This multicenter study is a sequential RCT which aims to prove, in the first stage, the efficacy of a face-to-face Positive Psychotherapy in Cancer (PPC) group compared to a Cognitive Behavioral Stress Management (CBSM) group. In the second stage, the common face-to-face version of the PPC will be compared with its online version via videoconference (Online group Positive Psychotherapy, OPPC) among a group of primary breast cancer survivors. The principal dependent variables assessed will be emotional distress, post-traumatic growth (PTG) and quality of life (QoL). Some treatment predictors of psychosocial response will be explored. Lastly, an economic analysis focused on the Quality Adjusted Life Years (QALY) will be carried out at each stage. For the first stage, we hypothesize that the PCC group would achieve similar efficacy in reducing participants' distress compared to the CBSM group, while the PCC group would show greater improvement in PTG than the CBSM group. For the second stage, it is hypothesized that the OPCC would achieve similar efficacy in all psychosocial variables and guarantee equivalent retention and adherence compared to face-to-face PPC.

Psychosocial treatments in cancer survivors have demonstrated their efficacy in reducing emotional distress and improving Quality of Life (QoL). Providing access to a psychosocial intervention at the end of a curative cancer treatment becomes worthwhile, not only because it reduces the use of other medical resources and promotes return-to-work, but also because it facilitates oncological treatment adherence and the adoption of healthy lifestyles. Online psychosocial treatments are a good option because of their easy access, anonymity and low cost. The study is a sequential multicenter, controlled and randomized clinical trial organized in two stages. It is worth highlighting that there was a deviance from the initial research plan which contemplated a three-arm clinical trial. However, during the preparation of the recruitment phase, we faced some problems related to the opening of the third arm (online group positive psychotherapy) due to the fact that the required technology that supported the online group psychotherapy was not available for use at that moment. As a result, we decided to wait for a few months before we activate the third arm of the study. In conclusion, the study aims to prove, in the first stage, the efficacy of a face-to-face Positive Psychotherapy in Cancer (PPC) group compared to a Cognitive Behavioral Stress Management (CBSM) group. In the second stage, the common face-to-face version of the PPC will be compared with its online version via videoconference (Online group Positive Psychotherapy, OPPC). Those breast cancer survivors who have showed moderate or severe adaptation problems after the completion of their oncological treatment will be randomly assigned to PPC versus CBSM group for the first stage of the study (January 2013-December 2015), and for the second stage, a different group of breast cancer survivors will be assigned to PPC versus OPCC (January 2016-February 2019). Regarding the methodology of the study, participants from the 4 groups will be evaluated using a battery of measures at the beginning of the study (T0), post-treatment (T1), 3 months from T1 (T2) and 12 months from T2 (T3). Therefore, this study will use a factorial design of 3 (treatment conditions) x 4 (evaluation points).The main outcome measures include: quality of life, anxiety, depression, post-traumatic stress and post-traumatic growth. Secondary outcome measures will be: healthy lifestyles, adherence to the oncological treatment, perceived social support, and the number of return-to-work days after the cancer treatment completion.

Data will be analyzed using SPSS 21.0 version. For the first stage, we hypothesize that the PCC group would achieve similar efficacy in reducing participants' distress compared to the CBSM group, while the PCC group would show greater improvement in PTG. For the second stage, it is hypothesized that the OPCC would achieve similar efficacy in all psychosocial variables and guarantee equivalent retention and adherence compared to face-to-face PPC. Besides, the presential format will be more effective for severely distressed patients with previous history of trauma, while the online format will be more effective for younger patients with mild emotional distress.

Inclusion Criteria:

• Diagnosed with primary breast cancer,
• Having completed the curative treatment and / or adjuvant treatment for their primary tumor in the last 1 to 6 months
• Be able to use the Internet in a private place and have a knowledge of Internet at the user level
• Scoring ≥ 5 points on the thermometer for emotional distress (anxiety and depression) and confirmed with a score on the HADS total scale ≥ 10 in the admission interview.

Exclusion Criteria:

• Severe major depressive episode or significant autolytic ideation
• Showing symptoms of psychosis or substance abuse.
• If a participant relapses or progresses from her illness during the study period, the clinical psychologist responsible for the therapeutic group to which is assigned will ask the participant if they want to be referred to their hospital for individual psychological treatment.