Strong correlation between specific heat capacity and water content in human tissues suggests preferred heat deposition in malignant tumors upon electromagnetic irradiation.

PURPOSE: Tumor perfusion is considered to be the principal factor determining the build-up of therapeutically effective thermal fields. This assumes that malignancies have lower perfusions than their homologous tissues. This assumption, however, ignores the fact that several tumor types have higher perfusions than their healthy counterparts. Additionally, flow changes upon hyperthermia (39-43 °C) are non-predictable and extremely heterogeneous. Therefore, modeling temperature distribution further requires a more robust parameter, different in malignancies and healthy tissues, i.e., water content (Cw), which highly determines thermal properties upon electromagnetic irradiation.

METHOD: Systematic literature reviews of Cw and specific heat capacities (cp) were conducted up to 28 February 2022, providing an updated, comprehensive data overview based on original manuscripts, reviews and databases.

RESULTS

Cw- and cp-values of cancers and their corresponding healthy tissues are presented. Strong correlations between these two parameters are described. In general, malignant tumors have distinctly higher Cw values than their homologous tissues. With increasing Cw in low-water-content normal tissues (<70 wt.%), cp rises exponentially from 1.5 to 3.3 J·g-1·K-1. In high-water-content normal tissues (≥70 wt.%), cp increases linearly from 3.5 to 3.8 J·g-1·K-1. In malignant tumors (>80 wt.%), cp rises linearly from 3.6 to 3.9 J·g-1·K-1. Cancers contain up to 27% more water than their tissues of origin and must be considered as 'high-capacitance-tissues'.

CONCLUSIONS

Hyperhydration of cancers result in higher cp-values, causing cancers to be better heat reservoirs than corresponding normal tissues upon electromagnetic irradiation. Reliable, tissue-/cancer-specific cp values must be considered when modeling temperature distributions in hyperthermic treatment.