiation does not extend survival. The results are immediately practice-changing, showing that this approach should not be used to treat locally advanced cervical cancer. We can now spare our patients the side effects and toxicity that comes with additional chemotherapy,”

ABOUT OUTBACK

OUTBACK is a phase 3 trial of adjuvant chemotherapy following chemoradiation as primary treatment for locally advanced cervical cancer compared with chemoradiation alone (ANZGOG 0902/ GOG 274).

OUTBACK originated from observations that while standard chemoradiation for women with cervical cancer was working well to cure many, 1 in 3 women were dying due to later developing distant metastatic disease. The trial aimed to show whether the addition of adjuvant chemotherapy after chemoradiation could improve survival.

OUTBACK is an international trial led by ANZGOG and the NHMRC Clinical Trials Centre at the University of Sydney. OUTBACK included 926 women from the USA (711), Australia and New Zealand (165), Canada (28), China, Singapore, and Saudi Arabia. The trial had financial support in Australia and New Zealand from the NHMRC Project Grant (APP1044349) and through the National Cancer Institute for the US sites. Hospira provided paclitaxel in Australia and New Zealand.

Key findings

The phase 3 OUTBACK trial showed that the addition of adjuvant chemotherapy following chemoradiation did not improve survival compared to standard chemoradiation alone in women with locally advanced cervical cancer.

At 5 years, overall survival was similar in the two treatment groups — 72% among those assigned adjuvant chemotherapy versus 71% among those assigned standard chemoradiation alone. Rates of progression-free survival at 5 years were also similar (63% versus 61%, respectively). Patterns of disease recurrence were also similar in the two treatment groups.

Severe side effects (grades 3-4) within a year of randomisation were experienced by more women assigned adjuvant chemotherapy than standard chemoradiation alone (81% versus 62%).

The trial also found that only 77% of women in each arm successfully completed all components of standard chemoradiation (including external beam radiotherapy, brachytherapy, and concurrent weekly chemotherapy with cisplatin).

Full results of OUTBACK will be presented in the Plenary Session at the American Society of Clinical Oncology (ASCO) Annual Meeting on Sunday 6 June, 1:00PM ET (Monday 7 June 2021, 3:00AM AEST).

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