Since quality of life has gained increasing importance in clinical oncology over the last 15 years, current quality of life inventories now focus on physical, mental, cognitive, social and other dimensions along with chemotherapeutical effects. These comprise the EORTC QLQ C30 1 of the European Organisation for Research on Treatment of Cancer, including additional scales for specific types of tumours 2 or the Functional Assessment of Cancer Therapy – FACT 3 which, next to the basic module, also contains symptom-specific supplementary modules 4. Generic questionnaires such as the Medical Outcome Study SF-36, which is also used for oncologic patients, capture the rehabilitative, physical, emotional and social functional status 5.

New studies have yielded some evidence that questionnaires capturing the individual skills of adaptation such as the 'sense of coherence' 6 or 'self-regulation' (Grossarth-Maticek 1999) could be more appropriate as prognostic tools in oncology or in other chronic conditions than conventional health-related quality of life (HRQL) scales 7. However, inventories which capture the 'Sense of Coherence' (SOC) based on Antonovsky's concept of salutogenesis have mainly been validated in psychosomatic and psychiatric patients 68. Antonovsky's initial question was: What keeps a person healthy? For Antonovsky, health is a continuum between total disease (dis-ease) and complete health (ease). Salutogenesis is a concept based around stress and resilience. The question of salutogenesis contrasts with a central question of scientific medicine into pathogenesis: What makes a person ill? 6. The SOC is based on three components which are considered prerequisites for salutogenesis: comprehensibility, meaningfulness and manageability.

1) According to Antonovsky, these three factors determine to what extent a person can rely an existing, enduring but also dynamic feeling of trust, which gives structure to the course of internal as well as external events and makes them understandable.

2) These resources have to be available when required and

3) the situation must be understood as challenges which deserve rising to 9.

New epidemiological studies have articulated the potential prognostic relevance of SOC for cancer patients 7. However, Antonovsky was a sociologist and did not extend his work to people with chronic illness, focusing instead on survivors of the Holocaust. Thus, although the current SOC scale includes general questions about life style, attitudes to life, and mental health 10 which are relevant to all groups of people, it does not address physical health. But rather than containing references to physiological parameters as postulated by Antonovsky 89, due to its origin, it focuses in particular on mental health. Already, in 1923 a first medical approach to salutogenesis was discussed 11. All in all, it therefore there is a need to develop a questionnaire with a stronger focus on patients with chronic diseases, particularly cancer.

Here we report a two stage validity study which aimed to validate the ICS which was developed based on a non-standardised open questioning process of cancer patients before starting the study and expert ratings from questions on disease management, outlook on life and drive, perception of health and thermoregulation for oncological patients. We followed development of the instrument by testing reliability, and validity of construct and content, as well as its responsiveness to chemotherapy.

On the basis of a former non-standardised questioning process in 2001 in our centre of tumour therapy, cancer patients described the following symptoms as their major complaints under chemo- and radiotherapy: 1) fatigue, 2) lack of motivation, 3) asthenia, 4) sleepiness, 5) lack of concentration and 6) cogitation, 7) disturbance of memory, 8) depressive symptoms, 9) visual, 10) acoustic, 11) olfactory and 12) gustatory hypersensitivity, 13) feeling indifferent, 14) feeling being not really present, 15) feeling not being coherent, 16) feeling discouraged, .17) feeling uncomfortable, 18) doing activities in a "mechanical manner", 19) having cold hands and feet, 20) often and quick freezing. The symptoms 1 – 7 were integrated in the parallel development process in the CFS-D 19, the symptoms 9–13 have been integrated in the questionnaire as single items.

Based on the symptoms 13 – 20, a group of experts (oncologist, internist, gastroenterologist, somnologist, general practitioner and statistician) formulated twelve items on the topics of meaningfulness, manageability and resilience in dealing with cancer disease and formation of perspective. According to our experience in cancer patients, we also integrated items on heat regulation, because a feeling of comfort and well-being is often associated with good thermoregulation being a precondition on the subject of inner coherence.

We were able to develop a short inventory on internal coherence (ICS) with a 2-factor structure – with the factors 1) inner resilience and coherence and 2) thermo coherence – with good to very good internal consistencey 21 and a sufficient – good test-retest reliability. As the initial expert rating for item generation was based on a previous cancer patient symptoms list, we renounced designing the study further patient reports and interviews. The responsiveness of the ICS was tested with chemotherapy treatment:

As the decrease in quality of life, or the increase in adverse events (AE) during chemotherapy respectively is well known 22 chemotherapy sensitivity (responsiveness) in the pooled B and C group was documented. Moreover, compared to the SRQ according to Grossarth-Maticek, the ICS sum scale and subscales show a better sensitivity for tumour patients in study 1 12. During chemo- or radiotherapy, the 'locus of disease control' is completely externalised, and thus measures of "self-autonomy" should be low. Even after chemotherapy, a more depressive state of "self-competence" may persist in several patients, particularly those with a poorer prognosis. The scale "Inner resilience and coherence" in fact was strongly associated with emotional functioning and depression and thus is expected to be a more sensitive measure of the stressful situations, but it did not correlate with tumour stage in our data. In study 2, compared to the EORTC quality of life subscales with 42% significant test results, the ICS showed in 83% significant test results. Interestingly, the EORTC show above all chemotherapy sensitivity in physical, cognitive and role functioning and not in the scales being strongly correlated with the ICS, as emotional functioning and only at one point in the global health scale. This could be related to the individual self-management. Hence, the ICS as a scale capturing the individual skills of adaptation could be more sensitive for responsiveness as the fixed passive emotional functioning HRQOL-measure.

High ICS, including high inner resilience and coherence and thermo coherence level, are consistent with higher self-regulation, autonomic regulation, quality of life, lower depression and anxiety, along with better perception of health and quality of life (table 5), which emphasizes the salutogenetic significance. On the other hand, lower ICS points towards oncological morbidity, worse performance-index, more chemotherapeutical side effects and increase in symptoms, as well as reduced salutogenetic counter-regulation (table 4). Even if thermo coherence correlations coefficients to the convergence criteria are rather moderate until low, there is face validity that thermal comfort influence not only quality of life and a feeling of coherence 15. There are further data showing that feeling cold and cold hands are well known distinctive side-effects under chemotherapy 23. To what extent an accumulation of risk factors is involved remains to be clarified.

Antonovsky's Sense of Coherence Scale (SOC) is a reliable, valid and transculturally common instrument 24 which surveys long-term life orientation and beliefs, partly looking backwards, partly looking into the future, which reflect the understandability, importance and manageability of life events and stressors 89. According to Antonovsky, SOC stabilises as a trait during adolescence 6; however, new empirical data show changes following interventions and life events 1025. It has been very clearly shown that the focus of the SOC scale is not suitable for the capture of current, clinically relevant feeling and state of coherence for clinical questions in internal oncological patients, because of the very backward-looking, general style of questions and the face validity 24.

Our ICS scale refers to the previous week and queries perception of comfort and health; questions on inner balance, particularly with respect to the ability of problem solving, security and inner congruence and resilience in terms of importance and manageability, and two additional items addressing perceptions of coldness/chillness and warmth ('thermo coherence'). In the moderate correlation of the two items of the thermo coherence subscale with the inner resilience and coherence subscale and self-regulation, we recognized a first confirmation of our hypothesis that thermoregulation and coherence in cancer patients could be related. Particularly, because tolerance of cold is moderately associated with less perspiration and high level thermo coherence which could be linked with the thermo-regulatory threshold between perspiration and vasoconstriction is depending on circadian rhythm, vigilance, personality coherence and gender 26. Hence, we decided to let both subscales integrated in the ICS scale, but this factor structure should be controlled with a larger number of patients. The recorded higher sensitivity of the ICS to differentiate between cancer patients and healthy controls as compared to self-regulation indicates a higher cancer sensitivity. To what extent the postulated cancer and treatment sensitivity of the ICS in contrast to the SOC questionnaire is cancer specific, remains to be verified in further studies.

A limitation of SOC is that the three-factor structure, as postulated by Antonovsky, could not be reproduced and factor-loading pattern are varying significantly in the different languages (2728. Moreover, the scale was mainly used and validated sociologically, socio-medically and psychiatrically 24. As most existing studies are cross-sectional studies, Antonovsky's basic assumption that the SOC is a principal determinant of health in terms of an ability to maintain particularly mental health despite of significant 'stressors', has not yet been sufficiently verified. Even if the data generated in the process show moderate to strong negative correlation between SOC on the one hand and anxiety, depression and distress on the other hand, as well as positive correlations to quality of life and subjectively gauged health, in particular mental health, there is still controversial discussion if SOC is an independent predictor for anxiety and depression or depends on un-existence of anxiety and depression 2927. In earlier prospective studies, the results were initially inconsistent 30, but now there are studies which seem to have a prognostic implication, amongst others, for cardiovascular mortality 31, for the risk of stroke 32, as well as a 46% increased prevalence of Diabetes mellitus Type 2 over a period of 17 years was associated with weak SOC 33.

Recently a large Finnish study showed a marginally higher 12-year cancer incidence with lower SOC in elderly 34. The EPIC-Norfolk-Study has also shown that lower SOC is associated with an increased global mortality and cancer mortality 31. These results match a cross-sectional study from Hawaii which systematically examined oncological patients with unusually long survival rates which did not differ from a control group with regards to their quality of life but only with regards to their SOC levels 7. These results are concordant with higher life expectancy of cancer patients with higher self-regulation level as compared to matched pairs – with an additional positive effect discovered amongst those receiving complementary mistletoe therapy 35. In fact, we can confirm strong correlations between the SRQ and the ICS and inner resilience and coherence scale and moderate with the thermo coherence scale. Despite these interesting results which indicate a positive influence of changing behaviour to reach goal and well-being orientated lifestyle in the context of salutogenesis on cancer incidence and progression, the importance of the SOC in large prospective studies has not yet been conclusively validated and requires further validation. The clinical and prospective importance of the new ICS remains to be clarified in future studies, but we intend to use it to capture more appropriately inner attitudes in palliative and disease-free cancer patients under chemo or mistletoe therapy, and to measure the influence of psychosocial support with this cancer specific individual skills of adaptation detecting tool.

There are significant limitations in our study in the lack of parallel recording of the SOC scale in the first and second part of the study. In unpublished data of our group, ICS correlates in cancer patients under treatment moderately with the SOC scales (comprehensibility: r = 0.50, meaningfulness: r = 0.49, manageability: r = 0.47 (all p < 0.05) indicating clearly the difference of the SOC, being a trait-marker and ICS as a more clinical tool referring to the last week. It must also be mentioned that the ten items of the ICS only query comprehensibility indirectly. In the second part of the study, we used a 1-side Wilcoxon test for measuring chemotherapy sensitivity of the scale because of clear hypothesis that ICS scores will decrease during chemotherapy and raise afterwards, and to minimize alpha-error due to the small patient number and because of concomitant mistletoe therapy already reducing side-effects of chemotherapy 3637. Hence, we accepted a potential over-estimation of the beta-error. The correlative associations between ICS and its subscales, anxiety and depression scale are rather less strong than with the SOC; Geyer 38 discusses to what extent the SOC would be largely dependent on symptoms of anxiety and depression (♂: r = 0.42, ♀: r = 0.53 – 0.85). Nevertheless, further studies should clarify if ICS is more than simply the absence of anxiety and depression.

The development of an Internal Coherence Scale (ICS) was achieved with good to very good reliability. First validity tests showed good convergence (Self-regulation), concurrence and discriminant validity between cancer patients and healthy control and confirmed a good responsiveness of the ICS during cancer treatment. Therefore, ICS could be an interesting instrument to capture the feeling of inner coherence and resilience among cancer patients. Further studies to confirm the scale structure and clinical relevance are required.

The authors declare that they have no competing interests.

MK, MG, HBvL, FS, MR designed the questionnaire, MK, MR performed statistical analysis, MK, AB, HM drafted the manuscript; HBvL, MG, GF participated in editing the manuscript. All authors read and approved the final manuscript.