SOLD is a randomised phase III study comparing the efficacy of adjuvant chemotherapy given concomitantly with trastuzumab (Herceptin®) for 9 weeks, with the current standard of care consisting of 9-week adjuvant chemotherapy plus single-agent trastuzumab administered for 12 months in patients with early-stage HER2-positive breast cancer.

The trial hypothesis is that anti-HER2 treatment (trastuzumab) given for 9 weeks concomitantly with adjuvant chemotherapy is not inferior in efficacy compared with the same regimen plus single-agent trastuzumab administered for 1 year, which is the current standard.

Short treatments have several potential advantages. They may be less cardiotoxic, they may require no cardiac monitoring, they require fewer hospital visits, and they are less costly.

Administration of potentially synergistic agents with trastuzumab might be more important than extending administration of trastuzumab. This is where the name of the SOLD trial comes from.

The primary results, which were presented at SABCS 2017, support the current practice with 90.5% disease-free survival in the 12-month trastuzumab arm and 88% in the 9-week arm. However, no substantial difference was found in distant disease-free survival and overall survival between the two arms.

These findings indicate that administration of potential synergistic agents in combination with brief anti-HER2 treatment is not superior in efficacy compared with extended administration of trastuzumab, as the trial hypothesis had suggested.

However, based on subgroup analyses, the study investigators also reported discrepancies in survival outcomes influenced by the dose of docetaxel when given concomitantly with trastuzumab.

Further research is necessary to understand this important interaction as well as investigate dual HER2-inhibition for this group of breast cancer patients.

Synergistic drug combinations could lead to shorter treatments which have several advantages for patients and society, i.e. fewer toxicities and costs.

Upon registration in the study, patients were randomly allocated to one of the two following arms:
 – trastuzumab (9 weeks) + docetaxel +CEF
 – trastuzumab (9 weeks) + docetaxel + CEF + trastuzumab (up to 51 weeks)

Participants will be followed up for a minimum of 8 years post-randomisation or until death.

Women of 18 years old or older, diagnosed with early HER2 positive breast cancer with a high risk of disease recurrence.

In total 2,176 patients were recruited (patients accrual was officially closed in December 2016).

This study is coordinated and sponsored by the Finnish Breast Cancer Group (FBCG), and it is conducted under the umbrella of the Breast International Group (BIG).

The total number of patients enrolled in the study was reached in December 2014.
Data are currently being analysed, with the expectation to present the study results at a medical conference and to the public in the near future.

A total of 63 centres from 7 countries (Belgium, Finland, Iceland, New Zealand, Serbia, Sweden, UK) participated in SOLD.

Joensuu H, Fraser J, Wildiers H et al. Effect of Adjuvant Trastuzumab for a Duration of 9 Weeks vs 1 Year With Concomitant Chemotherapy for Early Human Epidermal Growth Factor Receptor 2-Positive Breast Cancer: The SOLD Randomized Clinical Trial. JAMA Oncol. 2018 May 31. doi: 10.1001/jamaoncol.2018.1380