Radiation doses received by major organs at risk in children and young adolescents treated for cancer with external beam radiation therapy: a large-scale study from 12 European countries

BACKGROUND

Childhood cancer survivors are at high risk of long-term iatrogenic events, in particular those treated with radiotherapy. The prediction of risk of such events is mainly based on the knowledge of the radiation dose received to healthy organs and tissues during treatment of childhood cancer diagnosed decades ago.

PURPOSE

We aimed to set up a standardised organ dose table in order to help former patients and clinician in charge of long term follow-up clinics.

MATERIAL AND METHODS

We performed whole body dosimetric reconstruction for 2646 patients from 12 European Countries treated between 1941 and 2006 (median: 1976). Most planning were 2D or 3D, 46% of patients were treated using Cobalt 60 and 41% using linear accelerator, the median prescribed dose being 27.2 Gy (IQ1-IQ3: 17.6-40.0 Gy), A patient specific voxel-based anthropomorphic phantom with more than 200 anatomical structures or sub-structures delineated as a surrogate of each subject's anatomy was used. The radiation therapy was simulated with a treatment planning system (TPS) based on available treatment information. The radiation dose received by any organ of the body was estimated by extending the TPS dose calculation to the whole-body, by type and localisation of childhood cancer.

RESULTS

The integral dose and normal-tissue doses to most of the 23 considered organs increased between the 1950's and the 1970's and decreased or plateaued thereafter. Whatever the organ considered, the type of childhood cancer explained most of the variability in organ dose. The country of treatment explained only a small part of the variability.

CONCLUSION

The detailed dose estimates provide very useful information for former patients or clinicians who have only limited knowledge about radiation therapy protocols or techniques, but who know the type and site of childhood cancer, gender, age and year of treatment. This will allow better prediction of the long-term risk of iatrogenic events and better referral to long-term follow-up clinics.

Risk Factors for Primary Bone Cancer After Childhood Cancer: A PanCare Childhood and Adolescent Cancer Survivor Care and Follow-Up Studies Nested Case-Control Study

PURPOSE

Radiation to the bone and exposure to alkylating agents increases the risk of bone cancer among survivors of childhood cancer, but there is uncertainty regarding the risks of bone tissue radiation doses below 10 Gy and the dose-response relationship for specific types of chemotherapy.

METHODS

Twelve European countries contributed 228 cases and 228 matched controls to a nested case-control study within a cohort of 69,460 5-year survivors of childhood cancer. Odds ratios (ORs) of developing bone cancer for different levels of cumulative radiation exposure and cumulative doses of specific types of chemotherapy were calculated. Excess ORs were calculated to investigate the shape and extent of any dose-response relationship.

RESULTS

The OR associated with bone tissue exposed to 1-4 Gy was 4.8-fold (95% CI, 1.2 to 19.6) and to 5-9 Gy was 9.6-fold (95% CI, 2.4 to 37.4) compared with unexposed bone tissue. The OR increased linearly with increasing dose of radiation (Ptrend < .001) up to 78-fold (95% CI, 9.2 to 669.9) for doses of ≥40 Gy. For cumulative alkylating agent doses of 10,000-19,999 and ≥20,000 mg/m2, the radiation-adjusted ORs were 7.1 (95% CI, 2.2 to 22.8) and 8.3 (95% CI, 2.8 to 24.4), respectively, with independent contributions from each of procarbazine, ifosfamide, and cyclophosphamide. Other cytotoxics were not associated with bone cancer.

CONCLUSION

To our knowledge, we demonstrate-for the first time-that the risk of bone cancer is increased 5- to 10-fold after exposure of bone tissue to cumulative radiation doses of 1-9 Gy. Alkylating agents exceeding 10,000 mg/m2 increase the risk 7- to 8-fold, particularly following procarbazine, ifosfamide, and cyclophosphamide. These substantially elevated risks should be used to develop/update clinical follow-up guidelines and survivorship care plans.

The risk of valvular heart disease in the French Childhood Cancer Survivors' Study: Contribution of dose-volume histogram parameters

BACKGROUND AND PURPOSE

Valvular Heart Disease (VHD) is a known complication of childhood cancer after radiotherapy treatment. However, the dose-volume-effect relationships have not been fully explored.

MATERIALS AND METHODS

We obtained individual heart Dose Volume Histograms (DVH) for survivors of the French Childhood Cancer Survivors Study (FCCSS) who had received radiotherapy. We calculated the Mean Dose to the Heart (MHD) in Gy, as well as the heart DVH parameters (V_{d Gy}, which represents the percentage of heart volume receiving at least d Gy), fixing the thresholds to 0.1 Gy, 5 Gy, 20 Gy, and 40 Gy. We analyzed them furtherly in the subpopulation of the cohort that was treated with a dose lower than 5 Gy (V_0.1Gy|_V5Gy=0%), 20 Gy (V_5Gy|_V20Gy=0%), and 40 Gy (V_20Gy|_V40Gy=0%), respectively. We investigated their role in the occurrence of a VHD in this population-based observational cohort study using the Cox proportional hazard model, adjusting for age at cancer diagnosis and chemotherapy exposure.

RESULTS

Median follow-up was 30.6 years. Eighty-one patients out of the 7462 (1 %) with complete data experienced a severe VHD (grade ≥ 3). The risk of VHD increased along with the MHD, and it was associated with high doses to the heart (V_40Gy < 50 %, hazard ratio (HR) = 7.96, 95 % CI: 4.26-14.88 and V_20Gy|_V40Gy=0% >50 %, HR = 5.03, 95 % CI: [2.35-10.76]). Doses 5-20 Gy to more than 50 % (V_5Gy|_V20Gy=0% >50 %) of the heart induced a marginally non-significant estimated risk. We also observed a remarkable risk increase with attained age.

CONCLUSIONS

Our results provide new insight into the VHD risk that may impact current treatments and long-term follow-up of childhood cancer survivors.

Risk Factors for Heart Failure Among Pan-European Childhood Cancer Survivors: A PanCareSurFup and ProCardio Cohort and Nested Case-Control Study

PURPOSE

Heart failure (HF) is a potentially life-threatening complication of treatment for childhood cancer. We evaluated the risk and risk factors for HF in a large European study of long-term survivors. Little is known of the effects of low doses of treatment, which is needed to improve current treatment protocols and surveillance guidelines.

METHODS

This study includes the PanCareSurFup and ProCardio cohort of ≥ 5-year childhood cancer survivors diagnosed between 1940 and 2009 in seven European countries (N = 42,361). We calculated the cumulative incidence of HF and conducted a nested case-control study to evaluate detailed treatment-related risk factors.

RESULTS

The cumulative incidence of HF was 2% (95% CI, 1.7 to 2.2) by age 50 years. The case-control study (n = 1,000) showed that survivors who received a mean heart radiation therapy (RT) dose of 5 to < 15 Gy have an increased risk of HF (odds ratio, 5.5; 95% CI, 2.5 to 12.3), when compared with no heart RT. The risk associated with doses 5 to < 15 Gy increased with exposure of a larger heart volume. In addition, the HF risk increased in a linear fashion with higher mean heart RT doses. Regarding total cumulative anthracycline dose, survivors who received ≥ 100 mg/m² had a substantially increased risk of HF and survivors treated with a lower dose showed no significantly increased risk of HF. The dose-response relationship appeared quadratic with higher anthracycline doses.

CONCLUSION

Survivors who received a mean heart RT dose of ≥ 5 Gy have an increased risk of HF. The risk associated with RT increases with larger volumes exposed. Survivors treated with < 100 mg/m² total cumulative anthracycline dose have no significantly increased risk of HF. These new findings might have consequences for new treatment protocols for children with cancer and for cardiomyopathy surveillance guidelines.

Risk of digestive cancers in a cohort of 69 460 five-year survivors of childhood cancer in Europe: the PanCareSurFup study

BACKGROUND

Survivors of childhood cancer are at risk of subsequent primary neoplasms (SPNs), but the risk of developing specific digestive SPNs beyond age 40 years remains uncertain. We investigated risks of specific digestive SPNs within the largest available cohort worldwide.

METHODS

The PanCareSurFup cohort includes 69 460 five-year survivors of childhood cancer from 12 countries in Europe. Risks of digestive SPNs were quantified using standardised incidence ratios (SIRs), absolute excess risks and cumulative incidence.

RESULTS

427 digestive SPNs (214 colorectal, 62 liver, 48 stomach, 44 pancreas, 59 other) were diagnosed in 413 survivors. Wilms tumour (WT) and Hodgkin lymphoma (HL) survivors were at greatest risk (SIR 12.1; 95% CI 9.6 to 15.1; SIR 7.3; 95% CI 5.9 to 9.0, respectively). The cumulative incidence increased the most steeply with increasing age for WT survivors, reaching 7.4% by age 55% and 9.6% by age 60 years (1.0% expected based on general population rates). Regarding colorectal SPNs, WT and HL survivors were at greatest risk; both seven times that expected. By age 55 years, 2.3% of both WT (95% CI 1.4 to 3.9) and HL (95% CI 1.6 to 3.2) survivors had developed a colorectal SPN-comparable to the risk among members of the general population with at least two first-degree relatives affected.

CONCLUSIONS

Colonoscopy surveillance before age 55 is recommended in many European countries for individuals with a family history of colorectal cancer, but not for WT and HL survivors despite a comparable risk profile. Clinically, serious consideration should be given to the implementation of colonoscopy surveillance while further evaluation of its benefits, harms and cost-effectiveness in WT and HL survivors is undertaken.

Risk Factors for Small Adult Height in Childhood Cancer Survivors

PURPOSE

Between 10% and 20% of childhood cancer survivors (CCS) experience impaired growth, leading to small adult height (SAH). Our study aimed to quantify risk factors for SAH or growth hormone deficiency among CCS.

METHODS

The French CCS Study holds data on 7,670 cancer survivors treated before 2001. We analyzed self-administered questionnaire data from 2,965 CCS with clinical, chemo/radiotherapy data from medical records. SAH was defined as an adult height ≤ 2 standard deviation scores of control values obtained from a French population health study.

RESULTS

After exclusion of 189 CCS treated with growth hormone, 9.2% (254 of 2,776) had a SAH. Being young at the time of cancer treatment (relative risk [RR], 0.91 [95% CI, 0.88 to 0.95] by year of age), small height at diagnosis (≤ 2 standard deviation scores; RR, 6.74 [95% CI, 4.61 to 9.86]), pituitary irradiation (5-20 Gy: RR, 4.24 [95% CI, 1.98 to 9.06]; 20-40 Gy: RR, 10.16 [95% CI, 5.18 to 19.94]; and ≥ 40 Gy: RR, 19.48 [95% CI, 8.73 to 43.48]), having received busulfan (RR, 4.53 [95% CI, 2.10 to 9.77]), or > 300 mg/m² of lomustine (300-600 mg/m²: RR, 4.21 [95% CI, 1.61 to 11.01] and ≥ 600 mg/m²: RR, 9.12 [95% CI, 2.75 to 30.24]) were all independent risk factors for SAH. Irradiation of ≥ 7 vertebrae (≥ 15 Gy on ≥ 90% of their volume) without pituitary irradiation increased the RR of SAH by 4.62 (95% CI, 2.77 to 7.72). If patients had also received pituitary irradiation, this increased the RR by an additional factor of 1.3 to 2.4.

CONCLUSION

CCS are at a high risk of SAH. CCS treated with radiotherapy, busulfan, or lomustine should be closely monitored for growth, puberty onset, and potential pituitary deficiency.

Risk of subsequent primary leukaemias among 69,460 five-year survivors of childhood cancer diagnosed from 1940 to 2008 in Europe: A cohort study within PanCareSurFup

BACKGROUND

Survivors of childhood cancers are at risk of developing subsequent primary leukaemias (SPLs), but the long-term risks beyond 20 years of treatment are still unclear. We investigated the risk of SPLs in five-year childhood cancer survivors using a large-scale pan-European (PanCareSurFup) cohort and evaluated variations in the risk by cancer and demographic factors.

METHODS

This largest-ever assembled cohort comprises 69,460 five-year childhood cancer survivors from 12 European countries. Standardised incidence ratios (SIRs) and absolute excess risks (AERs) were calculated.

RESULTS

One hundred fifteen survivors developed an SPL including 86 myeloid leukaemias (subsequent primary myeloid leukaemias [SPMLs]), 17 lymphoid leukaemias and 12 other types of leukaemias; of these SPLs, 31 (27%) occurred beyond 20 years from the first childhood cancer diagnosis. Compared with the general population, childhood cancer survivors had a fourfold increased risk (SIR = 3.7, 95% confidence interval [CI]: 3.1 to 4.5) of developing leukaemia, and eight leukaemias per 100,000 person-years (AER = 7.5, 95% CI: 6.0 to 9.2) occurred in excess of that expected. The risks remained significantly elevated beyond 20 years from the first primary malignancy (SIR = 2.4, 95% CI: 1.6 to 3.4). Overall, the risk ratio for SPML (SIR = 5.8, 95% CI: 4.6 to 7.1) was higher than that for other SPLs.

CONCLUSIONS

We demonstrate that beyond 20 years after childhood cancer diagnosis, survivors experience an increased risk for SPLs compared with that expected from the general population. Our findings highlight the need for awareness by survivors and their healthcare providers for potential risk related to SPL.

Breast Cancer, Secondary Breast Cancers in Childhood Cancer Male Survivors-Characteristics and Risks

PURPOSE

Male breast cancer (MBC) is uncommon, accounting for less than 1% of all breast cancers. Secondary breast cancers among childhood cancer survivors have been well described in the literature, but less is known about MBC.

METHODS AND MATERIALS

We carried out an analysis in a cohort of 7019 five-year survivors of a solid childhood (aged ≤20 years) cancer treated in France before 2001 and followed for an average of 20 years and compared breast cancers occurring in both men and women.

RESULTS

Among the 7019 survivors, 4 out of 3893 male survivors developed breast cancer, compared with 99 out of 3126 female survivors. All of the men had a history of radiation therapy. The 4 men with MBC had estrogen receptors and 3 had progesterone receptors.

CONCLUSIONS

MBC is a rare second malignancy among childhood cancer survivors. Receipt of radiation therapy is a recognized risk factor, but more data about eventual genetic mutations are necessary. Regular screening based only on a history of radiation therapy is not recommended; however, attention must be given in the case of suspicious symptoms.

Retrospective methods to estimate radiation dose at the site of breast cancer development after Hodgkin lymphoma radiotherapy

BACKGROUND

An increased risk of breast cancer following radiotherapy for Hodgkin lymphoma (HL) has now been robustly established. In order to estimate the dose-response relationship more accurately, and to aid clinical decision making, a retrospective estimation of the radiation dose delivered to the site of the subsequent breast cancer is required.

METHODS

For 174 Dutch and 170 UK female patients with breast cancer following HL treatment, the 3-dimensional position of the breast cancer in the affected breast was determined and transferred onto a CT-based anthropomorphic phantom. Using a radiotherapy treatment planning system the dose distribution on the CT-based phantom was calculated for the 46 different radiation treatment field set-ups used in the study population. The estimated dose at the centre of the breast cancer, and a margin to reflect dose uncertainty were determined on the basis of the location of the tumour and the isodose lines from the treatment planning. We assessed inter-observer variation and for 47 patients we compared the results with a previously applied dosimetry method.

RESULTS

The estimated median point dose at the centre of the breast cancer location was 29.75 Gy (IQR 5.8-37.2), or about 75% of the prescribed radiotherapy dose. The median dose uncertainty range was 5.97 Gy. We observed an excellent inter-observer variation (ICC 0.89 (95% CI: 0.74-0.95)). The absolute agreement intra-class correlation coefficient (ICC) for inter-method variation was 0.59 (95% CI: 0.37-0.75), indicating (nearly) good agreement. There were no systematic differences in the dose estimates between observers or methods.

CONCLUSION

Estimates of the dose at the point of a subsequent breast cancer show good correlation between methods, but the retrospective nature of the estimates means that there is always some uncertainty to be accounted for.

Thyroid Radiation Dose and Other Risk Factors of Thyroid Carcinoma Following Childhood Cancer

CONTEXT

Thyroid carcinoma is a frequent complication of childhood cancer radiotherapy. The dose response to thyroid radiation dose is now well established, but the potential modifier effect of other factors requires additional investigation.

OBJECTIVE

This study aimed to investigate the role of potential modifiers of the dose response.

DESIGN

We followed a cohort of 4338 5-year survivors of solid childhood cancer treated before 1986 over an average of 27 years. The dose received by the thyroid gland and some other anatomical sites during radiotherapy was estimated after reconstruction of the actual conditions in which irradiation was delivered.

RESULTS

Fifty-five patients developed thyroid carcinoma. The risk of thyroid carcinoma increased with a radiation dose to the thyroid of up to two tenths of Gy, then leveled off for higher doses. When taking into account the thyroid radiation dose, a surgical or radiological splenectomy (>20 Gy to the spleen) increased thyroid cancer risk (relative risk [RR] = 2.3; 95% confidence interval [CI], 1.3-4.0), high radiation doses (>5 Gy) to pituitary gland lowered this risk (RR = 0.2; 95% CI, 0.1-0.6). Patients who received nitrosourea chemotherapy had a 6.6-fold (95% CI, 2.5-15.7) higher risk than those who did not. The excess RR per Gy of radiation to the thyroid was 4.7 (95% CI, 1.7-22.6). It was 7.6 (95% CI, 1.6-33.3) if body mass index at time of interview was equal or higher than 25 kg/m(2), and 4.1 (95% CI, 0.9-17.7) if not (P for interaction = .1).

CONCLUSION

Predicting thyroid cancer risk following childhood cancer radiation therapy probably requires the assessment of more than just the radiation dose to the thyroid. Chemotherapy, splenectomy, radiation dose to pituitary gland, and obesity also play a role.

[Biosynthetic growth hormone extracted from mammalian cells used in the management of growth hormone deficient children]

Biosynthetic growth hormone extracted from mammalian cells was used in eight children with growth hormone deficiency, in search for a clinical safety study. Each child received 0.6 U/kg/week, subcutaneously, during a period of six months, and was evaluated monthly for clinical, anthropometric and laboratory modifications induced by the drug in a physiological or pathological way. The growth velocity increased from less that 4 cm/year to 11.2 +/- 1.08 cm/year, the bone age maintained according to the chronological age, and the anthropometric evaluation showed an harmonious and physiological growth. There was not any undesirable nor secondary changes except transient hypothyroidism in two patients, and unmasked hypophyseal hypothyroidism in another two. We concluded that biosynthetic growth hormone extracted from mammalian cells is a safety drug, and that patients with growth hormone deficiency may be treated with it in order to improve their final height expectancy.