An acute toxicity study on the effects of synchronous chemotherapy and radiotherapy in early stage breast cancer after conservative surgery.

One hundred and ninety-seven patients with early stage breast cancer, who were treated initially with conservative surgery, were evaluated prospectively for acute toxicity after completing post-operative irradiation. Eighty-seven of these patients had synchronous chemotherapy with the 3M regimen (mitoxantrone, methotrexate and Mitomycin-C) during radiotherapy. The results indicate that patients receiving chemotherapy and radiotherapy (CRT) showed no significant difference in acute skin toxicity (AST) when compared with those treated with radiotherapy alone (RTO), with an odds ratio (OR = 0.6) and 95% confidence intervals (0.3-1.1) of developing either a moderate or severe, compared with a mild, skin reaction. Even after controlling for other confounding factors, such as treatment technique and beam energy, patients treated with the supine technique using 6-10 MV photons still displayed no significant difference in AST, with 12/74 (16%) patients in the CRT group and 14/66 (21%) in the RTO group developing a moderate or severe skin reaction (OR = 0.7 (95% CI 0.3-1.7)). Four of the 87 patients treated with CRT developed symptomatic acute radiation pneumonitis, three of whom were found to have > 3 cm of lung length on their simulator or check films. The volume of lung included within the treatment field was found to be statistically significant (P = 0.005) in predicting the onset of radiation pneumonitis in the CRT group. None of these patients has suffered any symptomatic late lung toxicity. We conclude that synchronous chemotherapy and radiotherapy, when using the 3M regimen, is feasible for patients having adjuvant treatment for early stage breast carcinoma and there is no significant increase in AST. However, it is associated with an increase in acute radiation pneumonitis when a significant volume of lung is included within the radiation treatment field.