Characteristics and Outcomes for Secondary Breast Cancer in Childhood, Adolescent, and Young Adult Cancer Survivors Treated with Radiation

Rapamycin prevents cyclophosphamide-induced ovarian follicular loss and potentially inhibits tumour proliferation in a breast cancer xenograft mouse model

STUDY QUESTION

To what extent and via what mechanism does the concomitant administration of rapamycin (a follicle activation pathway inhibitor and antitumour agent) and cyclophosphamide (a highly toxic ovarian anticancer agent) prevent cyclophosphamide-induced ovarian reserve loss and inhibit tumour proliferation in a breast cancer xenograft mouse model?

SUMMARY ANSWER

Daily concomitant administration of rapamycin and a cyclic regimen of cyclophosphamide, which has sufficient antitumour effects as a single agent, suppressed cyclophosphamide-induced primordial follicle loss by inhibiting primordial follicle activation in a breast cancer xenograft mouse model, suggesting the potential of an additive inhibitory effect against tumour proliferation.

WHAT IS KNOWN ALREADY

Cyclophosphamide stimulates primordial follicles by activating the mammalian target of the rapamycin (mTOR) pathway, resulting in the accumulation of primary follicles, most of which undergo apoptosis. Rapamycin, an mTOR inhibitor, regulates primordial follicle activation and exhibits potential inhibitory effects against breast cancer cell proliferation.

STUDY DESIGN, SIZE, DURATION

To assess ovarian follicular apoptosis, 3 weeks after administering breast cancer cells, 8-week-old mice were randomized into three treatment groups: control, cyclophosphamide, and cyclophosphamide + rapamycin (Cy + Rap) (n = 5 or 6 mice/group). Mice were treated with rapamycin or vehicle control for 1 week, followed by a single dose of cyclophosphamide or vehicle control. Subsequently, the ovaries were resected 24 h after cyclophosphamide administration (short-term treatment groups). To evaluate follicle abundance and the mTOR pathway in ovaries, as well as the antitumour effects and impact on the mTOR pathway in tumours, 8-week-old xenograft breast cancer transplanted mice were randomized into three treatment groups: vehicle control, Cy, and Cy + Rap (n = 6 or 7 mice/group). Rapamycin (5 mg/kg) or the vehicle was administered daily for 29 days. Cyclophosphamide (120 mg/kg) or the vehicle was administered thrice weekly (long-term treatment groups). The tumour diameter was measured weekly. Seven days after the last cyclophosphamide treatment, the ovaries were harvested, fixed, and sectioned (for follicle counting) or frozen (for further analysis). Similarly, the tumours were resected and fixed or frozen.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Terminal deoxynucleotidyl transferase dUTP nick end labelling (TUNEL) was performed to examine ovarian follicular apoptosis in the short-term treatment groups. All subsequent experiments were conducted in the long-term treatment groups. Tumour growth was evaluated using the tumour volume index. The tumour volume index indicates the relative volume, compared to the volume 3 weeks after tumour cell injection (at treatment initiation) set to 100%. Tumour cell proliferation was evaluated by Ki-67 immunostaining. Activation of the mTOR pathway in tumours was assessed using the protein extracts from tumours and analysed by western blotting. Haematoxylin and eosin staining of ovaries was used to perform differential follicle counts for primordial, primary, secondary, antral, and atretic follicles. Activation of the mTOR pathway in ovaries was assessed using protein extracts from whole ovaries and analysed by western blotting. Localization of mTOR pathway activation within ovaries was assessed by performing anti-phospho-S6 kinase (downstream of mTOR pathway) immunohistochemistry.

MAIN RESULTS AND THE ROLE OF CHANCE

Ovaries of the short-term treatment groups were resected 24 h after cyclophosphamide administration and subjected to TUNEL staining of apoptotic cells. No TUNEL-positive primordial follicles were detected in the control, Cy, and Cy + Rap groups. Conversely, many granulosa cells of growing follicles were TUNEL positive in the Cy group but negative in the control and Cy + Rap groups. All subsequent experimental results were obtained from the long-term treatment groups. The tumour volume index stabilized at a mean of 160-200% in the Cy group and 130% in the Cy + Rap group throughout the treatment period. In contrast, tumours in the vehicle control group grew continuously with a mean tumour volume index of 600%, significantly greater than that of the two treatment groups. Based on the western blot analysis of tumours, the mTOR pathway was activated in the vehicle control group and downregulated in the Cy + Rap group when compared with the control and Cy groups. Ki-67 immunostaining of tumours showed significant inhibition of cell proliferation in the Cy + Rap group when compared with that in the control and Cy groups. The ovarian follicle count revealed that the Cy group had significantly fewer primordial follicles (P < 0.001) than the control group, whereas the Cy + Rap group had significantly higher number of primordial follicles (P < 0.001, 2.5 times) than the Cy group. The ratio of primary to primordial follicles was twice as high in the Cy group than in the control group; however, no significant difference was observed between the control group and the Cy + Rap group. Western blot analysis of ovaries revealed that the mTOR pathway was activated by cyclophosphamide and inhibited by rapamycin. The phospho-S6 kinase (pS6K)-positive primordial follicle rate was 2.7 times higher in the Cy group than in the control group. However, this effect was suppressed to a level similar to the control group in the Cy + Rap group.

LARGE SCALE DATA

None.

LIMITATIONS, REASONS FOR CAUTION

The combinatorial treatment of breast cancer tumours with rapamycin and cyclophosphamide elicited inhibitory effects on cell proliferative potential compared to cyclophosphamide monotherapy. However, no statistically significant additive effect was observed on tumour volume. Thus, the beneficial antitumour effect afforded by rapamycin administration on breast cancer could not be definitively proven. Although rapamycin has ovarian-protective effects, it does not fully counteract the ovarian toxicity of cyclophosphamide. Nevertheless, rapamycin is advantageous as an ovarian protective agent as it can be used in combination with other ovarian protective agents, such as hormonal therapy. Hence, in combination with other agents, mTOR inhibitors may be sufficiently ovario-protective against high-dose and cyclic cyclophosphamide regimens.

WIDER IMPLICATIONS OF THE FINDINGS

Compared with a cyclic cyclophosphamide regimen that replicates human clinical practice under breast cancer-bearing conditions, the combination with rapamycin mitigates the ovarian follicle loss of cyclophosphamide without interfering with the anticipated antitumour effects. Hence, rapamycin may represent a new non-invasive treatment option for cyclophosphamide-induced ovarian dysfunction in breast cancer patients.

STUDY FUNDING/COMPETING INTEREST(S)

This work was not financially supported. The authors declare that they have no conflict of interest.

Survival After Contralateral Secondary Breast Cancer by Age Group in California

PURPOSE

Breast cancer (BC) is the most common secondary cancer and has poorer survival than primary BC (pBC) after any prior malignancy. For BC survivors, developing a contralateral secondary BC (CSBC) is the most frequent second-cancer event and is currently treated similarly to pBC. Identifying survival differences between pBC and CSBC could influence future counseling and treatments for patients with CSBC.

METHODS

Women (≥15 years) diagnosed with pBC from 1991 to 2015 in the California Cancer Registry (n = 377,176) were compared with those with CSBC (n = 15,586) by age group (15-39 years, n = 406; 40-64 years, n = 6814; ≥ 65 years, n = 8366). Multivariable logistic regression models assessed factors associated with CSBC. Multivariable Cox proportional hazards regression models assessed BC-specific survival (BCSS), while accounting for the competing risk of death.

RESULTS

Across all ages, CSBC patients were more likely to have smaller tumors (T2 vs. T1a; 15-39 yeras: OR 0.25, CI 0.16-0.38; 40-64 years: OR 0.41, CI 0.37-0.45; ≥ 65 years: OR 0.46, CI 0.42-0.51) and lymph node-negative disease (positive vs. negative; 15-39 years: OR 0.86, CI 0.69-1.08; 40-64 years: OR 0.88, CI 0.83-0.93; ≥ 65 years: OR 0.89, CI 0.84-0.94). Additionally, CSBC was associated with worse survival compared with pBC across all ages (15-39 years: HR 2.73, CI 2.30-3.25; 40-64 years: HR 2.13, CI 2.01-2.26; ≥ 65 years: HR 1.52, CI 1.43-1.61).

CONCLUSION

BCSS is worse among all women diagnosed with CSBC compared with pBC, with the strongest impact seen in adolescent and young adult women. Worse survival after CSBC, despite associations with smaller tumors and lymph node negativity, suggests that CSBC may need eventual treatment reconsideration.

Racial and Ethnic Disparities in Survival Among People With Second Primary Cancer in the US

Importance

Comprehensive data for racial and ethnic disparities after second primary cancers (SPCs) are lacking despite the growing burden of SPCs.

Objective

To quantify racial and ethnic disparities in survival among persons with SPCs.

Design, Setting, and Participants

This population-based, retrospective cohort study used data from 18 Surveillance, Epidemiology, and End Results registries in the US for persons diagnosed with the most common SPCs at age 20 years or older from January 1, 2000, to December 31, 2013 (with follow-up through December 31, 2018). Data were analyzed between January and April 2023.

Exposure

Race and ethnicity (Hispanic, non-Hispanic Asian or Pacific Islander, non-Hispanic Black, and non-Hispanic White).

Main Outcomes and Measures

The main outcomes were 5-year relative survival and cause-specific survival. Cause-specific hazard ratios (HRs) were calculated for death from cancer or cardiovascular disease (CVD) in each racial and ethnic minority population compared with the White population overall and stratified by SPC type, with adjustment for sex, year and age at SPC diagnosis, and prior cancer type and stage (baseline model) and additionally for county attributes (household income, urbanicity), SPC characteristics (stage, subtype), and treatment.

Results

Among 230 370 persons with SPCs (58.4% male), 4.5% were Asian or Pacific Islander, 9.6% were Black, 6.4% were Hispanic, and 79.5% were White. A total of 109 757 cancer-related deaths (47.6%) and 18 283 CVD-related deaths (7.9%) occurred during a median follow-up of 54 months (IQR, 12-93 months). In baseline models, compared with the White population, the risk of cancer-related death overall was higher in the Black (HR, 1.21; 95% CI, 1.18-1.23) and Hispanic (HR, 1.10; 95% CI, 1.07-1.13) populations but lower in the Asian or Pacific Islander population (HR, 0.93; 95% CI, 0.90-0.96). When stratified by 13 SPC types, the risk of cancer-related death was higher for 10 SPCs in the Black population, with the highest HR for uterine cancer (HR, 1.87; 95% CI, 1.63-2.15), and for 7 SPCs in the Hispanic population, most notably for melanoma (HR, 1.46; 95% CI, 1.21-1.76). For CVD-related death, the overall HR was higher in the Black population (HR, 1.41; 95% CI, 1.34-1.49), with elevated risks evident for 11 SPCs, but lower in the Asian or Pacific Islander (HR, 0.75; 95% CI, 0.69-0.81) and Hispanic (HR, 0.90; 95% CI, 0.84-0.96) populations than in the White population. After further adjustments for county attributes and SPC characteristics and treatment, HRs were reduced for cancer-related death and for CVD-related death and associations in the same direction remained.

Conclusions and Relevance

In this cohort study of SPC survivors, the Black population had the highest risk of both death from cancer and death from CVD, and the Hispanic population had a higher risk of death from cancer than the White population. Attenuations in HRs after adjustment for potentially modifiable factors highlight opportunities to reduce survival disparities among persons with multiple primary cancers.

Subsequent primary cancer risk among five-year survivors of adolescent and young adult cancers

BACKGROUND

A comprehensive examination of the incidence and mortality of subsequent primary cancers (SPCs) among adolescent and young adult (AYA) cancer survivors in the US is lacking.

METHODS

Cancer incidence and mortality among 170,404 ≥ 5-year cancer survivors aged 15-39 years at first primary cancer diagnosis during 1975-2013 in 9 Surveillance, Epidemiology, and End Results registries were compared to those in the general population using standardized incidence ratio (SIR), absolute excess incidence (AEI), standardized mortality ratio (SMR), and absolute excess mortality (AEM).

RESULTS

During a mean follow-up of 14.6 years, 13,420 SPC cases and 5,008 SPC deaths occurred among survivors (excluding the same-site as index cancer), corresponding to 25% higher incidence (95%CI = 1.23-1.27; AEI = 10.8 per 10,000) and 84% higher mortality (95%CI = 1.79-1.89; AEM = 9.2 per 10,000) than that in the general population. Overall SPC risk was statistically significantly higher for 20 of 29 index cancers for incidence and 26 for mortality, with the highest SIR among female Hodgkin lymphoma survivors (SIR = 3.05, 95%CI = 2.88-3.24; AEI = 73.0 per 10,000) and the highest SMR among small intestine cancer survivors (SMR = 6.97, 95%CI = 4.80-9.79; AEM = 64.1 per 10,000). Type-specific SPC risks varied substantially by index cancers; however, SPCs of the female breast, lung, and colorectum combined constituted 36% of all SPC cases and 39% of all SPC deaths, with lung cancer alone representing 11% and 24% of all cases and deaths, respectively.

CONCLUSION

AYA cancer survivors are almost twice as likely to die from a new primary cancer as the general population, highlighting the need for primary care clinicians to prioritize cancer prevention and targeted surveillance strategies in these individuals.

A Review of Breast Cancer Risk Factors in Adolescents and Young Adults

Simple Summary

Cancer diagnosed in patients between the ages of 15 and 39 deserves special consideration. Diagnoses within this cohort of adolescents and young adults include childhood cancers which present at an older age than expected, or an early presentation of cancers that are typically observed in older adults, such as breast cancer. Cancers within this age group are associated with worse disease-free and overall survival rates, and the incidence of these cases are rising. Knowing an individual’s susceptibility to disease can change their clinical management and allow for the risk-testing of relatives. This review discusses the risk factors that contribute to breast cancer in this unique cohort of patients, including inherited genetic risk factors, as well as environmental and lifestyle factors. We also describe risk models that allow clinicians to quantify a patient’s lifetime risk of developing disease.

Abstract

Cancer in adolescents and young adults (AYAs) deserves special consideration for several reasons. AYA cancers encompass paediatric malignancies that present at an older age than expected, or early-onset of cancers that are typically observed in adults. However, disease diagnosed in the AYA population is distinct to those same cancers which are diagnosed in a paediatric or older adult setting. Worse disease-free and overall survival outcomes are observed in the AYA setting, and the incidence of AYA cancers is increasing. Knowledge of an individual’s underlying cancer predisposition can influence their clinical care and may facilitate early tumour surveillance strategies and cascade testing of at-risk relatives. This information can further influence reproductive decision making. In this review we discuss the risk factors contributing to AYA breast cancer, such as heritable predisposition, environmental, and lifestyle factors. We also describe a number of risk models which incorporate genetic factors that aid clinicians in quantifying an individual’s lifetime risk of disease.

Secondary Breast Cancer Sociodemographic Characteristics and Survival by Age Group

Background

Secondary cancers account for 16% of all new cancer diagnoses, with breast cancer (BC) the most common secondary cancer. We have shown that secondary BC has unique characteristics and decreased survival compared with primary BC in adolescent and young adults (AYA; 15–39 years old). However, older BC populations are less well studied.

Methods

Females (age ≥ 15 years) diagnosed with primary BC during 1991–2015 (n = 377,167) and enrolled in the California Cancer Registry were compared with those with secondary BC (n = 37,625) by age (15–39, 40–64, ≥ 65 years). We examined BC-specific survival (BCSS) accounting for other causes of death as a competing risk using multivariable Cox proportional hazards regression.

Results

Most secondary BC patients were of older age (15–39, n = 777; 40–64, n = 15,848; ≥ 65, n = 21,000). Compared with primary BC treatment, secondary BCs were more often treated with mastectomy and less often with chemotherapy and/or radiation. BCSS was shorter in secondary BC patients than primary BC patients, but the survival difference between secondary and primary BC diminished with age [15–39 hazard ratio (HR): 2.09, 95% confidence interval (CI) 1.83–2.39; 40–64 HR: 1.51; 95% CI 1.44–1.58; ≥ 65 HR: 1.14; 95% CI 1.10–1.19]. Survival differences were most pronounced in women with hormone receptor positive disease and Hispanic and Asian/Pacific Islanders 40–64 years of age.

Conclusions

When BC is diagnosed following a prior cancer of any organ site, BCSS is worse than when compared with patients for whom BC is the primary diagnosis, suggesting that we may need to tailor our treatments for women with secondary BC.