Early detection of breast cancer rectifies inequality of breast cancer outcomes.

OBJECTIVES: To explain apparent differences among mammography screening services in Sweden using individual data on participation in screening and with breast cancer-specific survival as an outcome. METHODS: We analysed breast cancer survival data from the Swedish Cancer Register on breast cancer cases from nine Swedish counties diagnosed in women eligible for screening. Data were available on 38,278 breast cancers diagnosed and 4312 breast cancer deaths. Survival to death from breast cancer was estimated using the Kaplan-Meier estimate, for all cases in each county, and separately for cases of women participating and not participating in their last invitation to screening. Formal statistical comparisons of survival were made using proportional hazards regression. RESULTS: All counties showed a reduction in the hazard of breast cancer death with participation in screening, but the reductions for individual counties varied substantially, ranging from 51% (95% confidence interval 46-55%) to 81% (95% confidence interval 74-85%). Survival rates in nonparticipating women ranged from 53% (95% confidence interval 40-65%) to 74% (95% confidence interval 72-77%), while the corresponding survival in women participating in screening varied from 80% (95% confidence interval 77-84%) to 86% (95% confidence interval 83-88%), a considerably narrower range. CONCLUSIONS: Differences among counties in the effect of screening on breast cancer outcomes were mainly due to variation in survival in women not participating in screening. Screening conferred similarly high survival rates in all counties. This indicates that the performance of screening services was similar across counties and that detection and treatment of breast cancer in early-stage reduces inequalities in breast cancer outcome.

Mammography screening reduces rates of advanced and fatal breast cancers: Results in 549,091 women.

BACKGROUND: It is of paramount importance to evaluate the impact of participation in organized mammography service screening independently from changes in breast cancer treatment. This can be done by measuring the incidence of fatal breast cancer, which is based on the date of diagnosis and not on the date of death. METHODS: Among 549,091 women, covering approximately 30% of the Swedish screening-eligible population, the authors calculated the incidence rates of 2473 breast cancers that were fatal within 10 years after diagnosis and the incidence rates of 9737 advanced breast cancers. Data regarding each breast cancer diagnosis and the cause and date of death of each breast cancer case were gathered from national Swedish registries. Tumor characteristics were collected from regional cancer centers. Aggregated data concerning invitation and participation were provided by Sectra Medical Systems AB. Incidence rates were analyzed using Poisson regression. RESULTS: Women who participated in mammography screening had a statistically significant 41% reduction in their risk of dying of breast cancer within 10 years (relative risk, 0.59; 95% CI, 0.51-0.68 [P < .001]) and a 25% reduction in the rate of advanced breast cancers (relative risk, 0.75; 95% CI, 0.66-0.84 [P < .001]). CONCLUSIONS: Substantial reductions in the incidence rate of breast cancers that were fatal within 10 years after diagnosis and in the advanced breast cancer rate were found in this contemporaneous comparison of women participating versus those not participating in screening. These benefits appeared to be independent of recent changes in treatment regimens.

Prospective blinded surveillance screening of Swedish women with increased hereditary risk of breast cancer.

PURPOSE: To evaluate the sensitivity and specificity of different screening modalities in women with a family history of breast cancer. METHODS: Our blinded, prospective, comparative cohort analysis included three types of screening, mammography, ultrasound, and clinical breast examination once per year for 6 years. Eligible patients for this study were healthy women with ≥ 17% lifetime risk of breast cancer or with a mutation in BRCA1 or BRCA2. RESULTS: A total of 632 women were screened between 2002 and 2012 (each for 6 years). During the study, 30 women were diagnosed with breast cancer, with 10 of these diagnoses occurring between screening visits, and six of the 10 diagnosed women were gene carriers. The clinical presentation for the women diagnosed with breast cancer was followed until 2017. No consistent patterns for the diagnostic capacity of the different screening modalities were found, although mammography showed low sensitivity, whereas ultrasound showed better sensitivity in three of the six rounds. The specificity was high in mammography and improved in ultrasound over time. Most importantly, clinical breast examination provided no additional information toward the diagnosis of breast cancer. CONCLUSION: Neither mammography nor ultrasound performed yearly were sensitive enough as standalone modalities, although high specificity was confirmed. Our findings indicate that high risk (> 29% life time risk) individuals and gene carriers can be screened biannually, using the same protocol as used in mutation carriers. Our results also suggest that low-risk groups (< 20%) may continue to be referred to population mammography screening program, while clinical breast examination may be omitted in all risk groups, and could be optional in gene carriers.

Long-term functional and radiological pulmonary changes after radiation therapy for breast cancer.

BACKGROUND: We assessed late functional and radiological pulmonary changes in breast cancer patients after a median of 11 years following radiotherapy (RT). MATERIAL AND METHODS: Seventy women who received adjuvant loco-regional RT for breast cancer during November 1994-May 1998 accepted to participate in this follow-up study. Pulmonary function tests (PFTs) (n = 56) were compared to pre-RT examinations and diagnostic computer tomography (CT) of the lungs (n = 70) were performed and compared to four months post-RT examinations. RESULT: The median-matched vital capacity (VC), forced expiratory volume in one second (FEV1), and total lung capacity (TLC) were reduced 15%, 9%, and 7%, respectively, at the long-term follow-up (p < 0.001). We could not, however, detect a correlation between ipsilateral V20 and VC-changes. Diffusion capacity (DLCO) appeared to improve compared with the pre-RT baseline level probably due to transient chemotherapy-induced toxicity. The median-matched percentage of the predicted DLCO 11 years after RT was, however, only 86%, indicating a chronic therapy-induced reduction also of this metric. According to the Arriagada classification, ipsilateral V20 and long-term CT-changes showed a significant correlation (rs: 0. 57; p < 0.001) in a small subset of the women. CONCLUSION: A chronic clinically significant reduction of PFTs compared to pre-RT values and CT-changes four months after RT were still detectable after a median follow-up of 11 years. There was a statistical correlation between V20 and abnormalities on CT but no statistical correlation between V20 and VC-changes.

Pitfall in assessing the size of tumor phantoms on mammograms.

BACKGROUND: Tumor size is crucial for clinical management and prognosis of breast malignancies. MATERIALS AND METHODS: The gold standard-size of 12 tumor phantoms was assessed at The Department of Production Engineering. Subsequently, with a conventional ruler, seven experienced mammographers measured the largest diameter of the 12 devices in two independent trials. RESULTS: In the first trial, 30% (n=25) of the 84 values given by the seven mammographers failed to recreate the gold standard size by >1 mm and in the second, by 37% (31/84). Size was overestimated (>1 mm) in 9.5% (n=8) of 84 measurements in the first trial, and in 15.5% (14/84) in the second. Conversely, size was underestimated (>1 mm) in 20% (n=17) of 84 measurements in the first trial, and in 21% (18/84) in the second. Neither the age of the participants, nor their years of experience improved the obtained results. DISCUSSION: The method used here raised doubts concerning the ability of discriminating size among subgroups of T1 breast tumors in mammograms. According to the TNM staging system, T1 tumors (≤2.0 cm in greatest dimension) are subdivided into T1mic: microinvasion (≤0.1 cm), T1a (>0.1 cm but not more than 0.5 cm), T1b (>0.5 cm but not more than 1.0 cm) and T1c (>1.0 cm but not more than 2.0 cm in their greatest dimension). Since the TNM staging system for breast tumors is important in therapeutic decision making, it is crucial to develop a more reliable method for tumor size assessment.

Clinical experience of photon counting breast tomosynthesis: comparison with traditional mammography.

BACKGROUND: In two-dimensional mammography, a well-known problem is over- and underlying tissue which can either obstruct a lesion or create a false-positive result. Tomosynthesis, with an ability to layer the tissue in the image, has the potential to resolve these issues. PURPOSE: To compare the diagnostic quality, sensitivity and specificity of a single tomosynthesis mammography image and a traditional two-view set of two-dimensional mammograms and to assess the comfort of the two techniques. MATERIAL AND METHODS: One hundred and forty-four women, mainly chosen because of suspicious features on standard mammograms (76 malignant), had a single tomosynthesis image taken of one breast using a novel photon counting system. On average, the dose of the tomosynthesis images was 0.63 times that of the two-view images and the compression force during the procedure was halved. The resulting images were viewed by two radiologists and assessed both individually and comparing the two techniques. RESULTS: In 56% of the cases the radiologists rated the diagnostic quality of the lesion details higher in the tomosynthesis images than in the conventional images (and in 91% equal or higher), which means there is a statistically significant preference for the tomosynthesis technique. This included the calcifications which were rated as having better quality in 41% of the cases. While sensitivity was slightly higher for traditional mammography the specificity was higher for tomosynthesis. However, neither of these two differences was large enough to be statistically significant. CONCLUSION: The overall accuracy of the two techniques was virtually equal despite the radiologist's very limited experience with tomosynthesis images and vast experience with two-dimensional mammography. As the diagnostic quality of the lesion details in the tomosynthesis images was valued considerably higher this factor should improve with experience. The patients also favored the tomosynthesis examination, rating the comfort of the procedure as much higher than regular mammography which might affect screening attendance.

Reduction of radiation pneumonitis by V20-constraints in breast cancer.

INTRODUCTION: Adjuvant local-regional radiotherapy (LRRT) is routinely recommended for breast cancer patients. It is well known being related to pulmonary side-effects. We studied post-RT radiological changes on X-ray and CT, and correlated the findings with Quality of Life (QoL), common dosimetric factors and co-variates. The results were compared with a previously reported cohort of 137 irradiated women. METHODS: 88 women underwent chest X-ray and CT pre-and 4-5 months after 3-D planned LRRT, minimizing the dose to the ipsilateral lung to V20 < 30%. The lung field was divided into 3 regions and the development of post-RT density changes were graded (0-3). Patients with radiological changes were compared with non-responders. Clinical symptoms were registered and data on patient and treatment related co-variates were gathered prospectively. The ipsilateral lung dosimetric factors V13, V20, V30 and mean dose were calculated and QoL was assessed before and 4 months after RT. RESULTS: The use of dose-volume constraints significally reduced moderate-severe radiological changes on chest X-ray compared with our earlier study (Chi square trend test: p < 0.001). Symptomatic pneumonitis was also rare in the present study. No agreement was found between CT and chest X-ray as diagnostic tools for post-RT pneumonitis. V13 correlated independently with radiological changes on CT (logistic regression: p = 0.04; ROC area: 0.7). The Co-variates smoking habits, age, chemotherapy, endocrine or trastuzumab therapy did not influence the outcome on multivariate analysis. QoL changes in physical function, i.e. fatigue, dyspnoea were not detected but there was a trend for a worse recovery after chemotherapy in patients with high V13 (Spearman Rank Correlation: p < 0.05). CONCLUSIONS: The use of dose-volume constraints significantly reduced post-RT radiological changes on chest X-ray in LRRT for BC. The lung changes on CT were also generally limited when we used this strategy and was not always picked up on chest X-ray. Variation in V13 alone was correlated with occurrence of lung changes on CT.

Breast Cancer Screening Program in Stockholm County, Sweden - Aspects of Organization and Quality Assurance.

The population-based breast cancer screening program in Stockholm County was initiated in 1989. The program follows the recommendations issued by the Swedish Board of Health and Welfare, and is in agreement with guidelines from the European Commission. Individual data is available for all women in Stockholm County aged 40-69 years since initiation of the program in 1989. The participation rate exceeds 70%, the recall rate averages 3%, and the detection rate is 0.5%. The introduction of the breast cancer screening program in Stockholm County has reduced breast cancer mortality by 29% and among participants by 52%. The breast screening program is well organized and functioning, and well adapted to its purpose. Follow-up ensures a good quality process with the aim of reducing breast cancer mortality.

Quantitative assessment of lung density changes after 3-D radiotherapy for breast cancer.

Our aim was to reduce the rates of clinical and radiological pneumonitis in local-regional radiotherapy (RT) for breast cancer compared to a previous treatment series by applying a pre-planned lung dose volume constraint. 3-D dose planning was performed in 66 women with the aim of not exceeding an ipsilateral V20 of 30%. The patients were followed for short-term signs/symptoms of post-RT pneumonitis and radiological changes on chest CT 4 months after RT. Radiological abnormalities were scored with a CT-adapted modification of a semi-quantitative classification system originally proposed by Arriagada which accounts for severity and affected lung regions. The abnormal subvolumes were contoured and the mean doses were calculated. Three cases of mild and one case of moderate symptomatic pneumonitis were diagnosed. The mean V20 was higher in symptomatic than in unaffected patients, 29% vs. 24% (p =0.04). Mild/moderate radiological changes were frequently observed on CT in regions with average doses >30 Gy. According to multivariate modeling, a trend for association was found between the studied dosimetric factors V13, V20, V30 and mean lung dose, and moderate-severe changes on CT but not with patient specific covariates, e.g. chemotherapy or tamoxifen exposure. 3-D planned local-regional RT with a preplanned lung dose volume constraint of V20 <30% resulted in few cases of moderate symptomatic pneumonitis. Mild/moderate radiological changes were still detectable on CT in subvolumes receiving doses >30 Gy. Long-term follow-up for evaluation of possible late morbidity is warranted.

Early clinical and radiological pulmonary complications following breast cancer radiation therapy: NTCP fit with four different models.

OBJECTIVE: To fit four different NTCP (Normal Tissue Complication Probability) models to prospectively collected data on short-term pulmonary complications following breast cancer radiotherapy (RT). MATERIALS/METHODS: Four hundred and seventy-five breast cancer patients, referred to the Radiotherapy Department at Stockholm Söder Hospital (1994-1998) for adjuvant post-operative RT were prospectively followed for pulmonary complications 1, 4 and 7 months after the completion of RT. Eighty-seven patients with complete dose-volume histogram (DVH) of the ipsilateral lung were selected for the present analysis. Mean dose to the ipsilateral lateral lung ranged from 2.5 to 18Gy (median 12Gy). Three different endpoints were considered: (1) clinical pneumonitis scored according to CTC-NCIC criteria: asymptomatic (grade 0) vs grade 1 and grade 2; (2) radiological changes assessed with diagnostic chest X-ray: no/slight radiological changes vs moderate/severe; (3) radiological changes assessed with CT: no/slight vs moderate/severe. Four NTCP models were used: the Lyman model with DVH reduced to the equivalent uniform dose (LEUD), the Logit model with DVH reduced to EUD, the Mean Lung Dose (MLD) model and the Relative Seriality (RS) model. The data fitting procedure was done using the maximum likelihood analysis. The analysis was done on the entire population (n=87) and on a subgroup of patients treated with loco-regional RT (n=44). RESULTS: 24/87 patients (28%) developed clinical pneumonitis; 28/81 patients (35%) had radiological side effects on chest X-rays and 11/75 patients (15%) showed radiological density changes on Computed Tomography (CT). The analysis showed that the risk of clinical pneumonitis was a smooth function of EUD (calculated from DVH using n=0.86+/-0.10, best fit result). With LEUD, the relationship between EUD and NTCP could be described with a D(50) of 16.4Gy+/-1.1Gy and a steepness parameter m of 0.36+/-0.7. The results found in the overall population were substantially confirmed in the subgroup of patients treated with loco-regional RT. CONCLUSIONS: A large group of prospective patient data (87 pts), including grade 1 pneumonitis, were analysed. The four NTCP models fit quite accurately the considered endpoints. EUD or the mean lung dose are robust and simple parameters correlated with the risk of pneumonitis. For all endpoints the D(50) values ranged in an interval between 10 and 20Gy.

An isopropanolic extract of black cohosh does not increase mammographic breast density or breast cell proliferation in postmenopausal women.

OBJECTIVE: The aim of this study was to determine the effects of the isopropanolic extract of black cohosh (Remifemin) on mammographic breast density and breast epithelial proliferation in healthy, naturally postmenopausal women with climacteric symptoms. DESIGN: This was a prospective, open, uncontrolled drug safety study in which baseline status was compared with status after 6 months of treatment by blinded observers. A total of 74 women were treated with 40 mg black cohosh daily, and 65 women completed the study. Mammograms were performed, and breast cells were collected by percutaneous fine needle aspiration biopsies at baseline and after 6 months. Mammographic density was quantified according to the Wolfe classification or a percentage scale. Breast cell proliferation was assessed using the Ki-67/MIB-1 monoclonal antibody. Safety was monitored by adverse event reporting, laboratory assessments, and measurement of the endometrium by vaginal ultrasound. RESULTS: None of the women showed any increase in mammographic breast density. Furthermore, there was no increase in breast cell proliferation. The mean change +/- SD in proportion of Ki-67-positive cells was -0.5% +/- 2.4% (median, 0.0; 95% CI = -1.32 to 0.34) for paired samples. The mean change in endometrial thickness +/- SD was 0.0 +/- 0.9 mm (median, 0.0). A modest number of adverse events were possibly related to treatment, but none of these were serious. Laboratory findings and vital signs were normal. CONCLUSIONS: The findings suggest that the isopropanolic extract of black cohosh does not cause adverse effects on breast tissue. Furthermore, our data do not indicate to any endometrial or general safety concerns during 6 months of treatment.

Digitized assessment of mammographic breast density in patients who received low-dose intrauterine levonorgestrel in continuous combination with oral estradiol valerate: a pilot study.

OBJECTIVE: To perform a pilot study of the effects on the breast by low-dose intrauterine progestogen combined with estrogen. DESIGN: A prospective pilot study. SETTING: University hospital. PATIENT(S): Twenty postmenopausal women without any previous breast disorder. INTERVENTION(S): Women were treated with a low-dose intrauterine system releasing 20 microg/24 hours of levonorgestrel in continuous combination with 2 mg of oral E2 valerate. The effects on mammographic breast density, breast cell proliferation, and hormonal levels were followed for 18 months. MAIN OUTCOME MEASURE(S): Change in mammographic breast density and breast cell proliferation. Correlations with levels of hormones, growth factors, and binding proteins. RESULT(S): Three women showed an apparent increase in density. For the remaining 17 women the changes were only a few percent. Digitized assessment of density showed strong correlations with visual classification scales (rs = 0.96-0.97). There was no increase in proliferation as expressed by the percentage of MIB-1-positive breast cells in fine-needle aspiration biopsies. Increase in breast density displayed a positive correlation with patients age (rs = 0.52) and an inverse relationship with levels of E2 (rs = -0.50) and free T (rs = -0.50). CONCLUSION(S): Low-dose intrauterine administration progestogen may develop into an attractive alternative for hormonal therapy in postmenopausal women as endometrial protection may be achieved at very low systemic levels.

ROC curves and evaluation of radiation-induced pulmonary toxicity in breast cancer.

PURPOSE: To study clinical, radiologic, and physiologic pulmonary toxicity in 128 women after adjuvant radiotherapy (RT) for breast cancer in relation to dosimetric factors. METHODS AND MATERIAL: The patients underwent pulmonary function testing before and 5 months post-RT. Similarly, computer tomography of the chest was repeated 4 months post-RT and changes were scored with a semiquantitative system. Clinical symptoms were registered and scored according to Common Toxicity Criteria. All patients underwent three-dimensional dose planning, and the ipsilateral lung volume receiving > or = 13 Gy (V13), V20, and V30 were calculated. Multiple logistic or regression analyses were used for multivariate modeling. The relation between the dosimetric factors and side effects was also analyzed with receiver operating characteristic (ROC) curves. RESULTS: V20 was, according to multivariate modeling, the most important variable for the occurrence of the three studied side effects (p < 0.01). Age was also related to symptomatic and radiologic pneumonitis. Reduced pre-RT functional level was more common in patients developing symptomatic toxicity. The ROC areas for symptomatic pneumonitis in relation to V13, V20, and V30 were 0.69, 0.69, and 0.67, and for radiologic pneumonitis 0.85, 0.85, and 0.81. CONCLUSIONS: Our results support the use of three-dimensional planning aimed at minimizing the percent of incidentally irradiated lung volume to reduce pulmonary toxicity. Age was also correlated with post-RT side effects. According to ROC analysis, V20 could well predict the risk for radiologic pneumonitis for the studied semiquantitative model.

Pattern of participation in a cohort aged 50-60 years at first invitation to the service-screening programme with mammography in Stockholm county, Sweden.

BACKGROUND: Mammography screening can only be effective if a high proportion of the invited women attend. The aim of the present study was to search for patterns of participation in women who were invited to five consecutive rounds in a large screening programme. METHOD: Stockholm service-screening programme started 1989 and invites women between 50 and 69 years of age to mammography with 2 years interval. 64,852 women were eligible for an invitation to all five rounds during a 10-year period and were included in the study. RESULTS: More than 50% attended at all five rounds, and more than 70% at least four rounds. Only 8.5% were permanent non-participants. Women who attended at the first invitation round were more likely to attend also at subsequent rounds. CONCLUSIONS: It is possible to reach a high participation also in a large urban screening programme, but it seems that the invitation and examination at first round are most important in order to get a high compliance. Women who come at first round are more likely to come back for routine screening at a majority of subsequent rounds.

Different effects of tibolone and continuous combined estrogen plus progestogen hormone therapy on sex hormone binding globulin and free testosterone levels--an association with mammographic density.

OBJECTIVE: To compare the effects of tibolone and continuous combined hormone therapy on circulating sex steroids and their binding proteins and their relationship to mammographic density. STUDY DESIGN: A prospective, double-blind placebo-controlled study. A total of 166 postmenopausal women were equally randomized to receive tibolone 2.5 mg, estradiol 2 mg/norethisterone acetate 1 mg (E2/NETA) or placebo. Serum analyses of sex steroids, insulin-like growth factor (IGF-I) and binding proteins and assessment of mammographic breast density were performed at baseline and after 6 months of treatment. RESULTS: Estrogens were markedly increased and androgens decreased by E2/NETA. In contrast, tibolone had only a minor influence on circulating estrogens. Sex hormone binding globulin (SHBG) levels were reduced by 50%, while levels of androgens increased. Baseline values of estrone sulfate (E1S), around 1.0-1.1 nmol/l, were increased to 44.7 nmol/l by E2/NETA and to only 1.7 nmol/l by tibolone (p < 0.001). Mammographic breast density displayed a negative correlation with age and body mass index and a positive association with SHBG. After 6 months there was also a negative correlation with levels of free testosterone. Conclusion We found that tibolone and E2/NETA caused distinct differences in estrogen/androgen status and blood levels of possible breast mitogens. The negative association between free testosterone and mammographic density could be a possible explanation for tibolone having less influence on the breast.

Mammographic breast density, hormones, and growth factors during continuous combined hormone therapy.

OBJECTIVE: To study the effect on mammographic breast density of two different continuous combined regimens for hormone therapy. DESIGN: Randomized clinical study. SETTING: University hospital. PATIENT(S): Postmenopausal women without any previous history of breast disorder. INTERVENTION(S): The women received either estradiol valerate/dienogest or estradiol/norethisterone acetate. Mammograms and venous blood samples were obtained at baseline and after 6 months. MAIN OUTCOME MEASURE(S): Change in mammographic breast density. Correlations with levels of hormones, growth factors, and binding proteins. RESULT(S): An increase in mammographic density was recorded in approximately 50% of the women, and there were no differences between treatments. Increased density showed a positive correlation with estradiol, estrone, and sex hormone-binding globulin and showed a negative association to free T. Among hormonal factors, levels of free T were the most important for predicting increased density. CONCLUSION(S): Continuous combined hormone therapy with different progestogens has a marked impact on the breast.

Effects of tibolone and continuous combined hormone replacement therapy on mammographic breast density.

OBJECTIVE: Our purpose was to compare the effects of tibolone, continuous combined hormone replacement therapy, and placebo on mammographic breast density. STUDY DESIGN: A prospective, randomized, double-blind placebo-controlled study was performed. A total of 166 postmenopausal women were equally randomized to receive tibolone 2.5 mg, estradiol 2 mg/norethisterone acetate 1 mg (E(2)/NETA), or placebo. Mammograms were performed at baseline and after 6 months of treatment. Mammographic density was quantified according to the Wolfe classification and by the percentage area of the breast that had a dense pattern. RESULTS: An increase in mammographic density was much more common among women receiving continuous combined hormone replacement therapy (46%-50%) than among those receiving tibolone (2%-6%) and placebo (0%) treatment. The difference between E(2)/NETA and placebo was highly significant (P <.001). Treatment with tibolone did not differ from that with placebo. The relative risk of an increase in breast density for E(2)/NETA versus tibolone was found to be 8.3 (95% CI 2.7-25.0). CONCLUSION: An increase in mammographic density should be regarded as an unwanted side effect of hormone replacement therapy. In contrast to estrogen/progestogen treatment, tibolone seems to exert little stimulation of breast tissue.

Early response of lung in breast cancer irradiation: radiologic density changes measured by CT and symptomatic radiation pneumonitis.

PURPOSE: To quantify radiologic changes in the lung with CT after radiotherapy (RT) for breast cancer (BC) and to study their association with treatment techniques and symptomatic radiation pneumonitis (RP). METHODS AND MATERIALS: CT scans of the lungs were performed before and 4 months after RT in 121 BC patients treated with four different RT techniques. The changes in mean density (MDCs) were analyzed at two lung levels (i.e., the central and apical CT slice). The central CT slice was also analyzed with respect to the MDCs in the anterior third and anterior half of the ipsilateral lung area. In mastectomized patients who received chest wall RT with an en-face electron beam, the maximal depths for a range of isodose curves were measured. The occurrence of mild/moderate symptomatic RP was assessed prospectively 1, 4, and 7 months after RT. Data on covariates with potential confounding effect on RT-induced lung toxicity were also collected prospectively. RESULTS: In the entire study population, an association between the MDCs in the anterior third of the central CT slice and treatment technique (p <0.001) and symptomatic RP (p <0.001) was found. Among patients with chest wall treatment consisting of an en-face electron beam, the MDCs of the anterior third of the central CT slice correlated with the 35% isodose curve (16-30 Gy) (p = 0.046) and age (p <0.001). No association between post-RT lung density changes and pre-RT chemotherapy, concurrent tamoxifen intake, or smoking habits was found. Among patients treated with locoregional RT, an association was found between the MDCs in the anterior third of the central CT slice and the incidence of RP. MDCs in the apical CT slice, however, were not associated with RP. CONCLUSION: The results imply that short-term post-RT lung density changes and symptomatic RP were associated with RT techniques, total doses as low as 16-30 Gy, and increasing age. Structural changes in the central part of lung appeared to be more important for the development of RP than changes in the apex.