Table 2 List of primary, secondary and additional variables and their assessment methods

Work outcomes

Working hours per week

Asking participants for their current number of actual working hours

1

n/a

Continuous

Change in working hours (%)

Asking participants for their current number of actual working hours and their contractual working hours at baseline.

1

n/a

Continuous (actual working hours at follow-up as a percentage of contractual working hours at baseline).

Employment status

Asking participants whether they are at work or not at work

1

n/a

Dichotomous

Time to return to work

Asking participants about their first day of returning to work, from which we will estimate the number of calendar days between the first day of sick leave and the first day of work, either fulltime or part-time, for at least 28 consecutive days without recurrence.

1

n/a

Continuous

Sick leave

Asking participants about the number of days they have been on sick leave in the past 6 months

1

n/a

Continuous

Readiness for return to work

The translated and adapted Dutch version [25] of the original RRTW questionnaire [15]. There are a number of items for each of the phases, with each item being scored on a 1 to 5 scale. Each RRTW stage will be scored by averaging all items within that stage. The stage with the highest summary score was considered the stage the participant was in. In case of a tie between stages, the lowest RRTW stage will be adopted. Based on this participants will be classified in any of the six RRTW phases.

21

6 stages

Ordinal

Work ability

Single question of the Work Ability Index (WAI) [27], asking participants to estimate their current work ability compared with their lifetime best on 0 to 10 scale (0 = cannot work at all; 10 = best ever);

1

10-point scale

Continuous

Health outcomes

Health-related work functioning

The validated [28] 27-item Work Role Functioning Questionnaire (WRFQ) [29], distinguishing five different work domains: work scheduling demands, mental demands, social demands, physical demands, and output demands (range 0 to 100). Higher scores indicate better work functioning.

27

0 to 100

Continuous

Health-related quality of life

For patients: the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire – Core 30 (EORTC QLQ C-30) [30]). This 30-item list consists of five multi-item functional scales (i.e., physical, role, emotional, cognitive, and social), three multi-item symptom scales (i.e., fatigue, pain, and nausea and vomiting), six single-item (i.e., dyspnoea, insomnia, appetite loss, constipation, diarrhoea, and financial impact), and a two-item global health and quality of life scale, all with a scoring range from 0 to 100. A higher score on the functional and global health and quality of life scales indicates better quality of life, while on the symptom scales, a higher score indicates a higher level of symptom burden. A summary score will be generated, calculated as the mean of all combined scale scores, excluding financial impact and the global health and quality of life scale.

30

0 to 100

Continuous

For partners: 12-item short-form health survey (SF-12) [31], expressed in t-score.

12

n/a

Continuous

Caregiver burden

The ‘Ervaren Druk door Informele Zorg-plus’ (EDIZ) [32], consisting of 15 items, ranging from 0 to 1, higher scores indicate a higher caregiver burden

15

0 to 15

Continuous

Depression

The Centre for Epidemiological Studies Depression Scale [33];, consisting of 20 items and a range of 0 to 60, a score of 16 and over indicates the possible presence of clinical depression

20

0 to 60

Dichotomous

Sociodemographic

Age

Asking participants about their age (in years)

1

n/a

Continuous

Gender

Asking participants about their gender (male/female)

1

n/a

Dichotomous

Marital status

Asking participants about their marital status with answer options: Not married, married without children, married with children, living together with partner, living together with partner and children, living together with others, single with children, divorced, widow/widower.

1

n/a

Categorical

Children

Number of children (living at home)

2

n/a

Continuous

Education

Asking participants about their highest education level completed with eight outcome options according to the Dutch education system.

1

n/a

Categorized in low, middle, high (according to International Standard Classification of Education (ISCED-97).

Income

Asking participants about their annual income (before tax) with answer options: <€30.000, €30.000–€60.000, €60.000–€100.000, and > €100.000.

1

n/a

Categorical

Breadwinner status

Asking participants about their breadwinner status with answer options: being sole breadwinner, not being breadwinner, being shared breadwinner with partner, don’t know

1

n/a

Categorical

Financial necessity of work

Asking about financial necessity of work

1

n/

Dichotomous

Medical

Cancer site*

Asking participants about their cancer site with 17 answer options (being the most common cancer sites) and the answer option ‘other’

1

n/a

Categorical

Time of diagnosis*

Asking participants for their time of diagnosis, which can be calculated in the time since diagnosis.

1

n/a

Continuous

Treatment(s)*

Received and future treatment(s). E.g. surgery, radiation, chemotherapy, hormonal therapy, or combination, and medication

1

n/a

Categorical

Cancer recurrence(s)*

Asking about recurrence of cancer in the follow-up questionnaires.

1

n/a

Dichotomous

Lifestyle

Smoking

Asking participants about their smoking status with answer options: smoker, ex-smoker, non-smoker.

1

n/a

Categorical

Alcohol consumption

Asking participants about their alcohol consumption with answer options: Never, only at festive occasions, several times a month, once a week, several times a week, daily.

1

n/a

Categorical

Physical activity

Asking participants about how many days a week they spend at least 30 min cycling, household activities, gardening or sports.

1

0 to 7

Continuous

Health

Comorbidities

14-item comorbidity questionnaire [34]. For partners this also includes a question about cancer.

14

0, 1–2 or ≥ 3 comorbidities

Categorical

Fatigue

For cancer survivors: Functional Assessment of Chronic Illness – Fatigue scale (FACIT-F [35];). This 13-item questionnaire has a scoring range from 0 to 52. A higher score on this scale means less fatigue.

13

0 to 52

Continuous

For partners: The ‘Checklist Individuele Spankracht’ (Checklist Individual Strength) that has been described in Dutch [36] and has been used on samples of workers before [37]. The scale consists of 20 items with outcome categories on a 1 to 7 scale. Summary scores (potentially using four subscales) range from 20 to 140, with higher scores indicating more fatigue.

20

20 to 140

Continuous

Employment

Main tasks

Asking participants whether they engage in a job with mainly mental, mainly physical or a combination of mental and physical tasks

1

n/a

Categorical

Years in current position

Asking participants about how many years they have spent in the current job position regardless of current employer.

1

n/a

Continuous

Years of paid employment

Asking participants about how many years they have spent working in general and at their current employer

1

n/a

Continuous

Contract type

Asking participants about their contract type with four answer options: permanent contract, contract for fixed amount of time, secondment contract, contract through employment agency.

1

n/a

Categorical

Shift work

Asking participants what sort of shifts they work in with answer options: day shifts, and shift work.

1

n/a

Dichotomous

Company size

Asking about the size of the company with answer options 1–9, 10–99 and ≥ 100

1

n/a

Categorical

Company sector

Asking participants about their company sector, with 13 answer options (depicting the most common occupational sectors in the Netherlands) and the answer option ‘other’

1

n/a

Categorical

Time since first day of sick leave

Asking participants about their day of sick listing, from which the number of days between the first day of sick leave and enrolment in the study can be calculated

1

1

Continuous

Employment status partner (if applicable)

Asking participants whether their partner has a job (full-time or part-time), with answer option yes/no

1

n/a

Dichotomous

Caregiving leave

Asking participants whether they take caregiver leave (yes/no), and if so, for how many hours per week.

2

n/a

Dichotomous and continuous

Work

Social support from supervisor/colleagues

Two subscales of the validated Dutch version of the Job Content Questionnaire (JCQ [38];), with four items each (range 4–16).

8

4 to 16 (per subscale)

Continuous

Job insecurity

One item (four point scale) of the Dutch Questionnaire on Perception and Judgment of Work (VBBA [39];).

1

4-point scale

Continuous

Need for recovery

11-items (two point scale) of the VBBA [39].

11

0 to 22

Continuous

Work accommodation

Structural changes in the job/function, and the contracted working hours, but also regarding offered and accepted accommodations, e.g., lighter work, reduced hours, modified tasks, more breaks, flexible schedule.

9

n/a

Categorical

Impact of COVID-19 on work

Five self-established questions asking participants about the impact of COVID on their work.

5

n/a

Categorical

Work attitude

Dutch version of the Work Involvement Scale [40]. The scale consists of six statements regarding work and working in general, that are all scored on a 7-point scale. A sample item is: ‘Having a job is very important to me.’

6

0–36

Continuous

Self-efficacy

The Dutch version of the 12-item General Self-Efficacy scale [41] (range 12–60). A sample item is: ‘When I have decided to do something, I will definitely do it.’ The Dutch version consists of 10 items.

10

11–60

Continuous

Work-family balance

Five questions (four point scale) from the Copenhagen Psychosocial Questionnaire (COPSOQ II [42];). A higher score indicates more work-family imbalance.

5

4-point scale

Continuous

Work intention

One question: ‘In your estimation, what are the chances that you will be at work in 6 months?’, measured with a 10-point rating scale from 1 (no chance) to 10 (very high chance).

1

10-point scale

Continuous

Fear of COVID-19

A Dutch translation (provided by our research group) of the fear of coronavirus-19 scale [43]. The scale consists of 7 items and is scored on a 5-point rating scale, ranging from 1 (strongly disagree) to 5 (strongly agree). A higher score indicates higher fear of COVID-19.

7

7–35

Continuous

Expectations regarding return to work

Two questions indexing whether they have a return date in mind (yes/no), and if so, what that date is.

2

n/a

Dichotomous / continuous

Economic evaluation

Health care consumption

Asking which health care professionals were visited and which medication was taken, using the iMCQ questionnaire.

19

n/a

Continuous

Productivity loss

Asking about productivity loss, using the iPCQ questionnaire.

Varying

n/a

Continuous

Quality of life/utility

Asking about the quality of life, using the EQ-5D questionnaire (EuroQol-5D-5L [44])

Varying

n/a

Continuous