The goal of this observational study is to investigate whether daily physical activities measured with a smartphone are related to the possible side effects or other physical complaints that arise as a result of cancer treatment. The investigators want to test whether the number of steps per day, both before and during treatment, are related to possible side effects or other physical complaints of the treatment using a smartphone. Knowledge about this relationship gives us possible starting points to prevent and/or reduce side effects and improve treatment outcomes. Additional research would then be needed.

The investigators also want to investigate whether these daily measurements are feasible for patients undergoing treatment.

Participation in the study involves measuring daily physical activity from the week before treatment until the first 3 months of treatment have been completed. This is done by tracking daily steps with patients own phone using the OncoSTAPP application.

Rationale: Systemic treatment of patients with cancer has a multimodal approach with the goal of balancing quantity and quality of life. Treatment decisions are influenced by tumour and patient-related characteristics. Additionally, in clinical practice performance status is used to identify whether a patient is sufficiently fit for systemic treatment, as it has shown to be a valid prognostic factor for survival and adverse events during treatment. However, treatment-related toxicities and hospitalisations occur frequently during systemic treatment.

The disadvantages of performance status assessed with ECOG or Karnofsky, is that it is a subjective measurement which is prone to bias and has high interobserver variability. Also a patient's self-reported physical function is significantly associated with shorter (progression-free) survival, but it is also subjective and is prone to multiple forms of bias. Objective assessment of physical function might be a good alternative to counteract these shortcomings. A higher level of physical activity is associated with a reduction in cancer specific mortality and can be measured with accelerometers, pedometers or multisenor systems like smartphones.

Wearable measured step count assessed with a wrist worn device provided by the investigators has shown to be associated with adverse events. However, these devices cannot be provided to all patients in clinical practice.

Recently, the investigators showed that the smartphones' assessments of physical activity (step count), have excellent agreement with accelerometer assessments of physical activity and good test-retest reliability. Furthermore this smartphone measurements were associated with early trial discontinuation in phase 1/2 cancer trials.

The investigators hypothesize that a low baseline and/or a reduction in physical activity (step count) measured with smartphones will be predictive for clinically relevant adverse events during systemic treatment. Adding objective information of physical function in the process of selecting the best treatment for a patient may help prevent unnecessary adverse events. Additionally, a detection of a decline in physical activity during treatment may identify upcoming adverse events early, allowing timely management/support. This may help to optimize treatment and quality of life.

Objective: Primary objectives: 1) To determine whether baseline physical activity, measured by the number of steps per day with a smartphone, is associated with clinically relevant adverse events during treatment.

2) To determine whether changes in physical activity, measured by the number of steps per day with a smartphone, are associated with clinically relevant adverse events during treatment.

Clinically relevant adverse events during treatment are defined as hospitalizations, early treatment discontinuation, relative dose intensity below 70% and mortality.

Secondary: Patients' acceptability of the application. The association of physical activity with relative dose intensity, progression free and overall survival. The association between the oncologists' estimates and clinically relevant adverse events during treatment, and the possible added value of objective assessments of physical activity.

Study design: Prospective observational cohort study.

Study population: 411 patients with cancer referred for systemic treatment at the departments of Medical Oncology at participating centres.

Intervention: N/A.

Main study parameters/endpoints: Collection of daily number of steps will start in the week before treatment and will continue for the first 3 months of systemic treatment. Mean number of steps per day will be measured passively with a smartphone application on patients' own smartphones. Primary endpoint is any clinically relevant adverse events during treatment, defined as hospitalizations, significant dose modifications of treatment and mortality.

Nature and extent of the burden and risks associated with participation, benefit and group relatedness: Participation in this study will not cause any additional risks or expected benefits for participants. No extra visits to the hospital will be necessary. It will provide us knowledge, which may be used in the future to better select patients for systemic treatment.

Patients will be asked to carry their smartphone on them during the duration of the study.

Inclusion Criteria:

• Age ≥18 years;
• Diagnosis of cancer with an indication of starting systemic treatment
• Knowledge how to handle smartphone with iOS version 11 or higher or Android version 7.0 or higher.
• Mastery of Dutch language
• Able and willing to give written informed consent

Exclusion Criteria:

• Cognitive disorders or severe emotional instability
• Wheelchair-depended at home, or immobile due to for example fracture
• Already participating in an exercise trial

All patients with cancer referred for systemic treatment of the outpatient clinic at the departments of Medical Oncology at participating centres.

No current plans for data sharing. Patients gave informed consent to share data with studies in line with the current research question. Data availible on request.

Till 15 years from start data collection

Research question in line with current