CHANGE IN MACROMOLECULAR-COMPOSITION OF INTERSTITIAL FLUID FROM SWOLLEN ARMS AFTER BREAST-CANCER-TREATMENT, AND ITS IMPLICATIONS

1. The pathophysiology of chronic arm oedema after treatment of breast cancer was investigated by collecting serum and subcutaneous intersti tial fluid from the affected and contralateral arms by the wick method (both arms) and by aspiration (oedematous arm). The fluids were analy sed for total protein, albumin, glycosaminoglycan and viscosity, and a rm volume was measured. 2. Total protein concentration in the aspirate d oedema fluid was 32.4+/-7.5 g/l (mean+/-SD throughout; n=39). Protei n concentration in wick fluid from the oedematous arm (35.8+/-7.3 g/l, n = 14) was not significantly different from that in aspirated fluid. The oedema protein concentrations were significantly lower than in wi ck fluid from the non-swollen arm (41.4+/-6.7 cmH2O, n=13, P<0.01, ana lysis of variance). This was surprising in view of the common assumpti on that, the condition being of lymphatic origin, the oedema protein c oncentration should be raised. 3. The ratio of aspirate protein concen tration to serum protein concentration showed a weak but highly signif icant negative correlation with the percentage increase in arm volume (r=-0.47, n = 35, P<0.005), again in contrast to conventional expectat ion. The demonstration of a reduced protein concentration in the swoll en arm did not therefore depend solely on a comparison with the wick c ontrol results. The volume increased by on average 33% and the ratio o f aspirate protein concentration to serum protein concentration averag ed 0.52+/-0.11 on the swollen side and 0.64+/-0.13 on the unaffected s ide. 4. Serum protein concentration in the patients with arm swelling (61.2+/-4.9 g/l) was significantly lower than that in postmastectomy p atients without this complication (65.0+/-6.2 g/l). Most of the decrea se occurred in the albumin fraction (oedema patients, 38.3+/-5.l g/l; control patients, 42.0+/-2.1 g/l). In oedema patients receiving the an ti-oestrogen tamoxifen serum albumin concentration was on average 2.3 g/l lower than in oedema patients not under medication (P<0.05, t-test ). 5. Glycosaminoglycan concentration in oedema fluid was 0.8+/-0.14 g /l (n = 21) and 75% was sulphated. Along with the plasma protein this raised the relative viscosity of the fluid to 1.34+/-0.16 (n = 11). 6. The reduction in interstitial protein concentration in the swollen ar m, contrary to expectation in lymphoedema, could be explained in sever al ways. One possible hypothesis in light of reported haemodynamic abn ormalities in such arms is that capillary pressure rises, increasing c apillary filtration rate. We conclude that the pathophysiology of post mastectomy oedema involves additional factors besides axillary node tr auma, and we suggest that input (filtration) as well as output (lymph flow) requires evaluation.