The aim is, in a randomized controlled trial, to test the feasibility and evaluate the efficacy of an internet-based treatment for insomnia, previously tested in a group of 28 US cancer patients, in a large sample of Danish breast cancer survivors who are experiencing significant sleep problems 0-3 years after treatment. The investigators aim to test the following hypotheses: That a group receiving Internet-delivered cognitive-behavioral therapy (CCBT) for insomnia (CCBT-I) will experience reduced sleep latency, more hours of sleep, fewer awakenings during the night, improved sleep efficiency, increased subjective sleep quality, and improved quality of life after the intervention, when compared to a waiting list control group. The investigators also aim to explore a number of possible moderators of the effect (comorbidity, depression, fear of cancer recurrence tendency to ruminate) and mediating mechanisms (changes in sleep habits and sleep-related lifestyle factors).

METHODS PARTICIPANTS

The participants are able, legally competent women, 18 years or older, from a national cohort of Danish women treated for primary breast cancer between 1st of June 2011 and 1st of Juli 2014:

Inclusion criteria: 1) Reported moderate-to-severe sleep disturbances, defined as a score> 5 on the Pittsburgh Sleep Quality Index (PSQI) (32;33) (see below), and 2) are found to be disease free. Furthermore, participants 3) are required to have access to the Internet.

Exclusion criteria: 1) Recurrence of breast cancer, 2) a second cancer, 3) and other serious physical or psychological comorbidity (e.g. depression, cardiovascular disease, and COPD), 4) shift work schedule, 5) other sleep disorders (sleep apnea, narcolepsy).

PROCEDURE INFORMATION AND REQUEST TO PARTICIPATE Women who fulfill the inclusion criteria and indicate an interest in receiving further information receive an information folder by post informing.

BASELINE MEASURES:

The baseline questionnaires contains questions about sleep quality, fatigue, depression, anxiety, quality of life, sleep habits and sleep-relevant lifestyles, together with use of health care services, sleep medication, and use of alternative medicine with the aim of treating sleep problems.

INTERVENTION:

The intervention program is designed to be completed in 6 weeks. To ensure that all participants have opportunity to complete the program they are granted access to the program for nine weeks .

POST-INTERVENTION:

After the intervention, participants in both groups are asked to complete a post-intervention questionnaire package and then to fill in the sleep diary for a 2-week period.

FOLLOW-UP:

After an additional 4 weeks both groups complete two sleep questionnaires (PSQI and the insomnia severity index) after which the waiting list group is offered the intervention.

INTERVENTION The Internet intervention offered is the SHUT-i program (Sleep Healthy Using The Internet), which is based on the existing consensus concerning non-pharmacological treatment of insomnia and builds on previous validated CBT's for insomnia (CBT -I) (34).

CONTROL GROUP Participants randomly assigned to the control condition are told that for practical reasons, they have to wait 15 weeks before partaking in the intervention.

PRIMARY ENDPOINTS A) Sleep diary (bedtime, sleep onset latency (SOL), number of awakenings, total length of awakenings, wake time, arising time, daytime naps, rating of soundness of previous night's sleep, rating of refreshed feeling upon morning awakening, and information about sleep aids : medication and/or alcohol use).

B) The Pittsburgh Sleep Quality Index (PSQI) (33). C) The Insomnia Severity Index (ISI) (39).

NUMBER OF PARTICIPANTS The combined effects found in the meta-analysis of published randomized trials of Internet-based treatment for insomnia (30) are: sleep quality (d=0.41), sleep efficiency (d=0.40), number of awakenings (d=-0.45), sleep onset latency (d=-0.55), total minutes slept (d=.22), time spent in bed (d=.25). If the investigators aim to detect an effect corresponding to an average of the effects above (d = 0.38) with 80% statistical power, at least 2 x 109 participants are required.

ETHICAL CONSIDERATIONS The investigators will adhere to the general ethical guidelines for human trials. All participants receive oral and written information about the project. They are informed that they can withdraw at any time from the study with no consequence for their current or future treatment. Participants are advised to continue any medical treatment for insomnia, and to consult a doctor before changing medical regimen.

PRIVACY AND DATA SECURITY The SHUT-I program stores any personal information in a separate one-way system that cannot be accessed from the Internet but only locally by the SHUT-i administrators. Connections between personal information and other data are encrypted. Data is stored physically on servers in locked facilities, in the United States.

ADVERSE EFFECTS, INCONVENIENCES, BENEFITS, AND RISKS The investigators do not expect Internet-based cognitive behavioral therapy to be associated with any adverse health effects or risks as no adverse effects has been reported for conventional CBT for insomnia.

Inclusion Criteria:

• Reported moderate-to-severe sleep disturbances, defined as a score> 5 on the Pittsburgh Sleep Quality Index (PSQI).
• Disease free.
• Access to the Internet.

Exclusion Criteria:

• Recurrence of breast cancer
• A second cancer
• Other serious physical or psychological comorbidity (e.g. depression, cardiovascular disease, and COPD)
• Night work schedule
• Other sleep disorders (sleep apnea, narcolepsy) .