Source: Cancer. 2005 Jun 15;103(12):2447-54.
Authors: Santiago RJ, Harris EE, Qin L, Hwang WT, Solin LJ.
Affiliation: University of Pennsylvania, Philadelphia, PA.
In breast cancer, invasive lobular cancers (ILC) are rarer than invasive ductal cancers (IDC), and the majority of the large randomized trials establishing the efficacy of breast conserving treatment have been dominated by patients with ductal histology. A few retrospective studies have suggested that ILC has a higher local recurrence rate and recurrences are multifocal and multicentric. Therefore, some have questioned whether breast conserving treatment is also appropriate for lobular histology.
- Design: Retrospective analysis of breast cancer patients treated at the University of Pennsylvania
- Patients: Stage 1/II treated with breast conserving treatment between 1977 and 1995. Histology: 1093 patients with IDC and 55 patients with ILC
- Surgery: complete macroscopic tumor removal and axillary dissection
- Radiotherapy: whole breast megavoltage irradiation with tangents (median 46 Gy) followed by a boost (median 18 Gy). Regional nodal irradiation was done in 26% of patients
- Adjuvant chemotherapy and/or hormonal therapy was given in 49%
- Local recurrences were scored regardless of regional/distant disease status
- Median follow-up: 8.8 years (all); 10.2 years for patients with ILC
- The ILC and IDC patient groups were generally similar except the ILC's were more likely to be detected by physical exam, more likely to be pN0, more likely to have re-excision, and less likely to receive adjuvant chemotherapy.
- There were 9 local failures in patients with ILC (16%) and 118 local failures (11%) in patients with IDC
- Local failure rates at 5 and 10 years were: 14% and 18% for ILC; 6% and 12% for IDC
- Contralateral breast cancer rates at 5 and 10 years were: 4% and 12% for ILC; 3% and 8% for IDC
- Overall survival rates at 5 and 10 years were: 92% and 85% for ILC; 90% and 79% for IDC
- There were no statistically significant difference in rates of local failure, contralateral breast cancer, overall survival, or cause-specific survival (p all greater than 0.23)
- This is one of the largest series with long-term follow-up evaluating ductal vs. non-ductal histologies. Although the small numbers precluded detecting a small difference in outcomes between ILC and IDC, no large differences were observed. The authors contend that this study supports the routine use of breast conserving treatment in patients with ILC.
- The observation that ILC's were more likely to be detected by physical exam is consistent with other reports. ILC is more difficult to detect mammographically, possibly because ILC does not elicit much of a desmoplastic reaction. This may also account for the somewhat increased difficulty in ILC to obtain negative margins, requiring more re-excisions.
- Although patients with ILC trended toward slightly higher local recurrence rates, no large differences were detectable. The large size and long follow-up distinguish this work from similar retrospective studies. With even more patients and even longer follow-up, it may be possible to detect a statistically significant difference, but it probably would not be a clinically significant difference. In general, the local recurrence rates were low enough to advocate breast conserving treatment in ILC. As the authors also point out, recurrences would probably be even lower with more modern attention to margin status, receptor status, and more aggressive use of adjuvant systemic treatment.