**3. Radiotherapy treatment regimens**

For women who had breast conserving surgery for an invasive breast cancer, radiotherapy was regarded as standard treatment and computer dose-planned photon beam (6 and/or 15 MV) treatment was used. Care was taken not to treat the ipsilateral lung and, in the case of left-sided breast cancers, the heart. The whole breast parenchyma was defined as the target and 2 Gray per fraction times 25 was delivered over 5 weeks. If the patient was younger than age 45 yrs or if extensive DCIS (>25% of tumor) was present, additional photon-boost was used against the tumor bed. The boost-target was treated with 2 Gy per fraction to a total of 10 - 16 Gray. If one or more lymph nodes were engaged with cancer, separate fields were directed to the ipsilateral axilla and supraclavicular fossa, 2 Gray per fraction x 25 was used. Treatment of the intramammary lymph nodes was considered if 4 or more of the axillary nodes were metastasized.

Computer dose-planned radiotherapy was used also for some patients treated with a mastectomy. The thoracic wall was treated with opposed tangential photon fields if the tumor was > 30 mm or multifocal or N1. Regional lymph nodes were treated according the rules described above. Boost treatment was given only in the rare instances when surgical radicality could not be achieved.

#### **4. Multifactor score of risk of recurrence**

Data were analysed by stepwise Cox proportional hazards regression to build up a multifactor score of risk of recurrence. Analyses were adjusted for age and epoch of diagnosis, as radiotherapy practices depended on these factors. After exclusion of those

maximum diameter less than 15 mm, with a view to developing an index of risk of local recurrence and possibly of identifying patient populations suitable and unsuitable for radiotherapy. The research was approved by the Ethics Committee of Falun Central

Mammograms were retrieved of all tumours of pathological size less than 15 mm, diagnosed in women aged 40-69 between 1977 and 1998 in Falun Central Hospital, Sweden. Of these, 425 were identified to have stellate appearance and either no calcifications or nonspecific calcifications on the mammogram. Patient charts were retrieved and additional pathological information was obtained on exact tumor size in mm, node status, tumor grade and histological type. Treatment details with respect to surgery, adjuvant radiotherapy, chemotherapy and hormonal therapy were also retrieved. In addition, we recorded age, date of diagnosis, mode of detection (screening or symptomatic) and follow-up details including

There was an average follow-up of 10.4 years to recurrence, death or last known date alive and disease-free, and a maximum follow-up of 27.9 years. The most recent date of follow-up was 20th March 2006. Local recurrence was defined as the occurrence of a histologically confirmed *in situ* or invasive carcinoma in the ipsilateral breast after treatment of the first

For women who had breast conserving surgery for an invasive breast cancer, radiotherapy was regarded as standard treatment and computer dose-planned photon beam (6 and/or 15 MV) treatment was used. Care was taken not to treat the ipsilateral lung and, in the case of left-sided breast cancers, the heart. The whole breast parenchyma was defined as the target and 2 Gray per fraction times 25 was delivered over 5 weeks. If the patient was younger than age 45 yrs or if extensive DCIS (>25% of tumor) was present, additional photon-boost was used against the tumor bed. The boost-target was treated with 2 Gy per fraction to a total of 10 - 16 Gray. If one or more lymph nodes were engaged with cancer, separate fields were directed to the ipsilateral axilla and supraclavicular fossa, 2 Gray per fraction x 25 was used. Treatment of the intramammary lymph nodes was considered if 4 or more of the

Computer dose-planned radiotherapy was used also for some patients treated with a mastectomy. The thoracic wall was treated with opposed tangential photon fields if the tumor was > 30 mm or multifocal or N1. Regional lymph nodes were treated according the rules described above. Boost treatment was given only in the rare instances when surgical

Data were analysed by stepwise Cox proportional hazards regression to build up a multifactor score of risk of recurrence. Analyses were adjusted for age and epoch of diagnosis, as radiotherapy practices depended on these factors. After exclusion of those

dates of local recurrence, death from breast cancer and death from other causes.

Hospital.

**2. Patient data obtained for analysis** 

breast cancer was completed.

axillary nodes were metastasized.

radicality could not be achieved.

**4. Multifactor score of risk of recurrence** 

**3. Radiotherapy treatment regimens** 

factors that were not statistically significant when adjusted for other variables, we used the final Cox regression model to estimate the absolute reductions in 15-year risk of recurrence (only 22% of subjects had follow-up in excess of 15 years).
