Post-mastectomy radiotherapy in pT3N0M0 breast cancer: is it needed?

It is not been established whether breast cancer patients who have a primary tumor 5 cm or larger but no axillary nodal or distant metastases at the time of the diagnosis (pT3N0M0) benefit from post-operative radiation therapy after mastectomy.

We identified 81 patients with T3N0M0 breast cancer out of the total of 4190 breast cancer patients treated in one university radiotherapy department from 1987 to 1994 from the department patient registry, and examined the clinical records and histopathological slides.

Only 38 of the 81 patients had true pT3N0M0 breast cancer after the review (0.9% of the 4190 new breast cancer patients registered in the department from 1987 to 1994). Three (60%) of the five patients who were not treated with post-operative radiation therapy developed locoregional recurrence of breast cancer as compared with only three (9%) of the 33 patients who were given post-operative radiotherapy during a median follow-up of 58 months (P = 0.0003). Patients who were given post-operative radiotherapy had a better distant disease-free survival rate (P = 0.04) and overall survival rate (P = 0.03) than the ones who were not treated with radiation therapy after surgery. Of the 29 patients who had chest wall irradiation only, one had in-field recurrence at the surgical scar, one both at the scar and the unirradiated axilla, and only one (3%) solely in the axilla.

Patients with true pT3N0M0 breast cancer are rare. The results suggest that women with pT3N0M0 breast cancer benefit from post-operative radiotherapy, but the value of irradiating the dissected ipsilateral axilla remains unsettled.